Dreaded P0300! We know what it's NOT! 2005 6.0 5.3 Lq4 P0455

[@deangaryjames]

Found this really interesting, i'm retired now, but when i'd spent time diagnosing an electrical fault, i would take home the wiring diagrams and study the crap out of it, i mostly worked on brand new vehicles so it had to be an assembly thing, sometimes a French person would put a screw thru the harness , or bolt the harness between the hinge and body, so satisfying once we track it down! But i'm retired now, so i cease to give a damn! I watch you doing my old job instead. Keep it up!

[@daniellaughlin9726]

I get much more out of a diag. videos than just turning wrench videos. Thank you for all your hard work.

[@GARDENER42]

Aye, the diagnoses are the most engaging parts for me, especially when they're real puzzlers like this one.

[@dawsondetrana5496]

I agree

[@theronwolf3296]

I agree. The value of these videos is that share thought process as opposed to 'how to do it'. I learn a lot even when the vehicles are quite different from mine.

[@DonsJunkmail-vg1wt]

I think being all day long on the 'tire machine' is the Real "go to" video 🤗

[@furdbarful]

​@@theronwolf32963q+

[@Andrew-ep4kw]

2:57 Troy is not afraid of crappy tedious work. This guy is a keeper.

[@carlmaruyama6863]

I think everybody has a better attitude when working in a clean and organized environment. I have noticed since Troy has been working, the shop is organized.

[@forgetfulme1719]

means business slow.

[@DonsJunkmail-vg1wt]

'We don't pay him much"....

[@DonsJunkmail-vg1wt]

Why not weld the ground connections😁 Melt rust and dirt together🎉🎉

[@DonsJunkmail-vg1wt]

So how much more do you pay in taxes for a cleaner gasoline??🤔

[@MonkeyJedi99]

That is an ORGANIZED and detail-oriented customer! So much better than someone who drops off the car and says, "Something's making noise, please fix it." - I don't keep the same level of detail as that vehicle's owner, but I do type up a symptoms list and leave a cop on the dash for the mechanic. - One time, on my Saturn, I went DEEP into the woods chasing a lack of low-beams. I spent about four hours with a Haynes manual, matching real wiring to the wiring diagram, doing continuity checks all over the place... It turned out there was a burnt-out connection in the plastic-coated parts of the fuse block. I determined that the low beam circuit could be replaced by the DRL (Daytime Running Lights) circuit. The only reason I handed the job off to a mechanic was a lack of tools. The mechanic actually thanked me for not making him do all the wire chasing, and that I saved a LOT of money doing that myself.

[@weirdwillie]

Ray don't apologize for being on the scan tool most of time. U probably helped a lot of people now and in the future who might run into the same problem with there vehicle. Awesome video.

[@jeffrowlan9877]

when I first turning a wrench a man I worked for gave me the best piece of advice... and that was if you keep going in circles, walk away clear your head! the answer will come to you. even in my later years I be came a construction superintend. and still revert back to that advice

[@devinangola3458]

Not to sure why you’re apologizing for using the scan tool, that was the best part!🙂👍 Your dedication to solving the problem is amazing, trouble shooting in real time! And the wife unit and Troy picking up the slack for you is heart warming.😉 You have a great day Rainman.🙂

[@IR-nq4qv]

Scan tools are necessary for diagnostics, if an apology is warranted, it should come from the repetitive transmission and engine flush / snake oil product infomercials, they get old after the first flush.

[@mod_incllc3235]

@@IR-nq4qv but he always say's "not a sponsor" when using said products.

[@IR-nq4qv]

you don't get to have a legit response to an opinion when you use "always" and "said products" in the same sentence. You must know what products that I'm referring to as I never mentioned the name in my previous post otherwise you wouldn't have coined the phrase ''said products'' .With that.., It seems you're in denial, you dozed off or weren't paying close attention to the BG thumb nails and the hash tag BG product name used in past brake fluid, engine oil, transmission flush / repair videos and video title descriptions. There's nothing worse than someone coming along and trying to steal your eyesight and intelligence at the same time.... I don't care, it's none of my business if Ray uses Crisco or Corn oil, I don't care if he's a sponsor or not, that's his prerogative. Can't a viewer honestly express himself to say he isn't into mundane repetitive flush videos highlighting the same products that look very similar and take on the feel like infomercials? How many flush videos are too many????? You don't have to give up honest opinions to subscribe to channels you like @@mod_incllc3235

[@DonsJunkmail-vg1wt]

​@@IR-nq4qvyeah...there's flushing going even at Mc Donalds.🤧

[@DonsJunkmail-vg1wt]

And how many cereals in the grocery store? Cocoa puffs or frosted Luck Charms.

