'05 TB stalling.. someone please help me!!!

I have an '05 trailblazer 4wd Ls 4.2. it's been stalling and idling really rough. Sometimes it will run fine and idle around 900 RPM other times it will mess up everytime i stop. When that happens, my RPM's go down to about 500-600 then when i push the gas it cuts out and almost stalls. it is hesitating bad also... Everything seems to be getting worse everyday. i've had it to 3 chevy dealers and no one can figure out what is going on... I did have a check engine light code PO171 (lean engine) it has been reset, and hasn't came back on YET! I've tried pretty much everything and we are out of ideas.. We've changed the o2 sensor, MAP sensor, intake manifold gasket, cleaned the throttle body,cleaned the MAF sensor, and put fuel injector cleaner in. just yesterday my husband changed the secondary air intake check valve and gasket. We've had the air pump checked also. NOTHING. My mother in law also has a tb and we took our secondary air intake valve off and put it on her tb and her tb started acting like mine so we replaced it. Now mine is doing it again. Can someone please give me some ideas! We have about $600 in it so far (it's not under warranty anymore) all for nothing!!! Any ideas are appreciated!!! :)

Welcome to AF. Many things can cause this and on site diagnosis and testing is the only way, someone has to do a full scan and look at all the sensor inputs, misfire counts, fuel trims and so on to pin this down, there is no quick answer here. BTW you do not have MAF. I would also check fuel pressure, make sure there is a fresh fuel filter on the truck, poor quality or contaminated fuel can cause this also. Routine parts replacement will not usually correct this type of condition as you found out, also check for vacuum leaks. Why was the int. gasket changed, the code indicates a lean mixture which can be fuel related or vacuum related, or at times a bad O2 sensor. Are you saying the condition existed at the time the dealer had the truck and they can't fix it!!??

It is at the dealer AGAIN. A different one this time so hopefully i will get some answers. The int. gasket was replaced because they thought maybe a vacuum leak there. We have checked the fuel pressure and it is good. The filter can't be replaced without replacing the fuel pump which we don't want to do, unless it is for sure the problem as it is $300. We are already $600 in the hole for nothing. The only reason we have replaced these things is because we were told that was possibly the problem since no one can pinpoint the exact problem. Yes the problem has existed when the dealer had the truck and they can't find it. Also i have been told that they can't get it to mess up so they can't figure it out until they see what it is doing. It does it all the time so i don't believe that they can't get it to do it. It is currently at a dealer that hasn't seen it yet so i have my fingers crossed this time!!!! Thanks for the advice though!!!

Ok well i got a call from the dealer yesterday and they said that they couldn't find anything wrong with it except that the computer needed reprogramed. So i told them to go ahead and do it ($200) and i went to pick it up and all was good.... unitl today. i just went to go put some gas in it, and it's doing it again! of course the service dept isn't in today. Anyone have any more ideas?????:banghead:

Yeh, take it back to them and ask them what was 200.00 for it takes 15 minutes to do the updates. Plus I meant to ask you about the $600 spent, if this was the shop's idea, and it did not fix the problem how about a refund. The problem was evident at the dealer, but they couldn't get it to " mess up", doesn't sound right here. Understandably there is an air of desperation here, but if 2 dealers can't pinpoint this problem after 800 of seeming unecessary repairs, sitting at our desks we stand no chance of solving this. Unless the pcm it self is at fault here and they are mssing it, everything I mentioned so far are some of the issues that can cause these symptoms.

Took it back to the dealer today and of course now they are saying that they can't get it to do anything wrong. :banghead: They are saying that nothing is wrong with it. it's been doing this for months and no one can figure it out. So i guess i wasted another $200 on the road to nowhere! :shakehead

PCM reflash / new PCM

at this point, if we were talking about a PC, i would be looking at a hard drive or ram. performance issues and "phantom problems" are caused by corrupt/incorrect system files. since the closest thing to this in a car is the PCM, i would get it replaced. The EPROM inside could be faulty or damaged and could be losing data blocks causing intermittent random problems. If this is the case, then replacing everything in the car will not help. If you want to try this, try the PCM from your mother-in-law's tb on yours. Make sure they are exactly the same vehicle. I believe this will require a secutiry relearn, but should be ok nonetheless. The computer will also pull a CASE error, but you will be ok with this since it is only temporary, when you switch back, all should be fine. It is 7 and 10mm bolts for the PCM then it just comes out of a clip. Install it and see if there is a difference. If you need to do a security relearn, PM me and I can tell you how to do it, or many others on the forum probably could too.

if this turns out to be the problem, then you need a new pcm, or at least get it reprogrammed. There is a webiste called PCMforless.com which is a great tuning webiste, they tune the pcm (yours or theirs) and send it to you. you can either exchange with them or simply get another. cost is about 150. There are even testimonials about them solving problems like these with their services, though you can never trust testimonials...

this is where I would look, but you can also get them on ebay for 50 bucks, be very careful to match the part tho... No telling what it could do if it is from a different vehicle or trans.

