2005 Trailblazer Stalls 4.2L I6

I am really confused, I have a 2005 trailblazer that sputters and stalls and there are about 5 threads stating different options on how to fix it. So here are the exact details and maybe someone can narrow down what I need to do.

My trailblazer starts fine and drives fine for the first 5 minutes. Then I lose power and the truck sputters and almost stalls. If I come to a stop it actually does stall. When I step on the gas it continues to sputter and I can't get it over 15 mph. The more I step on the gas the higher the RPM's go but no power and the sputtering is still there even at 3-4K rpm. This will occur for the next 10 minutes or so until it gets hot. Then the truck will run fine. I can park the truck for a 1-3 hours and all will be alright but if it sits longer (especially overnight) then the same condition returns. I read that it is the throttle body so I took it out and cleaned it. The Throttle body was blackened with tar like substance but I got it clean as a whistle after using an entire can of cleaner. I disconnected the battery cable overnight and then reconnected it. I turned the key and let it sit (not started) for 5 minutes just like a member here posted and then started the truck and let it idle for 5+ minutes. All seemed OK for about 2 days and then it started again. Still have the same problems. Also tried fuel injector cleaner and premium gas. Also used dry gas in case of water in the tank. Nothing has worked.

The following remedies have been posted on this site but not sure which one to start with next:

Upstream O2 sensor
Downstream O2 sensor
Plugged CAT
Bad Spark Plug
Bad Coil

Anyone know what I should do next?? or what other info you need to help me solve this.



Well-Known Member
As Djthumper said, check the codes. I would also check the coolant temperature sensor and the thermostat to be sure they are reading correctly. Read them through the data function of the scanner.


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+2 --^-- on Getting the Codes vs.Guessing. You also left off two other things from your list that might also explain why the Engine is doing "The HuckleBuck" at idle and Stalling Out: The CPAS (Camshaft Position Actuator Solenoid) (P0014) and the CPS (Camshaft Position Sensor) (P0345, P1345) if those codes happen to come up. Do not arbitrarily change out these two Sensor-Solenoid devices without first confirming the listed Trouble Codes.

The next two images show where the CPS is located at the Front Right of the Block (Small, Yellow Circle) and the CPAS is fitted on the Passenger Upper side of the Engine behind the Power Steering Pump (large Yellow Circle). If your Code Reader discovers a P0014 Code and the Connector to the CPAS (Red Circle) is filled with Motor Oil... There are many Threads/Videos that will show you how to replace that Solenoid with this item:



If needed... you can find BOTH GM ACDelco Quality Items on Amazon. Avoid using Cheap, Off Brand Sensors here:



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The CPAS, historically, has not been known to cause poor idle conditions and stalling but does throw codes if it's misbehaving. We need codes read before anything is suggested.


Well-Known Member
Many strange running and stalling conditions can be caused by a bad fuel pump. It can fail intermittently and then recover, quit completely or even have a low output. My pump would work fine for half an hour, then quit. Then I could restart and run for a few minutes and stall again. Then it would restart with rough running.
Check with a gage on a long hose so you can see from inside the truck if the pressure is low or fluctuates when the engine is sputttering.
I replaced the CPAS when I found oil in the connector, but it was still working fine.


New Member
I do not have an OBD2 scanner but I am looking to buy one. Any suggestions on what to buy? There seems to be many out there. I would prefer to spend less than $50.00 but can go as high as $80.00. What scanner would be best to determine this issue I am having. Thanks and once I get my scanner I will post the codes back here.




Well-Known Member
I have the same problem , I had the P0014 code twice and changed the solenoid , sounded fine with a few starts in the driveway , first drive it stuttered 4 blocks away , I tapped the gas and it came back only to stall instantly. I still have a annoying hum / vibration noise when idling that gets louder when accelerating ( it 100% sounds like an exhaust leak in the cabin , under the car nothing ) , I get parts cheap and was going to do the muffler due to it rusting , and figured id do the cat as well , but I cant find a direct bolt on..... im in ny and the emission sticker says it is California compliant. not really looking to cut and pay someone to weld a generic one in...

and yes , I did the tb clean , took it off and got everything off. it was pretty gummy , worst ive seen in a long time , so im guessing the exhaust must have a lot of crap build up , I have a new resonator on and the tip looks like its 20 yrs old with carbon build up on the edges


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@KEEPZ489 Although this one looks exactly like the one on my 2002 TB... with enough Pictures-Specs to describe its dimensions... the check for the 2005 flavor for your vehicle indicates that it does NOT. Even so... I have found Amazon occasionally wrong on cross matching years, etc... I can't swear that the 2005 In-Pipe CAT to Out-Pipe would work because I don't know if there are any real differences... but since this one DOES look and function to an OEM Standard... it might be worth taking the Part Number and contacting Flowmaster to find out for certain. The Price would make this investigation worth the effort and eliminate the need and extra expense of using a Muffler Installation Shop.


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Well-Known Member
seen that one , it is short body only and not carb compliant..... I think I am going to have to buy a standard ext cat and a carb compliant universal and have it welded in at a shop and take it home and bolt it up... only issue will be if the guy is good enough to keep things straight so bolt flanges line up....

you would think with so many of these trucks on the road they would make carb compliant ones...


Well-Known Member
the cat one of the possible causes the OP mentioned , ive already done a few things and still having the same problem stalling. I was really hoping the solenoid would have fixed the issue as I was stalling for a while and finally threw a code twice.

and im in new York and will need a carb compliant cat


P0014 has nothing to do with the cat. Unless you're getting a cat efficiency code, it is very unlikely the cat would throw any code. The only way to test a cat is with a backpressure test or you're getting an actual code for the cat. Or another way would be to remove the upstream O2 sensor and see if things improve. Vacuum gauge is also useful.

I can't recall any instance of a plugged cat causing stalling. Low power, sluggishness are symptoms. If it starts and drives fine for the first few minutes only, it sounds like it fails when it goes into closed loop and starts using sensor input. I'd be looking at the upstream O2 sensor. Check live data with a scanner or OBD adapter would confirm this. Maybe some other sensor (MAP, MAF) is flaky.

I don't want you replacing a cat and it doesn't fix anything.


I don't know about actual voltages (maybe someone else knows) but you can tell if the upstream O2 sensor is working well when it moves up and down fairly regularly. For the downstream it should be relatively flat. If it moves like the upstream, the cat is toast.

Display the sensors as graphs.


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From 23 Minutes on... The Tech demonstrates how to test the O2 Sensor using external Heat and a DMM ... and what Voltages to look for:


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