[@wboyd33]

You go Troy!!! Give those walls hell & make the shop shine like no other person can!!! You're doing an awesome job...please keep it up!

[@throttlebottle5906]

poor fella(real trooper) Troy is. I say move everything 1/3rd of shop over and use pressure washer, after soaking with good degreaser. yes it will make a huge mist cloud and cover everything, so cheap plastic(painters drops) will be great.

[@michaelpressman7203]

And Maya too!🎉

[@dcbacon1]

I really like Troy, he stays humble enough to encourage Ray to teach him all he can, but appears sharp enough to show he appreciates the association. Please stay with Ray for a long time...

[@josepherhardt164]

Actually, in a shop where the boss buys brake clean by the gross, why are you expending this much effort? ;)

[@DonsJunkmail-vg1wt]

Well who cleans the bathroom(s)? Maybe the Snap-on tool guy?

[@ED-ti5tc]

Another reason why i tune in for Ray's repairs! Always learning something!

[@FourSeasonsNorth4x4]

Ray, Eric and Paul…(plus a few others)…not always or necessarily in that order. 😉😁

[@bengt-ericdahl3322]

I agree with You.

[@pjrichie2551]

Almost every time I learn something also! good vid Ray, didn't mind being in the scan tool at all!

[@kassemadam3005]

You act like these scan tool/diag videos are boring but these are exactly what I am looking for. I enjoy the chillax repair videos but I also want to learn more and these videos help a lot. More pls

[@MrCliverlong]

Respect to Troy for digging into the less glamorous job but are so important for a decent working environment. He's a gem.

[@ShayFeral]

I'm commenting about 5 minutes into the video with this comment. I had a similar truck, a 1999 GMC Sierra with the little V8, 4x4. It had the same sound in the drivetrain. While I never actually diagnosed, I've had some people tell me that's in the transfer case; that it's chain driven and has alot of slack in it.

[@KennyBaltz]

Ray, I will bet if that truck had gone into a Chevy dealer for that P 0300 code, they would have changed, plugs, wires, coils, and no telling what else. It would have cost $2 to $3,000. He would have gotten it back with the miss still there and some crazy reason for the miss. Great job Ray. You looked at all the data and went after the one thing that was very slightly askew. That truck is very lucky to have rolled into your shop for repairs! You keep wrenching and we will keep watching! ❤ -KB Chesterfield VA.

[@Doorhandletmr]

Usually what I've came across is pressure cleaning injectors for po 300 but I'm in a colder climate area. Lean codes for the platinum melting. Any mass air problem I came across would stumble on acceleration. I was able to clean them usually and they failed because of cheap after market air filters. Don't know what chevy dealership throw parts at vehicles but that didn't happen at our facility. Retired from it awhile ago don't miss the flat rate warranty.

[@williamdawson3353]

This is how we know you guys have a wonderful marriage. Getting under a running truck while your spouse is switching between forward and reverse is just awesome.

[@mikeyhau]

Not that I don't trust your wife, but I'd chock the wheels. Belt and braces save lives.

[@quietsignal]

He doesn’t have any life insurance😂😂😂

[@louietramposch4559]

Wife unit 👽🤓🎬

[@maxwellsilver3115]

But she knew there was a camera rolling 🤨

[@randyorsini2062]

Notice how many times he told her to put it in park 😂 what you say honey 😮

[@Little_Turdle]

As a rookie diy mechanic with a new project truck, this was immensely helpful. So long as you’re thinking out loud and explaining what is good and not good on the scanner tool, it’s incredibly useful. Thank you!

[@edwardcarberry1095]

Ray, your very good at what you do! Please don't change. We watch you because of that!

[@albertjohnson8108]

I get the videos with scan tools may not be the greatest for everyone. But it definetly lets any of us take the opportunity of seeing how you use the scan tool as an actual tool to eliminate and potentially solve problems! Great video. Helps me and everyone else see how to surf on a scanning device rather than getting lost in the numbers.

[@donalddrake6512]

Amazes me how just a simple replace on the mass airflow sensor can have such an effect on an engine. I felt your frustration Ray and your elation at the end. That's what I love about your videos.

[@bearpuf]

Hi Ray. This video was completely mesmerizing to me for you rethinking what the cylinder misfiring issue was everytime you went through a procedure and it failied. Finding it to be a faulty MAF sensor surprised me as well. One of the many things that makes your channel special is that you make the continual effort to share the dead ends to solving a problem and when you make a mistake on your end you don't delete it. I admire you for that, and as I've mentioned before, it builds my own confidence as I'm sure it does for others. Thanks for the terrific ride today.

