Every engine part changed, still has P0171 P0174 codes Pt1

1998 Ford F150 Triton V8 with P0171 and P0174 lean codes that has had every part thrown at it and even the repair shop can't figure it out...
But maybe a DIY can.
See my website and download the Free DIY Diagnostics Book (during limited time only) at www.schrodingersboxqm.com!!
Part 2 is Here: • Every engine part chan...

[@jasonmurdoch9936]

I love it when you said no way they'll take it to a shop because they don't know what they're doing and they don't trust the mechanic with their car while I can definitely agree with him because 99% of the time they're absolutely correct

[@KarlHamilton]

Had this on my Jaguar XJR. The specialists told me to cut my losses and get rid of it but I persisted. It was the fuel pressure regulator, the diaphragm was leaking. That was a good day.

[@Drew-Dastardly]

It's bad grounds. I can see it from here, sitting in my lawn chair sipping an iced tea while watching you struggle.😉

[@SchrodingersBox]

ROTFLMAO!!!!

[@raycook1503]

I diagnosed mine by watching fuel trims when I sprayed brake clean around the intake. They shot way down and replaced lower intake. Solved the problem.

[@SchrodingersBox]

Yep- or just use fuel trims to see if that would even work in the first place.

[@OzFrog48Z]

I remember those era ford trucks with lean codes had a vacuum hose in the back of the throttle body that went to the PCV system that would get sucked in and cause a vacuum leak. Was vey common. It was a big enough leak that it would affect fuel trims even under a load. Also people would forget to replace the breather hoses from the valve covers to the air intake system duct after working on the engine.

[@SchrodingersBox]

Yep- would have considered that if I had a vacuum leak but we know it wasn’t.

[@Z14kt12timandjes1]

Excellent information as always! Thanks! On my Autoengenuity, if I go to the live data grid tab, it will allow me to change the MAF to display in grams per second.

[@crasher88]

to test the voltage out put of an analog MAF sensor you have to hook it up to a scope. When you do a snap throttle test the MAF should put out close to 4 volts as you side but it is highly unlikely you will see it on scan data. The scanner updates too slowly and there is too much latency on the network to update the voltage quick enough for you to see the MAF voltage accurately.

[@jeremyrainwater2175]

Since my grandfather died I believe God sent me to you to finish learning. 😢. Ty Lord Jesus!! I subscribed. My grandfather taught me so much. I'm just disabled from juvenile diabetes. Man I love this channel. I've learned a lot already. Especially the Ford Ranger!!! Ty!!!! God bless you and your family!!

[@SchrodingersBox]

How nice!! Thank you. I hope you continue making your grandfather proud!

[@victorm9283]

Just a Suggestion... Anybody check the plastic bushing on The IMRC (Intake Module Running Control) It's been my Experience they brake constantly. Causing a P0171/P0174 reading. Lean reading on Bank 1, sometimes on both Banks.

[@paulwilliams7427]

I love a good murder mystery.....

[@SchrodingersBox]

This one won’t disappoint!!

[@LeverPhile]

Colonel Mustard did it in the library.

[@gbrielbuis6333]

Happy it didn’t turn into a suicide haha

[@mph5896]

I had a few of those trucks throughout the years, 2001 with 5.4l 4wd, had a bi fuel system on it with Natural gas or gasoline. Also had a 1997 with the 5.4l. Both great trucks. The 2001 rusted away, I sold it for parts when the trans went at 150k. Sounds like the truck had multiple problems when Brought to the shop. Fuel pump def sounded like the drivability issue. Then its just fixing a CEL on a 25 year old truck after somebody parts cannoned a crap ton of (I would assume) cheap parts on it. What can go wrong🤣

[@tianyi1240]

IMPORTANT: please help respond to me. To continue with the p0171/0174 problem on Highlander V6. 1) I realized that I only cleaned the IAT sensor but never cleaned the MAF wires. After cleaning the MAF wires, trim numbers improved a lot. Idling LTFTs decreased from -20% to -13% and -10% respectively. Trim numbers are all with +-5% when slowly accelerated to 3200RPM. However, when the peddle is pressed abruptly, I can see again LTFT1&2 goes up to 30% transiently. I checked my other car, a Corolla, this does not happen. So, there is still a problem. 2) I finally connected the fuel pressure gauge again so that I can see it from the driver seat. The pressure is alway at 46psi at idle and when slowly accelerated to 3200RPM, no change in the pressure. When I abruptly press the gas peddle, it slightly moved a bit to 44psi transiently. No big change at all. 3) Measuring the MAF voltage is a bit challenging to me. I do not have the needles you used to probe the wires and I'm afraid of frying my ECM. I ordered a Denso MAF sensor for this car which was only about $50. I'd rather spend the money to avoid being prevented from highway trips. I have already spent more than that on the pressure gauge and related material. Please give me some advice!

