stalling occasionally

signalnc

Original poster
Member
Dec 28, 2012
249
My 2003 TB ext has stalled a few times. Once in park while warming it up in the driveway and once while stopped at a red light. I also notice it starts to "idle down", like it's going to stall, then it recovers. It does this occasionally, not often. I cleaned the throttle body and changed the plugs one month ago--last week of December. I tried to do some research on the web, and when I was on the "old forum" (TV)--my computer got a virus so I stopped searching and decided to post. Thanks.
 

Matt

Member
Dec 2, 2011
4,009
Did you disconnect the battery or remove the fuses for the PCM for 30 minutes when you cleaned the TB?
 

The_Roadie

Lifetime VIP Donor
Member
Nov 19, 2011
9,957
Portland, OR
How many miles, and any other maintenance history or old incidents of the SES light being on?

Some folks report that a clogged/sticky CPAS can cause erratic idle, but the throttle body is certainly the #1 cause. As long as you cleared the PCM's memory as Matt said. And removed the throttle body to clean the BACK. Some people don't read the "how to" article and just spray some cleaner in the front and think they're done.
 

signalnc

Original poster
Member
Dec 28, 2012
249
It has a 440 code for the evap system and that's it..129K miles... I picked up the fuel filler neck line(current one has a leak) but havn't installed it yet. I should get to that Sunday........... and yes I disconnected the battery for at least 30 minutes while cleaning the throttle body. and i also took the throttle body off and cleaned the back side of it..... the truck didn't stall today. We'll see what tomorrow brings.

someone told me that usually when a vehicle stalls like that the ICV (intake control valve--or air intake control valve) will be dirty and not letting enough air in at idle, but i don't think the trailblazer has one. i think it's all part of the throttle body.
 

The_Roadie

Lifetime VIP Donor
Member
Nov 19, 2011
9,957
Portland, OR
signalnc said:
someone told me that usually when a vehicle stalls like that the ICV (intake control valve--or air intake control valve) will be dirty and not letting enough air in at idle, but i don't think the trailblazer has one. i think it's all part of the throttle body.
You have it correct. It's also called an Idle Air Valve on some engines.
 

signalnc

Original poster
Member
Dec 28, 2012
249
So the air must come in on the top front side of the throttle body. I took the little hose off of the brass fitting and shot some carb cleaner in there. Seems to run fine now. maybe there was something in there.
 

signalnc

Original poster
Member
Dec 28, 2012
249
I took off the throttle body again and cleaned it (again-even though it didn't need it) as well as replaced the fuel fill line. The p0440 code came back and the truck stalled again this morning while it was idling in the driveway within 5 minutes of starting.

I did some research and found an old thread about changing the fuel charcoal canister. Someone changed that and it stopped stalling. He never got a code, so my p0440 code may be something separate from the stalling issue.
 

CaptainXL

Member
Dec 4, 2011
2,445
A P0440 means there is a small leak. Try a new gas cap and see if there is any rust on the filler neck. Other than that the system will need to be smoked. So a professional diagnosis is recommended unless you know how to smoke the system yourself.
 

signalnc

Original poster
Member
Dec 28, 2012
249
I already changed the gas cap and the fill line. Still have the 440 code. I have an appointment to drop it off Monday. Thanks for the help.
 

signalnc

Original poster
Member
Dec 28, 2012
249
Took the truck in to the shop. They said it passed the smoke test, so they reset the codes and gave it back to me and said if the code comes back bring it in. Now the code came back on about 4 days after I got it back. P0440. It also stalled out this morning while warming up. It hasn't done that in a few weeks. So my question is if something in the evap is bad, thus throwing the P0440 code, is it possible for it to pass the smoke test? or are they blowing smoke up my @$$?
 

CaptainXL

Member
Dec 4, 2011
2,445
signalnc said:
Took the truck in to the shop. They said it passed the smoke test, so they reset the codes and gave it back to me and said if the code comes back bring it in. Now the code came back on about 4 days after I got it back. P0440. It also stalled out this morning while warming up. It hasn't done that in a few weeks. So my question is if something in the evap is bad, thus throwing the P0440 code, is it possible for it to pass the smoke test? or are they blowing smoke up my @$$?