[@charlesschneiter]

To come back to your aviation content 😉: It's very, very rare that heat is affecting landing performance to such an extent that operations are not possible. It's the take off performance that suffers with heat - and greatly so. Hot air being less dense than colder air does markedly affect aerodynamic efficiency and engine power output to a point where either the payload has to be reduced or the departure time has to be shifted to a cooler time of day. Ahhh... the 757! What a magnificent machine this was. One of Boeing's finest IMHO! And what a magnificent youtube channel of yours this is - I greatly enjoy each and every minute of it! Greets from an old retired Boeing driver car enthusiast and DIY mechanic ...

[@Conservativetruckeraz]

The amount of integrity you have makes you one of the best mechanics out there. I'm sure most big shops would have just said to replace the coils you actually take the time to fully check and make sure what needs done.

[@CameronDC-Grimes]

Most shops have a 25min Diag limit. Then they ask if customer wants to pay for Diag, most don't because they charge $130-$150 for just looking at it. Then the bill is usually above $800. They only give the master technician 20% of the customer cost. Shop takes in 60-70% If they say yes charge me $800+ then they allow 2hrs. Which is what Ray did at the start without the charge. A professional master tech with extensive electrical knowledge would have done the following: Logical Diag Procedure for Misfireing Cylinders: 1. Mode 3 = Check DTCs take a snapshot or jot down, dont clear them! 2. Mode 7 = Check Pending Codes, snapshot don't clear anything! 3. Mode 10 = permanent codes. 4. Mode 2 = Check Freeze frame data. Freeze Frame Data is the operating conditions recorded at the exact time the ECM lit the MIL check engine light. 5. Research procedures of changing electric components and integral parts. There can be specific order and requirements. 6. Read TSB's related to coils, injectors, plugs, engine compression, ECM. Replace or update the TSB component. • Notify your client of any TSB's and explain the potential dangers of not fixing the issue, possible cost of repairs. If the customer accepts cost of repairs, perform all repairs in a timely manner that matches with book and service protocol by repair manual. • If none of that worked you use a oscilloscope with low amp clamp probe after checking all wiring diagrams, hook up to ignition coils and fuel injectors usually from fuse relay, one usually powers the coils separately and another powers injectors. The coils should show a burst, collapse and secondary jump and oscillation after the primary winding collapse charges the secondary winding in coils, it will match timing with injectors amp and voltage surge/drop and collapse in the same millisecond timeframe

[@lupinesithlord1693]

Wish you were In The cleveland area

[@CameronDC-Grimes]

@@lupinesithlord1693 get a digital multimeter $15, Digital DC Clamp Meter that measures low Amp in mA it just clamps around a wire and measures amperage in that circuit like fuel injectors. Those can be as cheap as $50. A compression test kit is just $30 and it has a rubber side that you put in place of a spark plug and it measures cylinder compression, you do each cylinder while cranking engine, make sure all of them are 20psi from each other let's say all are 110psi and one is 170psi that's over 20% , there are tutorials for compression test on KZbin. Testing fuel injectors is done with oscilloscope and low amp clamp with a back probe (a pin that connects on multimeter leads that you insert into the connector pin of the power wire for injectors. Scopes read in hundreds thousandths milliseconds while multimeters only read 500ms so multimeters can fail to detect some misfire problems in injectors and coils. Look up wiring diagram for your year, make, model on the ignition coils and injectors. 4 pillars of engine problems (misfires as well): 1. Engine Mechanical Condition = specifically the engines ability to compress the air charge and seal the combustion chamber. 2. Engines ability to breath AKA Volumetric Efficiency: this encompasses any condition that prevents air getting in and out of the cylinders. 3. Ignition = Ignition coils and Plugs. Covers everything about delivering a strong spark at the right time. 4. Fuel = this cover's not only fuel delivery but proper fuel mixture. Delivered cleanly and at the right time through injectors and into the combustion chambers at the right spray speed and pressure. These are the tests needed: • Swap Coils, check spark plugs visually. • Do cylinder compression test, anyone can do this if you can remove spark plugs, look up a engine firing sequence diagram on Google, it will show the engine orientation and which spark plug is which # cylinder. This will help you identify which cylinder is misfiring and what plug needs to be replaced and what coil to swap and what cylinder to watch for on compression test. • VE test(volumetric efficiency test) for engine breathing. • Spark plug tester. • 14.7:1 ratio of Air:Fuel test, check MAP, MAF sensor and O2 sensor with fuel trim long term vs short term on scan tool. • low pressure guage for fuel injectors • injector balance test or look at fuel trims "injector test"

[@neilmurphy845]

​​@@CameronDC-GrimesThat sounds like exactly what Ivan would do and him and Eric are very good at finding the problem.