[@jeremyrainwater2175]

God bless!!! Brother I love your videos!!!!!!!!!!

[@brianw8963]

Evidently more info to gather fuel pressure for sure and tps would not hurt to at least check. Parts cannon being blasted, check on the ammo for sure.

[@TheCowgirlNiamh]

Will be interesting to see how this turns out! I’d have concerns about the parts he used and whether they’re OE or eBay specials. I’m confident you’ll get to the bottom of it Matt 👍🤗

[@ACommenterOnYouTube]

i didn't watch the entire video but several yrs back he had a hyundai with a lean condition on bank 2 which was the back side 3 cylinders. Same thing, ALL parts changed out, still lean. Come to find out it was low compression on the middle of the 3 pistons. Less compression from that piston = less air suction which means less air intake over-all which tells the ecu that its not breathing as good which means the ecu will drop less fuel per cylinder because it see's less air from the MAF ... due to the 1 low compression piston. Now that less fuel with GOOD compression pistons = lean condition.

[@SchrodingersBox]

Thanks as always Niamh!

[@wolfnorth7075]

To me, your video is better than movie, than news, because your videos are REAL. Thank you.

[@SchrodingersBox]

Hahahahahah. Hey- some movies are real lol.

[@clutch5sp989]

The rubber grommet thru the air intake tube for the MAF sensor was loose on mine and had me searching all the wrong places for a vac leak.

[@georgebonney90]

Hey buddy I hope you had a great Christmas God Bless

[@SchrodingersBox]

Hey you too George!!

[@Pablo_Automotive]

Nice video Matt, I hope that you have a great New Year

[@SchrodingersBox]

Thank you my friend from Spain!!

[@denrayr]

Cool case study! According to Google 0.44 lb/min converts to 3.326g/sec. Using the rule of thumb that you should have ~1g/s per liter at idle, it seems like the mass air flow sensor is under reporting the amount of air entering the engine. If correct, this means the computer would be using the fuel table for the engine running at a lower rpm and is having to raise the fuel trims to compensate. I look forward to part 2!

[@SchrodingersBox]

Hahaha I have learned to expect nothing less from you, Dennis. I like the logic.... we shall see!

[@mrfishbulb7187]

Well done. I was trying to recall that general Maf formula but got a little confused when converting from lbs/min to g/min and not getting a correlation to engine litre size. I'd forgotten to divide by 60 seconds which would've put me in the ball park. Every day's a school day!

[@kerryb2689]

@@SchrodingersBox Pretty easy to remember 454 grams per lb and 60 seconds per minute. 0.49 lb/min x 454 g/lb / 60 sec/min = 3.7 g/sec ... way too low. Multiply the numbers to cancel the units as needed.

[@SchrodingersBox]

Yes but how are you calculating the margin of error from the lb/min starting calculation. That’s my concern.

[@denrayr]

@@SchrodingersBox for the purpose of using the rule of thumb of 1g/s per liter at idle, we're already in margin of error territory. It should all be taken with a grain of salt. I would say it should only be used to give direction. Your test methods of unplugging the sensor to see how it would work with substituted values and using the scope to test the performance were the real determining factors that the sensor was bad. Just out of curiosity, which Triton engine did this truck have? The 5.4 or the 4.6? If it's the 4.6, that's pretty neat because the conversion to g/s came in around 4.7 after the fix (if memory serves. I watched it last night). If it has the 5.4, it really proves that this should all be considered carefully before changing any parts.

[@jasonputtock4428]

Im taking a shot in the dark at 8 mins 02 secs. As for he list of parts. Im shooting for the fuel filter. Too lean condition. They did pump and improved. Im considering the filter now. O2 would be my first check for 100% but this is interesting case. Im gonna keep watching.

[@sheerwillsurvival2064]

Let the games begin 🤗👍🏻

[@ACommenterOnYouTube]

You had this issue YEARS ago with a Hyundai ... Turned out was low compression on one of the back side pistons, low compression meant less air intake which in tern leaned out the good compression cylinders because the ecu would only inject enough fuel for what the engine was "breathing" in ... That less fuel for a good compression cylinder = lean condition.

[@SchrodingersBox]

Yes however this car does not have a compression issue. It’s clearly an induction metrics issue.

[@DependableAutoTruck]

i bought auto Enginuity years ago and upgraded years ago looks like the have for android now do you know if the program has improved in the last 3 years where it competes with like the launch and other tools

[@mrkeso41]

I have both theses codes and I have replace the motor and I still have the same codes and the only thing I didn’t change was the fuel injectors and the intake manifold but did replace all the gaskets and put some shorty headers on it and it has a “cold air intake” so I’m not sure if that’s what’s causing the problem but then again it already these codes before I put one on.

