Rough Idle or Stalling on a 2002 Trailblazer / Mass Air Flow Sensor Location (MAF)

[@100thomasmagnum]

Completely correct. I have a 2003 GMC Envoy XL (basically a Trailblazer but GMC) and had what began with a rough idle, then stalling from a stop (E.g., at a stop light) that progressed into full stall out. Then I would have to restart and go. Mine was having this issue whether or not I had the AC or heater off or on - did not matter. I took out the throttle body, sprayed throttle body cleaner (only use throttle body cleaner, not any cleaner!), wiped it clean, reinstalled and car now works great! NO more issues. Totally worked. Oddly, the throttle body before clean did not appear that dirty. Its very sensitive so needs to be cleaned periodically.

[@EYVOAuto]

Awesome advice thank you! Unfortunately, It's just gotta be part of regular maintenance with these cars

[@heretohear8662]

Glad to hear your response, as I have a 2005 Buick Ranier (same motor) and it's doing the same thing. I'll give that a try. Thanks!!

[@100thomasmagnum]

@@heretohear8662 yeah totally worked on my Envoy. Problem is Im gonna have to do it every 6 months or so for maintenance to keep the issue from coming up again. But so far still good.

[@shadowopsairman1583]

@@EYVOAuto Ok so what about vehicle sitting idle in park, then suddenly opening throttle and it acts like engine wants to stall? What about rolling and engine wants to act like it wants to stall when steering is turned from stop to stop? Already cleaned TB and did the pcm reset...

[@lingbingchill]

I'm having the same issues with my 02 GMC Envoy XL. Time to look up how to find and clean the throttle body.

[@karguy1720]

Thanks for the info. I had ordered MAF cleaner, and was planning to do my '02 Trailblazer, so this saved me some confusion. FYI, a common cause of rough idle (only in drive) is bad motor mounts. I chased this issue for some time, and finally found many references to the motor mounts. I replaced the mounts last week a solved the problem.

[@EYVOAuto]

Glad this could help, and Thanks for the advice on the motor mounts! Best of luck with your car!

[@DJRIKYP]

yes it is ....its on top of intake behind the throttle body

[@EYVOAuto]

Some of the newer ones do have a MAF. The 02 does not

[@amartinez2071]

MAP

[@DanielRichards644]

That's the MAP (Manifold Absolute Pressure), not MAF.

[@geraldgibson8549]

I have a 2002 Chevy trailblazer First it burns a lot gas what can I do about that also in the morning it will crank but don't start have to turn the key back and forth to the start position three time before it starts

[@EYVOAuto]

I have to say I'm not a certified mechanic so this is just opinion and you'll have to do more research. The ignition switch on these is famous for dying. Your no-start symptom sounds similar & could be related, but usually the vehicle won't crank at all until the key is cycled several times if this is the issue. More likely it's possible you're not getting fuel or spark right away. You may need to use a spark tester to verify spark or crack a fuel line to see if it could be a weak fuel pump or throttle body. It could be something as simple as a crank / cam position sensor, throttle position sensor, or the fuel pump or driver module. (I'm not super familiar with what all this engine is equipped with, but hopefully that gives you a spot to start / think from). As far as fuel economy, it could be possible your vehicle is due for spark-plugs and some basic long-term maintenance. You could try changing the plugs to see their condition. Some people swear to change the coil-packs with the plugs - not a bad idea as the OE ones do like to fail on these. With that you could clean your throttle body and mass air flow sensor (if equipped). Some have a MAF and some don't depending on your model / year - I still don't understand that. And see if your fuel economy improves. These don't get very good to begin with, around 18-19mpg on the highway is probably healthy, unfortunately.

[@fultz.c92]

Your most likely dealing with either bad dirty fuel filter or weak fuel pump next time u drive it cycle key 3-4x before cranking see if it starts right away I work on these nearly everyday.

[@MrZach32]

I’ve done so many things to my 03 trailblazer in an attempt to fix the rough idle. Cleaned the throttle body, replaced ignition coils 4 and 6, replaced the camshaft sensor, the crankshaft sensor, and variable valve timing solenoid. None of these things worked, still have the check engine light on, as well as the issues you described. (Rough idle, stalling, etc.)

