How to find out why your TrailBlazer Stalls! - Chevy TrailBlazer, TrailBlazer SS and GMC Envoy Forum

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Go Back   Chevy TrailBlazer, TrailBlazer SS and GMC Envoy Forum > 2002 - 2009 TrailBlazer/Envoy Tech > 02-09 Vortec 4.2L I-6 Engine and Drivetrain > OEM Issues

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Old 08-05-2007, 04:27 PM
OneSickS10's Avatar
OneSickS10 OneSickS10 is offline
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2002 Chevy TrailBlazer LTZ
Blue/Pewter 4.2L I6 4X4
Join Date: Oct 2006
Location: Connecticut
Posts: 79
How to find out why your TrailBlazer Stalls!

Check it out guys I believe I have found a sure fire way to find out whether or not your truck is affect by the Hesitation, Stalling and Stumbling issue that is spreading throughout this forum like cancer. I realize you can do it by VIN code, but there are other's who believe they have this problem and are not within the VIN specs so here you go, try it at your own risk, it worked for me now I just need to have the TSB applied to my truck at the dealer this week. First, here is a crash course in EVAP systems for those who are curious, otherwise just scroll down..
(out of Chiltons)

1)The fuel and evaporative emissions control (EVAP) system absorbs fuel vapors from the fuel tank and, during engine operation, releases them into the engine intake system where they mix with the incoming air/fuel mixture. The main components of the evaporative emissions system are the canister (filled with activated charcoal to absorb fuel vapors), the purge valve, the vent valve, the fuel tank pressure sensor, the fuel tank and the vapor and purge lines.
2) After passing through a check valve, fuel tank vapor is carried through the vapor hose to the charcoal canister. The activated charcoal in the canister absorbs and stores the vapors. When a programmed set of conditions are met (engine running, warmed to a pre-set temperature,etc.), the PCM opens the purge valve and the vent valve. Fuel vapors from the canister are then drawn through the purge hose by intake vacuum into the intake manifold and combustion chamber where they are consumed during normal engine operation.
3) The PCM regulates the rate of vapor flow from the canister to the intake manifold by controlling the duty cycle of the EVAP purge valve control solenoid. During cold running conditions and hot start time delay, the PCM does not energize the solenoid. After the engine has warmed up to the correct operating temperature, the PCM purges the vapors into the intake manifold according to the running conditions of the engine. The PCM will cycle (ON then OFF) the purge valve control solenoid about 5 to 10 times per second. The flow rate will be controlled by the pulse width, or length of time, the solenoid is allowed to be energized.
4) The system performs a self-diagnostic check when the engine is started cold. When the programmed conditions are met, the PCM opens the EVAP canister purge valve, leaving the vent valve closed. The action allows the engine to draw a vacuum on the entire EVAP system. Once the proper vacuum level is reached, the PCM closes the purge valve, sealing the system. The PCM then monitors the fuel tank pressure sensor voltage and sets a diagnostic code if a leak is detected.
5) The fuel tank pressure sensor operation is similiar to the MAP sensor. The PCM supplies a 5-volt reference voltage and ground circuit to the sensor. The sensors returns a signal voltage to the PCM which varies according to the air pressure inside the fuel tank. When the air pressure inside the tank is equal to the outside air pressure (as with the fuel filler cap removed), the sensor output voltage is approximately 1.5 volts. With 14 in-Hg vacuum inside the tank the sensor output voltage is 4.5 volts.

So now to make a long story short, the EVAP purge solenoid valve is located on the drivers side of the engine about 3" in front of the starter I can't get a good picture of it but its black, about 4" long and is directly in line with your master cylinder. You can get to it from up top, you will notice it has a red connector on it, I simply unplugged mine to keep the valve from purging to see if my stalling was related the EVAP system and all my symptoms went away. I wouldn't recommend keeping it unplugged, this is simply a way to troubleshoot when you are at your wits end. I haven't had the following TSB done to my truck so I don't want to say go ahead and bring your truck in for THIS particular TSB until I know it works from personal experience. I will in fact bring it there next week so I will update this thread in a few days. But below is the link to the exact TSB you can print out for your records, but don't bring in your truck until I have confirmed that this is in fact the problem!TSB Stalling The reason I say this i sbecause I had a tune done from PCM for less and I am still having this problem. I do NOT believe the most up to date software from GM will get rid of this unless it is specifically addressed. I believe this EVAP setting is a variable that is not touched when the software is updated in the PCM. That is just my 2 cents, otherwise with my new PCM i wouldn't still be having this issue.
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Old 08-05-2007, 05:01 PM
tblazed's Avatar
tblazed tblazed is offline
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2002 Chevy TrailBlazer LS
Summit White 4.2L I6 2WD
Join Date: Sep 2004
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Interesting... I haven't had my '02 stumble as it warmed up (it would drop down to 150-200 rpm) and possibly die (did a few times) from the EVAP issue since I got my PCM back from them almost a year ago now. I asked specifically for a full "Latest GM" reflash first before they applied their tuning so I think I got it.
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Old 07-21-2008, 07:37 PM
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MikeyDizzle MikeyDizzle is offline
2001 Pontiac Formula
Artic White Other 2WD
Join Date: Nov 2007
Location: AZ
Posts: 196
Wow.... I guess this is what is happening to my TB now? Something purged (sounded much like a nitrous system purge) and startled me. I just installed my PCMforLess PCM and this has been happening once every other 3-4 time I start the TB....