[@mrkeso41]

To pass inspection I sprayed mass flow air cleaner and it would get rid of the code for about 100-200 miles before it came back again

[@SchrodingersBox]

Not sure I follow- why did you replace all those parts for this code?

[@UZCOexcavationexperience]

My truck is the 2005 w/ 4.6 my trims get better under load. What grams per second should a maf on this vehicle?

[@DylanL69]

Depends on the size of the engine

[@joegomez478]

Fuel filter?😊

[@rosewd2]

On the gm sensors with the screen on one end and an aluminum housing with the sensor between them. 97 camaro. a lot companies make a replacement housing wo the screen and ported out. I tried one of those and it threw the fuel trims off by +10. The housing and sensor are matched. now im sure the granitelli sensors wo the screen and ported housing work because the sensor is recalibrated to work with that housing. They also need to know if its a cold air intake or not. my camaro is an SS so it pulls air thru a hood scoop. So im thinking that maf sensor is different than the z28 that pulls air from an inside air box.

[@SchrodingersBox]

Yes that screen is to create laminar flow for the sensor to work. People who remove it thinking it’s an air obstruction actually lose power.

[@joshuapruden6497]

I am leaning to a under reporting MAF. Here is how I figured it out- The engine is a 5.4 Triton. The MAF says it is only flowing .44 LBS/Min. That seems low to me. I looked into calculating it to grams per second. (.44 x 7.56) to get the grams per second. It comes out to 3,3264 Grams per second. It is supposed to be around 5.4 G/s. I also noticed the BAro PID seems low. 154Hz is only for about 1500 feet above sea level. If the Baro PID reads around 157Hz that would suggest about 29in-HG Crown Vic had a problem similar to what is being shown in the video see Ford TSB 05-3-1 Go to the last page. It has a chart that I used to get my bet that the MAF has a manufacturing defect. I cant wait to see what the fix is for this.

[@SchrodingersBox]

Impressive!!

[@The_Noticer.]

I was asking the same throughout. Especially if it was replaced by a non-OEM sensor to save costs.

[@jdtractorman7445]

It's a 4.6L Triton. When Ford came out in 97 with those trucks, the 4.6L had 2 coil packs each firing four plugs. The 5.4L had coil on plug ignition throughout its existence. The 4.6L got coil on plug ignition I believe in the 99 model year just like the 5.4L already had. Yeah, the MAF seems slightly low with the calculation.

[@joshuapruden6497]

@@jdtractorman7445 Its still under-reporting. lol

[@hashirnawaz4532]

Hej How are you Are you now about Citroën c4 Grand Picasso 1.8 petrol i have same problem

[@PanSlayah]

Had this same issue on my father in law truck. Was the manifold gasket.

[@SchrodingersBox]

how could you have had positive fuel trims under load then???

[@calholli]

(I'm 5min in) -- My first guess is a shotty MAF, and it's giving out of spec readings; Hopefully he kept his old parts and you can throw the OEM back on there. lets see. ;)

[@richardcranium5839]

did you reset the KAM? or was that done before??? if it was reset it should immediately go to zero. or is it a scan tool thing? that just isnt clicking for me. had a few that ny scanner said it reset but actually didnt unhooked the battery cables then shorted the plus to minus to drain the ecm capacitor and it went to zero like it should

[@SchrodingersBox]

It was done before.

[@egladmansr1]

The air intake maybe loose solved my problem

[@dereksimenac8844]

Everyone always overlook the catts when diagnosing the trim issues. If there is no MAF I'd be checking the temperature sensors because if they fail without throwing a code they will read -40 causing the engine to pour the fuel to it

[@SchrodingersBox]

A CTS at -40 will show an open code on any vehicle but what I don’t get is how is a cat going to cause a fuel trim lean code??

[@donkempfer4803]

09999⁹9999999999⁹

[@misterbulger]

Brand new O2 Bank 1 sensor 1 reading zero volts unplugged while connected to my meter. It has a new MAF, new coilpacks, fuel pressure is spec, tried spraying every nook and cranny but no vac leaks... car drives ok but down on power. Fuel trims are high. Will try resetting the memory... only thing left is very expensive injectors, unless its a valvetrain or timing issue?

[@SchrodingersBox]

if its unplugged and reads zero on meter it is clearly missing bias voltage. I am confused on why change the MAF, and coil packs and especially injectors- was there also a induction metric and ignition fault? I miust be missing something but what did you do for the bias voltage?

[@misterbulger]

@@SchrodingersBox one bank reads zero other bank reads low volts. Because it's actually very lean I suspect. Trying to figure it out.

[@SchrodingersBox]

No read the bias voltage with key on only.

[@zecatela]

Curious, who's the manufacturer of the MAF sensor that the owner replace it with? I remember hearing those items are sometimes particular with using an aftermarket MAF sensor than the official Ford one or Motorcraft version. Just a thought.