[@EYVOAuto]

Shoot, these engine's can be so difficult! Do you know what code it's throwing? In our case, cleaning the throttle body did solve the issue. Depending on how dirty it was, your throttle body may need to be replaced, or it could be another coil pack (We've replaced all the coil packs but one). I don't know too much about these engines, but that's what we've had to do so far. I'm hoping to make another few videos of the car around Christmas when I'm back home and will do some research in the meantime. If you do solve the issue, please leave a comment to let me know what you did, Best of luck!

[@MrZach32]

NDavidson it’s throwing a P1345 camshaft/crankshaft correlation fault. Gonna replace the other ignition coils sometime this week, if that don’t work I’ll replace the throttle body entirely. Hopefully one of these things solves my issue. Thanks for replying!

[@EYVOAuto]

Sounds like you did well replacing the camshaft sensor, but you still get the code? I hope nothing could be wrong with the internals. How many miles did you say you have on it? How did the repairs go? Any luck?

[@wty1313]

@@MrZach32 If you have s p1345 and you have already thrown all those parts at it, your problem is LIKELY a problem with the camshaft phaser or a stretched timing chain. That code only requires the cam and crank timing to be a couple of degrees off to occur. Camshaft phaser is a relatively expensive job requiring getting into the cylinder head cover. Timing chain job, well... Some people opt to just do a whole timing chain job along with the phaser. Note: for what you paid for all those parts, you probably could have paid for a professional mechanic diagnosis - no, I am not a pro mechanic trying to drum up business.

[@ianconley6673]

Check the grounds to the fuel pump or fuel sensor. Has like 3 or 4 grounds to it. They aren't covered so they corrode and can cause this. Just a thought, just watched a video with a guy on this problem

[@jrsears4785]

Soo what do u think bad fuel pump or throttle body needs cleaned...etc

[@EYVOAuto]

Honestly, I would start with the cheapest and try cleaning the throttle body, it probably needs done anyways out of maintenance, and then see if anything changes. If not, I'd recommend taking it to a shop to have the fuel pump tested / issue diagnosed. It's very frustrating these cars break down with such odd issues. We just spent months, lots of mechanic trips and money trying to diagnose and fix a power issue with the windows, locks, and seats on my parents' trailblazer, the most recent problem.

[@KDBRYANT100]

Have had my 02 TB for 20 years. Biggest rough idle remedy was.... MOTOR MOUNTS. Replace maybe 12-15 years ago. Barely tell it’s running at stop No vibrations No mirrors shaking Can of Sea foam every now and then. Coils are super easy to swap out too

[@EYVOAuto]

Great suggestion! That's a great way to make an older car feel much newer. Hope you continue to enjoy your trailblazer!

[@ianconley6673]

The real life peter parker 😂❤

[@jrsears4785]

Yeah mine seems to run great until I start getting between half and a quarter tank of gas then it wants to stall. Plus I was going down an incline the other day and it just stalled out. Just bought it over a month ago I find this car very upsetting. Already put new motor mounts rubber ones . And replace a couple coil packs. Not sure Y it's wants to stall like that!

[@EYVOAuto]

Very interesting, not being a mechanic I can't say for sure, but maybe it's a bad fuel pump? My parents went through a very similar experience when they bought their trailblazer. Lowish miles, really good condition, but then it broke down over and over. They threw in new plugs, coil packs, some wiring, sensors, etc. to get it going again. Cleaning the throttle body seemed to fix the last few stalling issues, but it only ever stalled out on start-up or idle, never under power. To my knowledge the fuel pump hasn't been changed on theirs, but it is a very common Chevy issue. Best of luck! Let us know what you can figure out on it.

[@shadowopsairman1583]

Ok so what about vehicle sitting idle in park, then suddenly opening throttle and it acts like engine wants to stall? What about rolling and engine wants to act like it wants to stall when steering is turned from stop to stop?

[@EYVOAuto]

Anybody have any ideas? I'm not sure, we've been fortunate enough not to have had any engine troubles in the last 12,000 miles after replacing the coil packs and cleaning the throttle body. May just need a tune up?