Yes, it is possible for it to pass the smoke test. What type of shop did you take it too? You need a diagnostics shop familiar with this type of problem. They need to perform a thorough visual inspection and exercise all the components in the EVAP system including testing of the tank pressure sensor and operation of the purge solenoid. My advice is to bring it back (if they are a competent shop) and have them fix it if they are truely concerned and not trying to rip you off. Not sure why they didn't fix it right to begin with. Finding no leaks and just clearing codes is NOT a proper proceedure.
 

AbsoluteZero

Member
Nov 21, 2011
211
Early in my 03's life when the AC was on engine idle would become unstable and fluctuate several hundred rpm's. Don't recall if it actually stalled and I didn't have any DTC's. Still under warranty so had the dealer check on pcm updates. There was one specific for idle stability. Unfortunately the repair order only shows updating pcm with no additional info like a TSB. Try plugging your VIN into this site: TIS and look at the history to see if an update is listed. This info will not tell you if your vehicle actually has the update. This was over 8 yrs old and may not apply but thought I'd mention.
 

signalnc

Original poster
Member
Dec 28, 2012
249
thanks for the replies. I wouldn't say the shop is the most technical savvy shop around. they have been honest to this point. I think they had their best mechanic quit on them the week I had the truck in there. They hired a new guy, I'll go up and talk to him about it.
 

JaySun

Member
Feb 25, 2013
23
Seems very similar to a lot of other threads popping up recently (including mine)

Code:
http://gmtnation.com/f25/whole-car-shakes-idle-need-help-6801/

http://gmtnation.com/f25/another-rough-idle-6760/

http://gmtnation.com/f25/rough-idle-drive-runs-rich-catalyst-p-code-6781/

http://gmtnation.com/f25/idling-rough-lately-6275/

:undecided: subscribed.
 

signalnc

Original poster
Member
Dec 28, 2012
249
I've been doing some research on the p0440 code. I've read about a few fixes, one that came up was a bad fuel tank pressure sensor. Someone posted that their mechanic said the p0440 code was "false" in that usually it is something electrically wrong with the evap system, not an actual leak. I found the part online for about $50. I cannot find out the location of the fuel tank pressure sensor or how to install it. Does anyone know the location of this or how to replace this? thanks
 

MAY03LT

Member
Nov 18, 2011
3,412
Delmarva
signalnc said:
I cannot find out the location of the fuel tank pressure sensor or how to install it. Does anyone know the location of this or how to replace this?

On my 03 it's just to the left of the fill pipe at the rear of the tank.
 

CaptainXL

Member
Dec 4, 2011
2,445
signalnc said:
I've been doing some research on the p0440 code. I've read about a few fixes, one that came up was a bad fuel tank pressure sensor. Someone posted that their mechanic said the p0440 code was "false" in that usually it is something electrically wrong with the evap system, not an actual leak.

Thats correct. Thats why I am stumped as to why the shop you took the vehicle to did not check all the components using a scan tool. Very simple proceedure.

signalnc said:
I found the part online for about $50. I cannot find out the location of the fuel tank pressure sensor or how to install it. Does anyone know the location of this or how to replace this? thanks

It not a good idea to get into the habit of replacing parts like this unless you know they are failed. You can end up spending a lot of money needlessly. Electrical and electro-mechanical parts are usually non returnable.
 

signalnc

Original poster
Member
Dec 28, 2012
249
Thanks MAY03

I was thinking the shop I took it too really had no idea what they were doing captain. I don't think the guy who owns the shop is a mechanic, he just owns the business and has mechanics who work for him. He is honest when it comes to price, but I think his mechanics lack real expertise. they are good at simple things. He seems to have a high turnover rate with employees too. the guy who quit the week my truck was in there seeemd real knowledgable, so I guess i was a week too late. they have a new guy. I'll have to go in and talk to him before I decide to bring it back to them. I know replacing parts seem like a waste of money.
 

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