[@SchrodingersBox]

We look at the MAF in part 2 … the MAF was aftermarket and did not have a manufacturer shown- it had a QR code label on it but I didn’t use it to find manufacturer.

[@billsmith2212]

Diagnose Dan put an aftermarket MAF sensor on the scope . He compared it to an OEM . The aftermarket was off by a third ! Imagine several low end parts and is it a surprise the vehicle doesn't run well ?

[@brianw8963]

@@billsmith2212 And it sounds like a lot of aftermarket parts, nothing like installed variables to make it interesting.

[@vieczurable]

I had to have two new cheap faulty MAFs before I went for expensive OEM however shouldn't just disconnection replace bad values with default expected ones so we could see better trims if MAF is to blamed? No everybody can get detailed specs for a vehicles sensors.

[@LeverPhile]

When he said MAF had been replaced by owner, my first thought was cheap aftermarket.

[@Neal-ip1ng]

Got a Chevy Colorado 2005 everything new on truck run good today ran great new all new under hood 15 k in to it all new an got scan tools got p171 light came on an off then truck i park it now truck turns over but want crank any help or ideas let me no ill even ship the truck to u

[@TheOnespeedbiker]

LOL When you questioned replacing "both coils", most the cars I have owned it would have been "the coil".

[@SchrodingersBox]

Yes it definitely confused me lol.

[@tianyi1240]

Big fan of your intelligent approach to diagnosing car problems. Not sure if you will answer me under this 7-month old video of yours. If you can tell me what could be wrong with my 2002 Highlander V6 engine, I'd greatly appreciate. Codes: p0171/p0174 typically occur after long time highway driving (> 4 hours) with 2 identical pending codes. No noticeable drivability issue. No abnormal symptom. Never occurred in city driving and never occurred when driving 150km round trip at 110km/h max speed. Fuel trim readings normal or rich when idling and driving at low speed or accelerate slowly to a higher speed. LTFTs jump to high positive levels (easily 20-30%) when gas peddle is pressed hard even when parked. The readings can go as high as 40% temporarily when further accelerated from 110km/h to a higher speed. Immediately at the release of the peddle, the fuel trims switch almost immediately to negative values (-10 to -20% easily). What could be wrong? If it is due to low fuel pressure, why didn't I notice other symptoms associated with it? I still think a measure of the fuel pressure is a must follow up now.

[@SchrodingersBox]

sounds like either a low fuel pressure issue or a dirty MAF sensor to me the way you describe it.

[@tianyi1240]

@SchrodingersBox Thanks a lot for your prompt response. Nothing changes after I cleaned MAF sensor although I'm not sure if it has failed. Live data show that the numbers change from low g/s to high g/s when gas peddle is pressed, but not sure if the numbers agree with specifications. Should I see other symptoms if the fuel pressure is low? Why is the driving ok, can easily accelerate to 140km/h on highway? Have no trouble passing slower cars.

[@SchrodingersBox]

I would look at fuel pressure and also at the voltage on the O2 sensor at WOT next then.

[@tianyi1240]

@@SchrodingersBox Thanks again. Need to buy fuel pressure tester and waiting for it to come. Still do not know if it is bad fuel pump, clogged fuel filter, or bad fuel regulator. All of them are in the fuel tank. But my symptoms seem to be so mild, no starting problem, no driving problem, very different from symptoms others describe when one of the above fails. The upstream o2 sensor on bank 2 was replaced a few years ago with an after market one, could that be the problem?

[@tianyi1240]

@@SchrodingersBox Ok, one more question: can a failed downstream O2 sensor create lean code? A cheap OBD2 tool reported that o2s12 min voltage was 0.02v below the 0.105v min value, and max voltage was 0.64v also below the min value of 0.73v. The status for both were reported as FAIL. Sorry I have trouble with the correct fittings to connect fuel pressure gauge to fuel line. So no test yet. But my intuition is the pressure should be ok because I have zero trouble with idling and drivability of the car.

[@82_KID]

0:54 "is... Failure to Communicate!"

[@mrsmith7751]

Those so called expert mechanics had me pay them over 500 to replace the MAF sensor off course I didn't know it at the time and the check engine still came back. They said they could look for other problems and off course keep charging me until they figured it out. This is why we don't trust the e parts. Turned out they installed a cheap MAF sensore and replacing it was the fix.

[@joeblow6786]

There is definitely, definitely, definitely, no logiiiic in human behavior.. Idk if you're a Bjork fan but you definitely, definitely, definitely sounded like her for a second there. Just a little too much fun at your expense Matt.

[@SchrodingersBox]

I love Bjork - I only know her human behavior song though lol.

[@joeblow6786]

She had her effect on you... Definitely!