[@calvinevans8305]

34:39 you got me pulling my hair out. Lolol I'm glad you went back to clean the rust off of the frame.

[@charlessmarr7107]

Since I am mostly an old school mechanic these trips into the controls, inputs and outputs of the Great Black Box are very enlightening to me. Especially your unique ability to translate the data into real world observations.

[@marksternall4680]

Great instruction video on the steps in troubleshooting a P0300 random misfires, using your knowledge and common sense. Also how to properly use the scan tool in troubleshooting. I learned a lot.

[@danielweilert]

Troubleshooting is an art form in and of itself. If you have to eventually fire the parts cannon it helps to know which way to point the cannon. Kudos Ray!!!

[@ChristopherEisele]

When it is the right part, it isn't trally the parts cannon.

[@jimsix9929]

yea the airflow sensors on gm trucks can give you misfire codes or lean mixture codes, cleaning them will help some but I only use that to diagnose that that is the problem, you did the right thing by replacing it

[@pud469]

A toothbrush with some spray works really well for throttle body cleaning. The stiffer the bristle the better, but i typically use which tooth brush needs to be replaced first at home.

[@samueljames9342]

I'm glad you remembered to clean that frame surface, my OCD was getting the best of me

[@LilYeshua]

Back in the late seventies and early eighties at my service station job,part of my boss's customer base were little elderly widows who had primo examples of sixties cars that had extremely low mileage and parked under their car ports meaning that they looked practically new. It was my turn to run the station as I and my boss would take turns working every other Sunday,we had one of these widows cars in the work bay for service. It was summer and hot so I started it's engine, raised the hood,put a shop fan in front of the radiator,and turned on the AC. So,in between customers I would get in the car and enjoyed the 23 degree Fahrenheit cold air coming out of the dashboard vents. Yeah, you're right,they don't make AC systems like they used to.

[@zekemontgomery6678]

Like hearing the Texas music playing in the background. Keep the wolves away is a great jam.

[@grahamcockerill2406]

It's great to be able to understand how the scan tools operate and to remedy a problem. Thanks Ray. Aussie Graham

[@bootinnj]

This was such a good diag video!!! just did a lower balljoint on a 05 dakota and the guy drilled the bolt after heating it and then giving me no lip to drill into but patience,a 5lb sledge and air hammer,2 drill bits and pb blast later 2hrs of work to save this guy from a 600$ bill and even got the upper done as well for the cost of parts and a hearty handshake. Now ive got a Customer for life! added bonus dude is a gabber so he's telling everyone

[@davidpederson2905]

I really liked the attention given to grounds. So easy to overlook. My standard for parts canon: not really firing the parts cannon until the windshield washer cap has been replaced ... for the second time.

[@larrybe2900]

Unless he did the first ground he showed us off camera or didn't share the work with us he did not do what I feel is an important part. Just deferring to the brain side of the equation grounds does not fully deal with the ground matter. I can think of another variable even if the vehicle starts and that is the strength of the battery.

[@Bellboy40]

@@larrybe2900 He explained later in the video what he did about that first ground he was looking at. He bypassed it with another test wire to a good ground and it didn't fix his problem.

[@jdrs4214]

Great detective work Ray!!!! You found the offending suspect. …and I learned something new today. You never fail to disappoint me when you say “Stay tuned, because this.. is going to be.. a very good video.” Thanks!!!

[@dond.200]

Troy seems to be more comfortable working along side you on the videos. He also seems to help keep your shop more organized.

[@jkillgore8300]

Way to think "outside the box"! Most people would have fired off 8 new coils first. I have had a similar experience, except with oil pressure. My gauge would drop saying I lost oil pressure, replaced the sensor, same thing oil pressure fell out on hard acceleration. Everyone said "oil pump was bad". Something told me it was something else, spread a packing blanket out, drove on it, power braked it and roasted the tires until pressure dropped out. Turned out to be a blocked oil line to the pressure gauge line that finally popped and caused a BIG puddle on the blanket (ruined it as that caught fire at a later date due to use near a plasma torch.... LOL) but it saved me a 2nd tear down on the 429!

[@patrickphelan3676]

Hi Ray, the temperature thing for aircraft has to do with Density Altitude; which directly affects the performance parameters of any aircraft. The higher the temperature, the "thinner" the air or DA. The DA is critical for aircraft during emergencies of reduced power, like an engine failure during take-off. Each aircraft has a specific chart for calculation.