[@jamesu]

2002 Envoy, in park or gear, slowly tip into throttle and engine dies. No codes, no bad values in data stream. Cleaned throttle body, checked waveform on APP 1 and 2 but were perfect. Turned out to be bad data in the PCM. Disconnected battery for 10 minutes. Problem solved. I have seen this on a few GM vehicles over the years the last one was a 2014 Chevy Sonic.

[@horaciogomez5339]

Wheres the video on fixing the idleing and turning off

[@EYVOAuto]

I don't remember if I did a video on it or not, but if you clean the throttle body it makes a huge difference!

[@randyturner3851]

I have an 2002 trailblazer . It runs for 5 seconds then shuts off . As soon as I push on the gas it dies any ideas?

[@EYVOAuto]

We had that same issue here. I was able to fix it by cleaning the throttle body - which was super dirty - and it seems to have worked, now a year later and no more stalling. I'll do some more research on the issue, but I hope this helps out as a starting point

[@markhayes9114]

I need a scanner like that one

[@EYVOAuto]

It’s super handy and not terribly expensive like some. It’s called OBD Link LX and worth every penny

[@alfredojeri1551]

What is the sensor that is connected on that housing tube that is after the air filter... I have the same issues and can’t seem to find what that sensor is...

[@EYVOAuto]

Hey, sorry for the slow reply! Check this out: kzbin.info/www/bejne/goWaiI2ImqZ6f9E . But I think the one you're referring to is your air temperature sensor.

[@DanielRichards644]

Some 02 model years have a "airflow restriction meter" for lack of a better term that is in the pipe between the air filter box and the resonator box that has the 4200 on it, it just let's you see when you need to replace the air filter

[@amartinez2071]

2006 has one after the air filter.

[@EYVOAuto]

Yes, 06 should have one

[@acmoore7502]

How can I tell if my 03 TB has one or not? The code popped and they surely sold me one but now I'm wondering if that's even an issue. It hit for a couple codes P0172 system too rich P0107 BARO sensor low input P0440 evaporative emission P1514 MAF/MAP sensor

[@EYVOAuto]

If it's throwing a code for the Mass Air Flow sensor there most likely is one. Best way to tell would be to look and see if there is one on the air intake after the filter box leading to the throttle body. Careful not to confuse this with the air intake temperature sensor which is simply screwed into the intake tubing. MAP is manifold absolute pressure sensor and MAF is mass air flow sensor - two very different things in different locations. I'm not a technition but I'm guessing if it's throwing all those codes it's not the MAF but something else. Maybe something with the ECU? Anyone have ideas? Do the codes come back after unplugging the battery for a while to reset things?

[@acmoore7502]

@@EYVOAuto thank you! I have not tried disconnecting the battery yet but I will. It stalled while idling a few times but once I filled the gas tank it seemed to stop. The top of the diagnostic page said "most likely solution is to reprogram Engine Control module" . They said all the codes could be caused by the MAF but now I don't know 🤦🏾‍♀️

[@EYVOAuto]

@@acmoore7502 That is so interesting, does it start hapening again at low fuel levels? If the reset doesn't work you may try replacing the MAF which I imagine is cheaper than a reprogram? Has anyone else experienced these issues and what did you do?

[@Lifegoeson-nv9jv]

Stick with 08-09 TBs

[@EYVOAuto]

Great advice!

[@wyattbohman7112]

Link to the next video? Haha

[@EYVOAuto]

This comment's really old... and I never replied? Haha, thanks for watching anyways! Hope I did more videos on this car... in fact my parents still have it, and it's once again broken down... so maybe we'll do another?

[@bryantnonya8704]

How much did you pay for that car? How much would you have had to pay for an equivalent vehicle? And how much would it cost for you to make that terrible car into a good car? now compare your answers with the price of a quality luxury car and you're probably looking at about the same price... You get what you pay for!

[@EYVOAuto]

Great comment! I’m not sure what they paid for it, but I can say they’ve put plenty of money into it 😭

[@alexschu1245]

Pretty sure this one only has a MAP sensor

[@EYVOAuto]

I believe so, just a Manifold Absolute Pressure sensor. No Mass Air Flow Sensor was added for a few more years

[@notchagrandpa8875]

It does have a MAP sensor and a air temperature valve which can sometimes cause rough idle it's located on the air intake tube just a couple of inches away from the air intake manifold inlet and can be seen in the video it's the small round sensor on the air duct.