03 Trailblazer rough idle/hesitation [Archive] - Chevy TrailBlazer, TrailBlazer SS and GMC Envoy Forum

: 03 Trailblazer rough idle/hesitation


skyj
09-21-2013, 07:50 PM
Ok I know this subject is like beating a dead horse but I would like some help with my situation. I have an 03 TB EXT with the 4.2 I6 with 184,000 miles. We have owned this since 110,000 miles and never had any problems with this vehicle until now. When we first bought it we replaced the temp sensor that is prone to failure but other than that just routine maintanance and its always ran fine. About a month ago it started idling rough when we would turn on the A/C, never threw a code. I removed and cleaned the throttle body and since I was in there replace the plugs, I disconnected the battery for a few hours while I performed the work on it. Plugged it all back together and it ran fine no rough idle or hesitation for three days then right back to it again.
The next weekend I ran a half can of sea foam through the intake via brake booster vac line and the rest of the can in the tank, I did not disconnect the battery since I never have had a code this whole time. After the sea foam treatment it ran great no hesitatoin or rough idle then two days later it starts running rough again.
I suspected the upstream 02 sensor so I talk to a buddy who is a GM mechanic at the dealership and he says the 02 can cause those symtoms so while its running unplug the 02 and see if you notice a change. I try this and it still idles rough and hesitates the same, so my question is?? I dont want to start throwing parts at it I really would like to get this right this whole time it hasn't thrown a code.
I dont mind replacing the 02 since its about due.
the things I suspect that I havent replaced:
fuel filter?
upstream 02?
cam acuator?? ( not dirty or oily)
coils??
re-cap runs rough/hesitates, no codes, cleaned TB, new plug, sea foamed, all works for a few days then right back to rough idle heistation.

skyj
09-22-2013, 02:11 AM
Ok it just threw a code PO128 coolamt thermostat is below regulated temperature. Could this be related to my rough idle?? Need a new thermostat??

freddyboy61
09-22-2013, 11:33 AM
What is your temp gauge indicating? Is it below the 210 mark? If you change the thermostat, replace the temp sensor also.

You probably should also check for loose intake manifold bolts, that can cause vacuum leaks.

skyj
09-22-2013, 11:51 AM
What is your temp gauge indicating? Is it below the 210 mark? If you change the thermostat, replace the temp sensor also.

You probably should also check for loose intake manifold bolts, that can cause vacuum leaks.
The temp gauge is below the 210 mark I should probabaly replace the stat anyway, plus that sensor was the one I replaced a fews ago when I bought the vehicle I could see loose manifold bolts causing the rough idle but why would it be fine for a few days then come back it seems if it were loose bolts that it would always run rough. I will check them anyways since thats a free thing to do. Thanks for the info.

wcosh
09-22-2013, 01:18 PM
sounds like you have covered most of the obvious issues that cause rough idle.
I agree that throwing money at the engine is not a good way to solve problems, however
At 184,000 miles you have a lot of possible areas to consider that may be contributing to this.
I am surprized that you dont get a P0300 for the rough idle.
When its idling rough, does it smooth out when you accelerate? or does it miss at higher rpm as well? I would consider the coils may be due for replacement at this mileage. I know they are not cheap.
I replaced all mine at 135,000 KM (84,000 miles) because of one failure and a string of random misfires. That being said I did get codes.
Here is a question for the technical minds on the forum....Does a misfire at idle need to occur multiple start cycles before the computer drops a code?
Maybe you need to live with the rough idle for a few days to see if the compter drops a code and helps with the diagnosis?

Good luck with the issue, you have a frustrating one to solve

skyj
09-22-2013, 01:33 PM
sounds like you have covered most of the obvious issues that cause rough idle.
I agree that throwing money at the engine is not a good way to solve problems, however
At 184,000 miles you have a lot of possible areas to consider that may be contributing to this.
I am surprized that you dont get a P0300 for the rough idle.
When its idling rough, does it smooth out when you accelerate? or does it miss at higher rpm as well? I would consider the coils may be due for replacement at this mileage. I know they are not cheap.
I replaced all mine at 135,000 KM (84,000 miles) because of one failure and a string of random misfires. That being said I did get codes.
Here is a question for the technical minds on the forum....Does a misfire at idle need to occur multiple start cycles before the computer drops a code?
Maybe you need to live with the rough idle for a few days to see if the compter drops a code and helps with the diagnosis?