Thanks for the advice but i really don't want to spend any more money on "guessing". I have came to the conclusion that i will never have another GM sitting in my driveway! :shakehead i don't know what to do now. We are going on vacation next month and now we don't have a car to take! No one has any ideas, and all the dealership is doing is saying they don't know. I called GM but they don't care. It's not under warranty anymore so it's not their problem. i'm paying $360 a month to look at my trailblazer sit in the driveway! what fun!

Well the dealership said they reprogrammed the PCM. It worked good like i said for not even a day. It's back to doing it again. When i took it in today they acted like i am crazy because they drove it and couldn't get it to do anything. they only thing they saw was the change in RPMs which they said could just be a problem with the cluster... i tired to tell them that i understand that but that doesn't explain the stalling. They don't listen

This happend to a friend of mine. His car started random stalling, tried everything. When I went to check the fuel filter was clogged with rice cake. Someone had put rice cake into the nozzle at the gas station. Had to remove the tank, lines, and injectors and clean them. Car ran fine after that. Be careful when you fuel up, a lot of dipshits in the world.

Just for everyone's info here if the PCM itself is bad it is warranted for at least 7/70 and depending on what state the truck was sold in , my be 8/80.

Wow i didn't know that the pcm had a warranty on it..... how do i find out about the warranty in my state?? I'm in ohio. The dealer did call me today and they said that they still can't get it to act up, so they are going to keep it until tomorrow. I'm really hoping they can get it to act up i can get some answers!

do you have a video camera? bring it with you when you drive, and film it screwing up, then ask them if you are lying...

the videocamera is a good idea but the dealer says they need it to be doing it when they have it so they can scan it to figure out whats going on. I got it back today and it's doing it again so i don't know how they couldn't get it to do it in the 2 days they had it this time. Whatever they did last week when they reprogrammed it worked, but just not for very long! I really wish i could trade it in... I don't know what else to do. They told me to bring it in when it's doing it, and they will scan then but when it does it, it doesn't always do it for a long time. :shakehead

to people more automotively inclined than me: is it possible that the computer they have plugged into the vehicle while driving it is somehow affecting the way the vehicle operates?

Also jpp, are they putting miles on it? I have heard stories about shady dealers saying but not doing what they claim.

The first time they had it, they did put miles on it.. the second time i didnt really think to pay attention. The 2nd time they weren't getting any money for looking at it either since they "fixed" it last time... i had the diagnostics done for free that time. If i take it back, or to someone else i will pay attention! i really think something is wrong with the computer but i can't get anyone to figure it out. The dealer told me to bring it in right away when it's doing it so i have plans on driving around close to the dealer here real soon... hopefully that will work.

Well i got it back from the dealer yesterday.. they put a new pcm in it. All seems good so far... i'm not getting my hopes up yet though. I do have a question about normal rpm's for a tb... what should it idle at (warm)? It's idling around 650, but after all the problems i've had, i had to check it when i got in it, so i put it in park and pushed the gas. It was idling at around 650 and when i pushed the gas it went down to about 500 then back up like it should. It also sounded like it cut out just a little, nothing like before... is this normal?

My will do the same thing, normal, hope you are on track now.

sounds to me like your problem is fixed, mine idles at 600-650 warm so I dont see a problem. congrats and good luck!

Well it's not fixed... my idle is back up to 900 and its hesitating again and my check engine light is on :banghead: Does anyone know if there is anything i can do as far as making GM do something? I've tried calling them, and they gave me a case number and told me they would call me back and never did (imagine that) When i called them back, they "lost" my case number... I contacted a lawyer and i can't get it considered a lemon because it's not under warranty anymore (i didn't buy the extended) and the problems didn't happen when it was under factory warranty. I don't know what else to do, The dealership has guarenteed me 2 times now that it is fixed... obviously it's not. GM made a big deal the first time i called that i only took it to a GM dealership 1 time and acted like it was my fault that it wasn't fixed.. obviously something is wrong, and the GM woodwrench mechanics can't even figure it out! Is there anything i can do, or am i just screwed?

Take it back drop it in their lap and tell them fix it or refund your money as a result of ineffective repairs, your state must have agencys/regulations to handle this type of situation.