[@dicktomasko1553]

I would have tried a little loading whilst in gear...and put a gauge on FP first. Also FP was prob first problem but fired the cannon with aftermarket parts and may have a bad one...causing another issue now.....looking forward to pt 2...

[@thecardoc100]

BARO is a calculation that is based on the reported airflow from the MAF sensor at given engine RPM and throttle openings. They just happen to make it display in Hz scale that keeps it consistent with previous systems that used either the digital MAP sensor or an actual Baro sensor. You will have to drive this with a fairly heavy throttle and low rpm to see the BARO pid update. That BARO calculation is important with these systems because it is part of the base fuel injection pulse calculation. If the system get's that wrong, fuel trims do have to adjust for it. You haven't had fun until you have a vehicle that recalculates the BARO differently on successive accelerations with some of the events underreporting the airflow and some overreporting the airflow and the cause is turbulence in the airstream where the MAF is located. I have had these trucks where the air filter was less than three months old but had been sucking the dust up at some construction site to the point that the filter was crushing under the airflow and that resulted in the cause of the turbulence. The rear fuel trim you saw in the data stream is something that you should have checked. That is based off of just the downstream sensors and has to be added in with the short term and long-term trims to know the actual total fuel trim. This brings into play the fun topic of "What does an oxygen sensor sense?" Have you measured the alcohol content of the fuel?

[@SchrodingersBox]

Good thought however an incorrect fuel alcohol content won’t cause that inconsistent pattern we saw on the fuel trims.

[@thecardoc100]

@@SchrodingersBox That's true but it is still part of the routine especially when we are seeing high positive trims.

[@tubetime39]

John Gillespie: that's what I was thinking.... NOT, meaning me thinking the same. Thanking you and Schrodinger here ! I am just now trying to learn this stuff and you guys impress me very much. I can see why most techs don't know enough about these things, so complex. Ironic, I was just reading about MAF, BARO MAP & such last night. Thank You for sharing !! I have a long ways to go but even knowing some of this will be helpful and fun at my age.

[@thecardoc100]

@@tubetime39 You saw me refer to the turbulence that can affect the sensor's ability to accurately measure the air flowing past it. We have had cheap air filters put into these air cleaner assemblies where the plastic cone that is bonded to the inlet side of the filter is off center. That mislocation of that cone disrupts the laminar flow of the air past the sensor differently at various engine loads and makes figuring out what is wrong a real challenge.

[@jamesmarsh1831]

These engines have a problem with a cracked or broken when worse running pcv line at the very back of the throttle body that is hard to see and get to.

[@SchrodingersBox]

Yes I heard that. But of course I know that’s not possible to be the issue here so I didn’t worry about it.

[@colonialroofingofnorthcaro441]

I did my truck like that but I replaced all the parts cuz I just wanted to redo everything I didn't have any intentions of getting rid of my truck I love my truck so I just done an overhaul and just replaced everything in made it all new it ain't always about just throwing money and parts at it and sometimes it's just this is all I want I still love this truck and I just want to make it like new again which is replacing it with new parts and so some people namely myself do it for just that reason which is the reason I done that I replaced everything cuz I wanted my truck to be like brand new anything that has failed anything that was broke and anything that wasn't broke I replaced it brand new cuz I was just over hauling my truck tonight cuz I want to keep it and I like it keep on keeping it but I was just making a point there, some people do it because it's new and it's their vehicle in their mind putting it in there I've always looked at it like I've got an extra part now that hopefully will last another three hundred thousand miles cuz that's how many miles I have on my vehicle and if I can get 600002 and I'll be replacing parts to get their guarantee you but every part I put on it just gets a newer and newer

[@SchrodingersBox]

I think you forgot to put a period at the end of that sentence.

[@UZCOexcavationexperience]

You should explain the Egr trick better

[@oldbiker9739]

muffler bearings ???

[@HouseCallAutoRepair]

My left arm guesses cam timing, my right arm says carboned up intake. My chair is guessing clogged cats... My brain says look at running, in cylinder pressure pressure waveforms...

[@HouseCallAutoRepair]

Completely dropped the ball...I eas thinking the complete opposite, in the sense I was thinking too rich, not lean.

[@mauricioandrade2563]

To check the egr valve, did you blow into it or suck?

[@unstableminded]

suck to create a little vacuum which closes the diaphragm.

[@kristhomas6474]

I missed it because of California emissions.

[@hasibquraishi1403]

i have a 2006 toyota 4runner v8 4.7 thats giving me p0174 and p0171 i have changed the MAF sensor and did a visual test for leaks and check the PCV value all were ok, vehicle runs fine but the check engine is on, fuel trims are very high Long term 30+ and short term 20+, i would like to bring my car to you and have you check and fix if you have time, I already emailed you as well thanks alot

[@SchrodingersBox]

I never got your email. Send it to [e-mail]

[@hasibquraishi1403]

@@SchrodingersBox it was different email, i resent it to this email

[@TheGb50]

I went trew the same thing with my 98 mustang gt same codes

[@wayned3137]

I don’t know what’s so hard that these lean codes driving people crazy. A few things that cause these code. Start with most simple things first and you don’t even need to open the hood to find out if it has vacuum leak condition or weak fuel pump base on fuel trim readings assuming your o2s are working correctly.