[@ko9446]

And avionics don’t like high heat. Been stuck a few times on the ground with high heat

[@LeverPhile]

"Thinner" air means less lift and the need for faster take off & landing speeds, which means longer runways needed ...

[@michaelszczys8316]

Ray, what really socks is when you find out what is NOT, and that turns out to be everything.

[@jsh6952]

Those GM driveshafts suffer from an oversized bore for the splines, that lets the splines wear out and get sloppy. Eric O just loves redoing grounds, especially on Jeeps and Rams.

[@boblemon2103]

You don’t need to parts cannon the mass airflow, just unplug it and then it uses some default values, probably would have shown no misfires and then you know you need a new one.

[@craigsparton]

It didn't need a new one, this did not fix the vehicle. Notice how he took it on a test drive and warmed it up before checking for misfires again? You'd never do that unless you wanted to skew the results. You'd immediately check it in the same conditions.

[@paulmoffat9306]

I took care of some corroded body grounds as you did here, but I added some copper no-sieze to the joint - seemed to do the job (I had no further issues during the life of the car).

[@RukarioEnterprisesLLC]

Here's a few things to point out. Vehicles way above 2000s (1990s I do think also) have a few extra parts called Crankshaft Position sensor and Camshaft Position Sensor. In my 2011 Sonata, before the Check Engine Light came on, it had a misfire, so we checked it out and it was the Spark Plugs and CPS. A ready-to-fail Crankshaft Position Sensor could be the culprit.

[@wreynolds275]

Wax on, wax off. Sorry Troy, paying your dues sucks, but the experience and knowledge you gain are totally rewarding!

[@matthewsykes4814]

I've been there myself hunting out a fault a long time ago on something a lot more complex. Did the same as you, found out as much as I could that was working properly before spotting something that looked wrong. It was a badly repaired cable in the end. I still remember doubting myself all the time until I got the root cause. Like you I didn't give up. Great work as always Ray. You are a credit to your profession and it's great to see your lot so full of cars waiting to be fixed.

[@Calango741]

Speaking of your "heat and air conditioning tangent", where I am, we use open windows for cooling when it's only a nice cool comfortable 94-95 degrees. It's when it hits 100 that we finally turn on the A/C; and then when it hits 110+ that they start to struggle. That 116 degrees last summer was when it really got uncomfortable.

[@richardaston6361]

I do like the in depth scan tool video's 👍

[@DanoDonelli]

Great job diagnosing the problem. Most techs would have just loaded the parts canon and never known what the actual issue was.

[@johndesaavedra1040]

Being of a similar troubleshooting mindset, I followed your deductive process. This is why I follow your channel. I saw the MAF as the potential object once you deducted every other possible factor affecting misfires. I doubted the MAF it too, but noting was left. Thanks for taking us through this journey. All the best to your family and to your company.

[@i.fishtank]

When you started this video, I thought MAP or MAF, I've had the dreaded P0300 and P0200 on my Peugeot 206 for a good while now, the P0200 was a faulty knock sensor and i've just placed the MAP sensor as the fault..... 2 hours poking and prodding.... try 2 months Ray ! (Amateur DIY mechanic who stripped out the whole throttle body, wiring loom and replaced pretty much everything apart from the Wife Unit)

[@mlg1783]

Oh yeah. It's 105-110 out here in southern Arizona. Just love turning the AC on after work and being blasting in the face with flames for about 4 minutes before it cools off.

[@scottdowney4318]

I would have tried MAF cleaner. The 3 little sensor resistors can get a dirt buildup. I also hate buying parts unless I try everything first. Pretty smart of you to consider the MAF, which does have an effect on misfires. I have even used a light very soft brush on those before which your told not to do as they can break.

[@PhilTheProf]

And we have just witnessed how a diagnostic technician goes about his work. Unlike the main dealership technicians here in Glasgow, Scotland, who wheel out the parts cannon as soon as the car is in the shop.

[@peasmold1234]

That was outstanding work Ray, I've learned so much about using scan tools, (I'm a long retired uk mechanic) never had scanners in my day, a good ear was important then.

[@peasmold1234]

Neither are mine now :)@@peten8767

[@bryandouglas739]

Rainman said South Main are my go to for learning how to diagnose and fix problems. Thanks for what you are doing for people like me who have the mechanical aptitude but too poor for professional help lol😂

[@ahoytheremate1954]

Ray i had 2 air cons in my kenworth road train and 2 compressors because of the heat in the centre of aussie in summer about 50c in summer

[@bloodybones63]

My BMW went into limp mode once. A new Maf was $225. I pulled it, sprayed it with CRC MAF cleaner. It fixed it. I got lucky. That was 9 years ago, still good.