Good luck with the issue, you have a frustrating one to solve

It really only idles rough with it in gear and the a/c on, it will occasionally idle rough without it on and in nuetral but its rarely/sporatic. it hesistats for a split second when I accelerate but does smooth out at higher rpm. the coils should throw a code if one was bad dont you think? I may try another sea foam on it maybe I just have real bad carbon build up in it I mean 184,000 miles is a lot. It does slightly hesistat at first start up to, like the first two cranks its real slow, but I assume thats because my battery is older than 5 years and is due for replacement. this rough Idle has been going on for about a month now anyway this is why Im pulling my hair out over this a month and no code except for the coolant code.

wcosh
09-23-2013, 12:22 AM
Have you removed the throttle body from the intake manifold and cleaned it off the car?
I dont think you can clean the throttle body completely by running seafoam thru the vacuum hose.
You need to disconnect the battery and take the throttle body right off the engine to clean all the carbon off the back of the butterfly.

Maybe this will help ??

skyj
09-23-2013, 12:31 AM
Have you removed the throttle body from the intake manifold and cleaned it off the car?
I dont think you can clean the throttle body completely by running seafoam thru the vacuum hose.
You need to disconnect the battery and take the throttle body right off the engine to clean all the carbon off the back of the butterfly.

Maybe this will help ??

I explained that in my first post, I removed the throttle body and cleaned it with sensor safe tb cleaner all the while with the batt disconnected. It seemed to work for a few day's then it went back to rough idle, so I ran sea foam through the vac line and in the tank it worked great for a few days then back to rough idle.
Thanks for the suggestion but I already tried all that.

skyj
10-06-2013, 09:38 AM
I figured I would update this. I replaced the thermostat, cleared the code, and replaced the battery which fixed the slow crank, but wife has been driving it over a week now and no codes but its getting worse. While driving now you can feel it hesitating/miss it only seems to happen while under load. If its just idling without a load it will be fine but as soon as you turn on the heat now (we live in Montana heat in the morning a/c in the afternoon) it will be idling at 600rpm then drop to 400. It doesn't drop much and has never stalled but it getting down right irritating and way more frequent I bought an upstream o2 but would hate to put it in if it doesn't solve the problem. I hate throwing parts at a vehicle without a code.

Joel1
10-06-2013, 12:34 PM
Maybe an intermittent failing ignition coil. These are solid state devices not the typical wire wound coil. Solid state can behave pretty strange in failure modes... someone else might have a better idea on how to test but could you pick up 2 coils at a junkyard for $20 and rotate them at each position through your engine to see if it goes away.

skyj
10-10-2013, 12:47 PM
Well its progressively getting worse my wife called and said its violently missing now while driving, still no code. My father-in-law is the sevice manager over at the gmc dealership and I have scheduled an appoitment to get a diagnostic done on it. One of his techs said he sees this all the time with these after the throttle body has been cleaned and the comuter has been cleared it will still try and compensate for the problem and that he will have to do a relearn and reset the parameters blah blah something on it and should take care of the problem. The good thing is since my father-in-law works there I get a family discount and I know the techs real well and will tell me the truth about what is wrong with my rig. I will report back and let everyone know what I find out.

pbagley
10-17-2013, 12:53 AM
You may want to take a look here: http://forums.trailvoy.com/showthread.php?p=1220225#post1220225

Good luck!

skyj
10-17-2013, 01:01 AM
You may want to take a look here: http://forums.trailvoy.com/showthread.php?p=1220225#post1220225

Good luck!

Thanks I will give that a shot. Still no code and the tech who was going to look at it for me fell and broke his wrist so I'm waiting for him to go back to work before I bring it in.

skyj
10-21-2013, 10:42 PM
You may want to take a look here: http://forums.trailvoy.com/showthread.php?p=1220225#post1220225

Good luck!