[@SchrodingersBox]

So how would you have found what this issue was without even opening the hood, exactly? Please explain.

[@thecardoc100]

@@SchrodingersBox A lean condition caused by a vacuum leak "after the throttle plate" will make its largest correction at low speed, low load. So Idle, in park/neutral large correction. Speeding the engine up similar to what you did in the video allows for less time for the leak to impact the air/fuel ratio but you still have significant manifold vacuum, in fact the vacuum might be higher than it was at idle. That means you will still have a correction adding fuel but it would be less. In practice we do this check at idle, 1500rpm, 2500rpm and 3500rpm and record the results. Then the next step is to do this under load, in gear against the brakes or on the road if necessary. So put it in gear and note the correction at idle. It should still be making a significant correction. Then increase the engine speed to 1500rpm against the brakes and transmission. The throttle is now letting a lot more air into the engine, manifold vacuum will be very low. Compared to the air going through the throttle the vacuum leak is now insignificant so the fuel trim corrections should be minimal compared to what they were at idle. Now go to the higher rpms and see what the correction is, again you may have to drive it depending on the stall speed of the torque convertor or if the vehicle is a manual transmission. A vacuum leak after the throttle plate will have "little to no effect" on the air fuel ratio when there is no manifold vacuum. Now consider what exactly you see if it is a torn boot between the MAF and the throttle plate with this same routine (no load, versus load). What would you see if it was incorrect alcohol content? What would you see with a skewed MAF? How about one cam out of time or a restricted exhaust on one side? A weak fuel pump, or restricted fuel filter? How does all of this change if the system is a speed density (MAP) versus a MAF? It is correct to say that you might not always know exactly what is wrong, but you can eliminate possibilities from the road test or just sitting in the bay before the hood is opened. Then again depending on the behavior of the vehicle you happen to be investigating there have been many that there was no question what was wrong without opening the hood. Now reverse this and imagine false fuel (e.g. Leaking fuel pressure regulator) FWIW in the last decade we also now have vehicles that fail to follow what would be expected when using the above routine that has worked for more than twenty years. That forced us to keep more variables in play and is too much to discuss here.

[@carlodonnell146]

Why would one change coils for a lean condition; do they have anything to do with a lean condition that I may not know of. If I had a lean condition I would not think of coils.

[@SchrodingersBox]

I don’t know why anyone would change coils for any condition other than the coils are bad. But in the case of a misfiring coil that would cause the LTFT to show a lean exhaust. maybe that’s their thinking? honestly I wouldn’t even credit them that much lol. It’s probably more “check engine light’s on. Guess I better change plugs wires o2 sensors and coils…”

[@carlodonnell146]

@@SchrodingersBox I suppose the coils could indicate a lean condition then, I'm learning!

[@SchrodingersBox]

Yes what happens is if the coil doesn’t work, you don’t get combustion in that cylinder. The O2 sensor sees that unburned oxygen and reports lean!

[@ricardoflores8934]

Yes no what! Please answer your questions! Just give me ford techmakuloca😂

[@javiercadena206]

Wth!! What was the problem...

[@dennissalisbury496]

P0171 P0174 codes mean Bank 1&2; whatever is happening, affects both banks simultaneously?

[@SchrodingersBox]

That’s correct. HOWEVER you must be careful- if you have a P0171 but not a 0174 you still need to check the trim on bank 2 because it may be just under threshold for the MIL. In fact I have a video of this. So you still approach it as a whole engine issue even though only 1 bank codes.

[@dennissalisbury496]

@@SchrodingersBox DTC is P0000 lamda control adaptation fault Bank 1&2 last occurrence plausibility

[@LeverPhile]

@ 19:05 "How does it know the barometric pressure?" Fwiw, on e46/e39 BMW's (1997 to 2006-ish) that have MAFs but no MAPs, there is a barometric pressure sensor integrated directly on the DME circuit board (the ECU in BMW-speak). I am sure other cars have similar setups (assuming the ECU is not sealed air tight). If the scan tool is showing atmospheric pressure, then that data must be coming from somewhere.

[@SchrodingersBox]

You are correct. The barometric readings are indeed from the MAF on this model.

[@thecardoc100]

I explained this system in one of the other responses. Under specific conditions (low engine speed and wide throttle opening) the measured mass airflow is checked against known airflow rates written into the software. The computer then uses this inferred value as a BARO input. There is no BARO or MAP sensor in this system.