[@mishahendriks3020]

Maybe install some sort of exhaust extraction apparatus/hose so as to prevent (as much as possible) re-grime of the walls? Especially when the car is backed into the shop? Can’t wait to see the shop going to a new level! Good luck! Nice diag, not really a parts canon, as you only fired one shot. Based on diag. 👍🏼

[@bradhaines3142]

not likely to help with doors wide open all day. itd likely be best to make it a yearly holiday project to just do a whole shop pressure washing

[@russellstyles5381]

@@bradhaines3142 This shop is small enough to make this pointless in warm weather, but a good exhaust extraction system might allow heat in winter. Assuming you ever have cold weather there. Hey it does happen, 8 or 9 times a decade.

[@michaelsecord8862]

@2:00 - Aircraft being unable to land/take-off is somewhat common in places like PHX (Phoenix) airport, jet engines aren't designed to work at the temperatures that can be reached with triple digit air temps combined with tarmac temperatures. It is more common this year though due to the heat dome.

[@MarzNet256]

I think cleaning the TB is always an excellent idea before instaliing a new (or cleaned) MAF sensor.

[@hugh007]

My 72 Mercury with the R-12 AC system used to form frost on the dash vents, on the hottest days in Florida. Thanks for all your videos.

[@colestowing8695]

much as i hate the "parts cannon" method, sometimes you gotta go with what experience tells you and take a risk. I might have tried a quick clean of the mass air but "replace with a known good unit" is an option for a reason. I definitely agree with getting the oe part though, cheap parts are f'ing garbage these days (I've gone down some rabbit holes trying to diag problems with brand new parts that are worse than what they replaced-I won't do it anymore)

[@howiej4084]

I agree. There is a time and a place for everything, even the parts cannon. That being said, I kept my old ride. So the parts cannon is really a swaperoo cannon.

[@colestowing8695]

@@howiej4084 good for you, keep that old rig going!

[@Dysl3xicDog]

Old GM injectors. I have this same issue on my 2000 5.3L still poking at things and injectors were highly recommended.

[@bryannikkila9751]

Good morning from Higgins lake Michigan

[@theronwolf3296]

When ever I'm working on electrical connections (especially grounds on rusty areas) I a good dose of electricians anti-oxidation paste.

[@dowh9577]

As someone who is trying to master my own prosumer scan tool, I get a lot out of observing how you collect and interpret the data it provides. Your analysis gives me ideas, even though the UI is different.

[@Pointlesschan]

Do you watch south main auto? His use of the scan tool is great also

[@mariosolano6631]

Thank you Ray for this video, I am currently doing a diag on a Ford Taurus. Your detailed process helped me narrow down the issue. A faulty MaP sensor and rusty ground. Tahnk you!!!

[@Estranged180]

Nice catch, Ray. It's funny how a minor fault in the mass airflow can affect fuel trim so minorly, that it causes major malfunctions that throw people into a spiral of what's not wrong with it. It's also funny that when that minor fault is not quite identified, but shot down with a parts cannon that rectifies the rest. Then there's the feeling that you threatened the engine with an airgun over a P0300.

[@roxanneabbott8424]

So crossing eyes and dotting t,s huh?? Wait what?? Love the ending Ray, great cliff hanger throughout!!

[@robertsensabaugh5785]

Ray, thanks for showing us that misfires don't always have to do with ignition parts and that should not just assume that's the problem

[@dback68]

In my opinion, this is why "parts store" error code readings can be somewhat dishonest for the end user. I can guarantee that any major chain store would have sold a whole set of wires, plugs, and coils and the customer would have still been at square one.

[@christophercake7419]

You da man! Great persistence in drilling down to the issue. Your troubleshooting with the scan tool is one of the things I enjoy most about your videos. It highlights your excellent knowledge of the systems, and yes, it was a great video! Enjoy your day!

[@xunheilvsnipezx3324]

Not for nothing but i was having the same issue with my 05 Tahoe 5.3..... The fix new knock sensors and a valley cover. My scan tool registered misfires on my scan tool but disnt feel the enging lug, jump, sputter, no physical indication... So i popped the intake and took a look at the knock sensors.... Rust city, so badly i ordered a new valley cover and gasket to remove the corrosion i couldnt see, once replaced the misfires dissapeared.

[@xunheilvsnipezx3324]

Also not for nothing, i see lots of new parts everywhere on that vehicle, If it isnt US, Canada, or mexico AC delco, or GM original the parts may be broken, new from china.