Well I tried it and still no change. Still no codes I may just break down and take it to the dealership.

skyj
10-28-2013, 05:26 PM
Ok it finally threw a code again then went off again. Checked it with reader and its P0172 system too rich on bank 1. I replaced the plugs when I cleaned the TB. What causes this o2 sensor?? Still is idling rough when it has load and missing while cruising.

drd07
12-02-2013, 10:38 PM
did you ever figure this out? I'm having the exact same problem with my 03 4.2 4x4 envoy

skyj
12-08-2013, 10:41 AM
I think I may have came to a conclusion on this problem.(maybe) May sound weird but I think its my alternator and here is why; we rarely drive this vehicle at night requiring headlights the other night I was driving it at dark with heat on full blast( its been -15 below here) and noticed the voltage gauge fluctuating and the lights diming bad enough to hardly see the road well enough while accelerating then it will settle back down to normal voltage. Now here is my reasoning behind it being the alt, the voltage drop is not allowing enough voltage to power the ignition coils thus allowing a misfire. I may be wrong but I plan to replace the alternator today to test my theory I will report back. If not Im sure its a coil problem and will just do as some have suggested and replace a coil.

jpinoy
12-10-2013, 01:18 AM
I was having a rough idle and getting the P0171 when I first got my 06. Read some of the issues related to that, as I was getting the rough idle/engine shake when idle.

I cleaned the TB... didn't go away. Then read on one thread, that the intake manifold tend to work loose and can throw P0171/P0172 code. I checked them, and they were loose, especially the one close to the firewall. Tightened them all up, yes, they were all a little loose.. cleared my code, and hasn't come back, and rough idle went away. I know yours is P0172, but it wouldn't hurt and quick to check those bolts... just thought I'd throw this out there.

Sent from AutoGuide.com Free App (http://www.autoguide.com/mobile) with autocorrect, typo and all... :D

JwLipsey
12-10-2013, 07:38 AM
@jpinoy: Thanks for sharing that. For several weeks I've been having identical symptoms described by the original poster and haven't discovered the solution yet. Will try torquing the intake manifold bolts this weekend.

@skyj: Perhaps this solution is worth another look, if you dismissed it before. (See also post #4 in this thread.)

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skyj
12-22-2013, 03:37 PM
Well I can finally close this thread with some good news. Yesterday I decided to finally bite the bullet and buy a new coil. I started swapping coils with the new one and no change till I got to #3 instantly the miss went away so I swapped the old #3 back in and the miss retuned so I replaced #3 and all is well again. Whew!! Thanks for all the help and suggestion everyone.

gsxr2k4
01-02-2014, 06:03 AM
Replaced fuel filter, checked all vacuum lines and replaced all spark plugs. Found out where the problem was. Spark plug 2 and 3 weren't making connectivity with the coil pack. So I removed the boot and attached it to the spark plug and there you go. Working fine now.




Ok I know this subject is like beating a dead horse but I would like some help with my situation. I have an 03 TB EXT with the 4.2 I6 with 184,000 miles. We have owned this since 110,000 miles and never had any problems with this vehicle until now. When we first bought it we replaced the temp sensor that is prone to failure but other than that just routine maintanance and its always ran fine. About a month ago it started idling rough when we would turn on the A/C, never threw a code. I removed and cleaned the throttle body and since I was in there replace the plugs, I disconnected the battery for a few hours while I performed the work on it. Plugged it all back together and it ran fine no rough idle or hesitation for three days then right back to it again.
The next weekend I ran a half can of sea foam through the intake via brake booster vac line and the rest of the can in the tank, I did not disconnect the battery since I never have had a code this whole time. After the sea foam treatment it ran great no hesitatoin or rough idle then two days later it starts running rough again.
I suspected the upstream 02 sensor so I talk to a buddy who is a GM mechanic at the dealership and he says the 02 can cause those symtoms so while its running unplug the 02 and see if you notice a change. I try this and it still idles rough and hesitates the same, so my question is?? I dont want to start throwing parts at it I really would like to get this right this whole time it hasn't thrown a code.
I dont mind replacing the 02 since its about due.
the things I suspect that I havent replaced:
fuel filter?
upstream 02?
cam acuator?? ( not dirty or oily)
coils??
re-cap runs rough/hesitates, no codes, cleaned TB, new plug, sea foamed, all works for a few days then right back to rough idle heistation.