[@LeverPhile]

@@thecardoc100 Perhaps on this car, but on the BMWs I referred to above, there is in fact a BARO sensor found/hidden as a component on the ECU circuit board. How it is used is unclear (perhaps a backup for a bad maf?), but it does exist. Other cars may or may not have this; I was just pointing out it's potential existence as a source of the BARO pid info. I understand very well that a maf can calculate air mass without a pressure reference, but BMW included an actual BARO sensor for some reason, and others likely do as well.

[@thecardoc100]

@@LeverPhile The use of a BARO sensor is not exclusive to BMW and it is common for it to be mounted to the board of the ECM/PCM when it is used. We just have to understand there are other ways to get the same information. For example, there are a number of Speed Density systems that look at the MAP sensor signal at start-up and then again under specific engine RPM and throttle openings to see (update) what the atmospheric pressure is. As far as what this information is used for goes, that's what you find out when you attend training classes. Some of the uses are obvious if you just think it through. The first one is the BARO reading infers altitude. The higher in altitude the vehicle is less dense the air is and the less oxygen there is in the air. So that becomes part of the base fuel injection pulse width calculation. It's also going to compensate the spark timing map. It's often used as a cross reference for accuracy of both the MAP sensor and the fuel tank pressure sensor when used. Plus it's used to enable or block specific tests from running such as portions of the Evaporative Emissions System Monitor. There are more uses for this value these are just a few of them.

[@888snuffy]

probably a loose fuel cap. :)

[@aymenmohamed1134]

👍🏻👍🏻👍🏻

[@williamhanna5224]

2 injectors dirty or need replacing

[@SchrodingersBox]

why two??

[@AJourneyOfYourSoul]

After you started it up, said it runs good, but everybody says drivability is terrible, ie when under load, my guess........ Clogged fuel filter. These trucks have a replaceable fuel filter on the driver side frame rail, and NO ONE, ever changes them, ever.

[@SchrodingersBox]

That’s because fuel filters seldom if ever clog. I have yet to see a clogged filter even with a failed pump. The pump “sock” gets contaminated long before the filter does.

[@davyarthurs]

Yep makes me laugh too. Someone has just spent hundreds on the parts canon and then wants more silver bullet ideas from others, but not willing to spend less than the cost of the next guess on a proper diagnosis! I wish I understood their logic, as I just done get it

[@SchrodingersBox]

Amen!!!

[@f8ad7n]

P0171 System too lean bank 1 FORD EXPEDITION 2004 5.4L

[@SchrodingersBox]

what’s the fuel trim show?

[@andrewerickson6690]

I'm very curious about the outcome

[@joebudi5136]

So what was the problem and was it fixed?

[@stefeniebustamante9380]

Yes it was fixed.. maf sensor... it's in part 2

[@joebudi5136]

​@stefeniebustamante9380 So was that part replaced and was no good? OR did he never replace the sensor?

[@stevek3036]

I would suggest its ignition related

[@SchrodingersBox]

I never saw any evidence pointing to ignition- what did you see that suggests that?

[@user-fe1uj6ft2l]

😊😊

[@embreesmith7613]

MEOOOOOW. 😀

[@danstiverson]

Could this be exhaust clog? Maybe someone put leaded fuel in sometime

[@SchrodingersBox]

Not with the MAP sensor readings. We see there is no backpressure.

[@embreesmith7613]

HIT THE THUMB UP PLEASE. IT HELPS THE CHANNEL

[@jasonputtock4428]

Gah, it finished on fuel pressure.... dam it.

[@SchrodingersBox]

Hahahahha!! I was mean. Part 2 is coming in a few minutes.

[@jasonputtock4428]

@@SchrodingersBox Gud dam it you. You tease.!!!

[@pete2170]

Remap ecm bimp timing injector pulse is too wide open .

[@SchrodingersBox]

Based on what data? What data indicates this is the issue? Remember we don’t want to guess- People have guessed enough. Also if pulsewidth is to wide why is it lean and not rich? Please explain.

[@pete2170]

Not enugh fuel pressure

[@pete2170]

Its all dumping back in to the tank

[@SchrodingersBox]

I don’t see how that is possibly happening based on the data we see. the one thing we know for 100% is fuel pressure is not the issue. look at the data and think what it points to….

[@BlindPointman]

I would love to have such diagnostician where i live not like these lazy bastards who piss me off permanently but they take 300 pounds for nothing every time.

[@tubetime39]

A N GameSport: Yep !! The reason I am trying to learn some of this stuff !

[@jerrypeal653]

Older video but gas tank venting not closing off .

[@SchrodingersBox]

Wait- how is that possibly going to cause a lean condition????