[@MadmanJimbo]

The correlation issue on the TPS is the accelerator spring tension. The plastic bushings in that module are made oblong by the high spring tension. The tension or “hysteresis” changes through the stroke. That tiny bit of slop is enough to cause a tilt inside the sensor on the tracks. So the voltage differs slightly. This will not cause misfires. But it is the explanation to the TPS track variances when you let up on the pedal. In any case, the ECM has an algorithm that corrects for this issue. Don’t ask me how i know. Lol.

[@tomredmond]

A good diagnostics video is always welcomed here.

[@silicon212]

I had a 2003 GMC Yukon XL Denali last week in the bay, that has the LQ4 and the P0300. Turned out to be a plugged catalytic converter.

[@silicon212]

To elaborate fully, the vehicle came to us running really rough. Cylinders 1 and 7 were generating huge amounts of misfires, usually starting with 1 or 7 when first started up. As the engine ran, I'd start seeing misfires on 3 and sometimes 5 as well. The right bank (2-4-6-8) had 0 misfires, so I realized that the problem was on bank 1. On my first test drive of the car, I never even left our parking lot. Started up decently, with a single cylinder misfire. By the time I got to the road, it was misfiring on 2 (according to scantool), but running so roughly that taking my foot off the accelerator would stall the engine. Fuel trims were nearly perfect, with bank 2 (the non trouble bank) would bias a little lean on the long terms. Moved coils, moved harnesses, ran backpressure test on intake (which passed), then I got stumped as you did. Checked MAF; good. Checked fuel pressure; good. Checked injectors; all good. Checked compression on engine, all at 150PSI +/- 2 PSI. Checked cam/crank correlation, was in spec. Issue was not mechanical. Out of desperation at this point, pulled off bank 1 cat and put my blow gun into it with a shop rag to 'plug' the inlet, forcing air into the cat. Pressed trigger on air gun, shop rag went 'pop' back out of the cat, and some noble glitter came out of the outlet side of the cat. Ordered new cat, installed and problem was completely resolved.

[@davidp7163]

Great video Ray! I really enjoy the head scratchers, sitting here trying to think along with you what it may or may not be. Have to say, didn’t see the MAF being the cause. Great trigger pull. Good Job!

[@raymondniven5281]

As for the clunking noise from the driveshaft, check the rear straps that hold the universal caps in the yoke on the differential. They might be stretched, or loose, causing the caps to rock in the yoke. I ran into that on some Suburbans, before you tear the cover of the differential. And from one Ray to another, have yourself a great day!🇺🇸💪🔧🔧

[@badassbiker1974]

Good day to you, Ray! Don't worry about this being a scan tool video. It's good to see how your mind thinks during the diagnostic process when faced with a more challenging problem. I commend you on this one. You stuck with it, a bit of trial and error, and got to the root issue! Well done! 👍 👍

[@976rick1]

I actually loved the scan tool lessons, it was so interesting how you eliminated all possibilities And found the cause. I wish i lived near by to have my truck worked on by a competent mechanic.

[@johndernberger1961]

Great diagnostic journey! Thx for sharing

[@renaissanceman8564]

Rayipedia ,,,,, Truly the “ Bob Ross “ of automotiveness. Ray Ross,,,another Ray painting a cabin by the lake with a cute little Mass air flow sensor under a tree 🌲 there you go. Thanks Ray Ray !

[@kevincurry4735]

Good day Ray. Thank you for all the videos that you put out. Your diagnostic ability is awesome. You Sir have a great Sunday.

[@Luisgarcia-uz5uk]

Wow Ray..awesome..I work for a transit company as a automotive technician and we had an 2009 Chevy express 6.0 with a similar problem, the difference was our vehicle had a misfire on cylinder 7 everything on that cylinder was thrown at it and still same problem, we decided to send it the Chevy dealer and they couldn’t find problem either, so company decided to get rid of it.. looking back that’s the only thing I didn’t look at ..Stupid MAS ..😢🤦🏻‍♂️ Thank you good learning’s Good Job AGAIN!

[@phillipw2493]

The perils of intermittent problems good job and way to go Ray😊

[@jamesjohnson8824]

This episode reminds me of an encounter with a new Pantera MANY years ago. It was brand new. Only made it about 40 miles from the selling dealer before breaking down. Panteras used a Mustang 351 Cleveland 4 barrel as otherwise used in a Mustang with a manual transmission. That meant it had a dual point distributor. Long story short, I identified SEVEN verifiable issues that could have explained the reason for it not running. First of all was a loose screw for the grounding strap on the breaker plate in the distributor. What I learned early in my auto technician career is that you fix what you find and go from there. The truck you were dealing with in this episode had MANY issues contributing to the way it was running and you saw improvement with each one you identified. But you knew there was more to it.