Any advice guys? Oh and my CEL is staying on too....
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Old 07-21-2008, 10:27 PM
hoezaycuervo hoezaycuervo is offline
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2002 Chevy TrailBlazer LS
Pewter Metallic 4.2L I6 2WD
Join Date: Aug 2006
Location: Concord, NC
Posts: 31
What is your CEL code? I have P1441 which is EVAP system flow on non-purge, so I'm thinking my purge valve is shot. I am going to replace it and see if that fixes my issue. If your hearing it purge, I'm thinking it might be sticking and building up too much pressure. Get the CEL code read and post it up, they are pretty descriptive for the EVAP system.
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Old 07-22-2008, 03:38 AM
Africandude13's Avatar
Africandude13 Africandude13 is offline
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2004 Chevy TrailBlazer LS
Graystone Metallic 4.2L I6 4X4
Join Date: Apr 2008
Location: Ontario, Ca
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I had mine stall on me twice after i revved it in park,
but since i cleaned my Throttle body its been really smooth and hasnt gone below 500 Rpm
Check out my CarDomain
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Old 10-17-2008, 03:22 PM
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bigbadbowtie088 bigbadbowtie088 is offline
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2005 Chevy TrailBlazer LS
Baja Black 4.2L I6 2WD
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Originally Posted by Valv View Post
Back to the top
Ok.. really why do you keep saying that? This is atleast the second thread that you have posted that in. I understand Bumping a thread to get the thread active again but really back to the top, makes no sense.

My car domain
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Old 10-18-2008, 12:42 PM
darrin419 darrin419 is offline
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2003 Chevy TrailBlazer LS
Midnight Blue Metallic 4.2L I6 AWD
Join Date: Aug 2008
Location: Chicago, IL.
Posts: 10

I thought me stalling was an isolated problem. after reading this thread I see that I'm going to have to research a bit more. over the past summer my TB started to just die when I came to a stop. Sometimes it happend when I turned left and died in turn. I noticed that then I came close to stopping it started to die, but if I kept the RPMs up just a little it prevented it from stalling. I always use 93 octane and had my fuel filters change regularly.

Well the broblem went away, It seems my little TB healed itself! .

Now Im thing of cleaning the TB, I read the article, since whatever I seem to do never really turns out to go smoothly. Just how bad can someone screww up thier truck by messing it up?
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Old 01-18-2009, 03:55 PM
jblarsen jblarsen is offline
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2006 Chevy TrailBlazer LS EXT
Sand Beige Metallic 4.2L I6 4X4
Join Date: Jan 2009
Location: North East Pa
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I have an 06 Trailblazer that runs great in drive until it warms up and i stop at a stop sign or put it in park after its warm, the rpm's die right down, the volts drop down. If I put it in neutral all the gauges go back up, we've replaced the alternator and the battery both, then someone said to clean the throttle body so we did that and it's still acting up can anyone help me out here?
Thanks it only has 45,450 miles.
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Old 05-15-2009, 11:22 AM
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JMalia JMalia is offline
2006 Chevy TrailBlazer LT
Black 4.2L I6 4X4
Join Date: Jul 2006
Location: Monroe, CT
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I also have a PCMfor less reprogrammed computer and now there is no check engine light, but when I run for codes it gives me 0446 which is for the EVAP canister vent solenoid and canister.....
Jay - PCM4Less, Boss 316's

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Old 05-15-2009, 04:16 PM
WOOLUF1952 WOOLUF1952 is offline
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2003 GMC Envoy SLT
Magnetic Red Metallic 4.2L I6 4X4
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Originally Posted by JMalia View Post
I also have a PCMfor less reprogrammed computer and now there is no check engine light, but when I run for codes it gives me 0446 which is for the EVAP canister vent solenoid and canister.....
Did you have your PCM tuned? Or did you get a replacement PCM and not get the C.A.S.E. relearn done?
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