[@jerrypeal653]

@@SchrodingersBox vapors get pulled by what means ? I will agree it’s not a likely scenario but it’s a car they don’t understand likely, lol . I’m dealing with the same issue with my grandsons vehicle. MAF is new but under reporting, running smoothly, now to find out why . MAF was just replaced . Fuel trims @25 . Looks like same crap you dealt with in this video. Nice diag by the way .

[@SchrodingersBox]

It’s not possible for open vent valve to do it. It’s always open UNLESS during a evap test. Also what is your data showing an underreporting MAF?

[@jerrypeal653]

@@SchrodingersBox supposed to be closed but I don’t assume solenoids are working properly. 2.3 gs on a 3.0 engine. It responds under advanced of throttle . I’ll probably do a purge and seal test on the tank pressure just to be sure . Thought I should add the vehicle is old 07 and hadn’t been taken care of . Even the OBD connection is just hanging in free space , I’m sure it’s got multiple issues. By the way I’m up in Northglenn been watching your channel for well since well before you moved . You do a good job really enjoy the channel.

[@SchrodingersBox]

No a vent solenoid will be open. A purge solenoid will be normally closed BUT it’s also pulsewidth modulated.

[@greyguy9767]

Vacuum leak, bad fuel injector,bad purge valve. Bad intake gasket.

[@SchrodingersBox]

Based on what data?

[@greyguy9767]

@@SchrodingersBox I assuming bank 1 was lean.

[@SchrodingersBox]

Both banks are equally lean. Even so- why does a lean bank mean the intake gasket is bad, or a vacuum leak, or a bad fuel injector or purge valve. What evidence is pointing to any of those? Why is it not a timing problem? A low compression? A restricted fuel filter? A dirty MAF? Also if it’s an intake leak why are both banks equally lean?

[@greyguy9767]

@@SchrodingersBox a 2014 Cruz I fixed was a partially clogged fuel injector on bank 1 showing lean wich lead to bad ignition coil module from being lean. Intake leak can cause bank 1 and 2 to run lean like a vacuum leak cause it is a vacuum leak. Stuck open purge valve can do the same thing.

[@SchrodingersBox]

Yeah a faulty injector on bank 1 will not have that effect on bank 2. you would see bank 1 trim affected while bank 2 was normal. the fact both banks have identical total trims is a major clue that this is not a bank specific issue.

[@xbin87116]

If the intake is plastic I would smoke it.

[@SchrodingersBox]

I don’t understand that. Why would you smoke it if there is no intake leak?? Where is the evidence of an intake leak?

[@GripFreak]

Matt, you are making this entirely too difficult. Change the plugs and wires. The new plugs and wires are faulty. Oh yeah! Check all the GROUNDS! 🤣🤣🤣

[@SchrodingersBox]

Hahaha and check the battery too lol!!

[@legallass9905]

Pillow thief

[@wayned3137]

The problem is it’s a Ford.

[@SchrodingersBox]

Really? With 336,900 miles on it? What specifically is the issue with Ford? What was the original design flaw that caused this issue?

[@themechanic764]

Vacuum leak

[@MattyEngland]

Unlikely

[@SchrodingersBox]

based on what data?

[@lawnside82]

That crappy plastic intake…

[@SchrodingersBox]

that’s data? plastic intake so you replace gaskets for that reason? I would need something that shows there is a vacuum leak before I did that.

[@themechanic764]

@@SchrodingersBox air-to-fuel ratio vehicle is too lean. To much air so the pcm try’s to match it with more fuel.

[@tomtke7351]

Totally DIFFERENT topic: How to torque... PROPERLY! I once had an FAA certified mechanic explain how to torque and I see several KZbin stars violate these preferred methods. It was explained that like smoothing a sheet on a bed where you start in the middle and smooth outwardly, that torqued surfaces are also torqued starting in the center and working outwardly too. There's another classic pattern found for wheels where the STAR pattern is employed. With this star it is also tighten here and then jump across to opposite side kinda jumping over the center. Then back to this side and back across... CAN SOMEONE WITH DEEP ENGINEERING KNOWLEDGE SHARE H O W T O C O R R E C T L Y T O R Q U E ? P L E A S E 😵‍💫

[@SchrodingersBox]

Yes that’s how I always do it. I “spiral” outward on things like intake manifolds.

[@ACommenterOnYouTube]

if it were lug nuts, start on one lug, then diagonal, then diagonal again like a star pattern until done. If it were a valve cover, or head or intake manifold or exhaust manifold or camshaft, you start in the middle and work out

[@kennykrylov4513]

The irritating part about this video was the socialist Biden ad, I must be bidenophobic

[@SchrodingersBox]

Omg there were biden ads on my channel????? UGH!!!!!!

[@fartblast5058]

Too much talking

[@SchrodingersBox]

And that’s why you are still basic. Load that parts cannon you simpleton!!!