[@module79l28]

But the million dollar question is: did you tighten the clamps on both sides of the MAF sensor when you finished the job, Ray? Because apparently you went on the test drive with them loose.

[@CH-oi1dz]

I saw that too but he did he like to keep us on your toes

[@joesilverbliss1721]

Me too. He probably checked it later

[@fishflash1]

Just a guess, if they weren't tight, the readings wouldn't look so good.

[@SiblingCreature]

There was a jump cut right before that test drive, which I'm pretty sure is when he recorded that bit at the beginning with the air gun, so I think it's fair to say he tightened the clamps in that short period "when [we] weren't looking" as Ray likes to say. 🙂

[@572Btriode]

Yep, the downstream clip wasn't seen to be tightened and it's really doing my OCD. . . . . . . I would also have binned those Bosch (made in India) plugs, couldn't care if they're new or old, they have a zero reputation in Europe, NGK are the general go-to.

[@creamofbotulismsoup9900]

Experienced the dreaded P0300 code this winter when I traveled up to Montana earlier this year. Only was bad enough on cold starts when it was below freezing to trigger a check engine light. To my surprise fuel system cleaner cleared up the misfires. After about 1/4 of a tank of gas after putting in some cheapo Orielly fuel injector cleaner, it stopped. Car had been sitting for a while prior to the trip, so the gas that was in it probably fouled up the injectors.

[@mtn.homeforge351]

Thank you Ray. I learned something today. Please keep up the great videos.

[@shiroikin]

I dont mind the scan tool data videos, it helps me learn a lot actually

[@cranefly23]

An excellent and fascinating bit of detective work there! Well done, Ray. 👍

[@patrickcayton3072]

That engine block ground is notorious for corroding at the lug. Especially on the 02-06 gm model years. I almost bet if you tug on it, it will pull right out. Mine on an 05 sierra vibrated loose at 65 on the highway. It left me stranded had it towed to my shop, KZbin the symtoms, had it fixed in 15 minutes.

[@darkerbinding6933]

Congrats on being able to avoid that Rusty ground bolt on the engine block!! 🤣

[@timm.909]

This really helped me! Also...I like the way you added music to the fast forwarded test drive. Pretty cool!

[@darrelladams4188]

For trying to clean the shop panels….. try a good degrease ( like restaurant degrease ) or oven cleaner.. YES GLOVES would be a must

[@jsh6952]

Simple Green or Awesome Orange will do the job.

[@OUTLAWBBQ]

ATF will make it shinny. Cleans my tools up to brand new looking.

[@TairnKA]

In this situation, "If all else fails, trust your hunches" and you did, based on your experience and skills you chose wisely and that issue has been resolved. Good work Ray (you should debrief Troy on this resolution?). ;-)

[@billmurray4895]

Ray, have you thought about using dialect grease on these grounds? I use it where corrosion is a concern.

[@wayneessar7489]

Florida dialect is very understandable.

[@ohiowrencher8650]

FWIW the grounds under the drivers seat frame had a TSB ( #04-05-25-002E) for them... but it was related to the EBCM. Cheers!

[@bradhaines3142]

when the boss gets right there next to you and starts cleaning, you know you have a good boss. hope you guys mention how much the cleaning helps so he doesnt get too miserable with the low tier labor

[@gridlore]

Ray appears to be a supportive mentor in every way, so I'm sure Troy is getting positive reinforcement on the drudgery tasks involved with running a shop. It's all training to do things right. He's probably learning to be a service writer off-camera.

[@tucker442]

Hi Ray, Kent Moore makes a tool to fit in those grooves on the spark plug covers to pull them off so you won’t have to use your pliers and distort the round of it a bit. I’m sure by now somebody else makes one also.

[@bradleyrorabaugh7764]

Hey Ray love the videos keep up the work. I had a random misfire that took me a while on a chevy ended up being a intake gaskets. Still finishing the video 😂

[@job38four10]

The way the grounds looked made the most sense to me, but I base that on shipyard welding for 35 years where bad ground can cause problems........

[@michaelanderson8010]

Great video Ray. I enjoyed that, your determination paid off!!👍👍👍

[@kurtisstutzman7056]

Wire nuts and electric tape aren't an approved fix...I like this guy....! He's my new mechanic...!!! Thanks, keep up your awesomeness and go enjoy some nature today... Don't forget to compliment someone today...