Rough Idle Even After Throttle Body Clean [Archive] - Chevy TrailBlazer, TrailBlazer SS and GMC Envoy Forum

: Rough Idle Even After Throttle Body Clean


robmillar
03-01-2009, 12:32 AM
My '02 Envoy with 90,000 has been running rough in morning and idling rough while in drive and stopped. Had throttle body cleaned and mechanic thought it would do the trick, but still same problem. Is the next step to replace the throttle body itself? Any other ideas to get back to a smooth idle? Thanks for any advice!

Teacher
03-01-2009, 12:59 AM
Next step would be to SeaFoam the intake through the brake vacuum line and maybe some new plugs.

Bthracer21
03-01-2009, 11:14 AM
Checking your spark plugs... Fuel filter... Coil packs... running fuel system cleaner and seafoam...

robmillar
03-01-2009, 11:18 AM
Thanks. Is there an article on how to do the SeaFoam? Mechanic wants $300 to do tuneup, but sounds like major portion of it is new plugs...isn't that simple enough to do myself?

MAY03LT
03-01-2009, 11:51 AM
Had throttle body cleaned and mechanic thought it would do the trick, but still same problem.

was the pcm reset at that time (battery disconnect)?

robmillar
03-01-2009, 11:56 AM
Ok, going to show my ignorance right now...not sure what PCM is but I do think they disconnected battery as my clock was an hour behind. Thinking that the CM in PCM stands for Control Module?? P=position???

JJ
03-01-2009, 12:40 PM
P = Power train

hatchet669
03-01-2009, 12:42 PM
as may has said... the PCM needs to be reset after the cleaning... to do that.. just disconnect th enegative cable on the battery for atleast 30 mins..

sctb
03-01-2009, 12:51 PM
Ok, going to show my ignorance right now...not sure what PCM is but I do think they disconnected battery as my clock was an hour behind. Thinking that the CM in PCM stands for Control Module?? P=position???

Powertrain Control Module...the computer that runs the engine and related systems. It is mounted to the driver's side of the engine, looks like 3 blocks side by side. It is reset when the neg battery cable is disconnected for about 30 mins. It takes a bit of driving around for it to learn your style of driving afterwards.

Bthracer21
03-01-2009, 02:03 PM
Everything that has been mentioned thus far... Is do it yourself jobs. The reset takes 30 min to do... The spark plugs take maybe an hour... Throttle body might as well be cleaned while your doing the plugs since all the air box stuff is off so that another 30 min. So in reality an hour and a half to two hours and you can do a basic tune up. Which I already did my plugs but the way I would do it if I was you...


I would dump the seafoam in the booster...
Wait 10-15 minutes, start it up and get the smoke out...
Disconnect the battery...
Get to work on changing the plugs and cleaning the throttle body... Put everything back together and check connections.
Start her up and see how it runs.

hawkhuff
03-08-2009, 06:30 PM
as may has said... the PCM needs to be reset after the cleaning... to do that.. just disconnect th enegative cable on the battery for atleast 30 mins..

The negative pole? It won't work if you disconnect the + pole?

That could be my problem then.

I changed my plugs today and replaced a faulty coilpak on the #2 cylinder. That was pretty easy except for #1 cylinder. The wire harnes plastic box prevents you from getting the coilpak out to chaneg the plug. Does anyone know how that thing actually comes off? It has two weird looking white clips that appear as though they won't come off without breaking them.

I also cleaned the throttle plate but I used carb cleaner and it appears it cleaned it up just fine.

Got it all back together and it is now running rough and the service engine light is blinking on and off then goes off for a bit then comes on again doing the same thing.

Anyone have suggestions what to do next? :suicide:

ty949
01-10-2011, 04:35 PM
Just got mine back together after cleaning throttle body, still runs rough and service engine light is on???? HELP!!!

the roadie
01-10-2011, 04:54 PM
Need the code. Can't do a thing about a SES light without the code.

And you have to drive around a bit (hour or two) after the cleaning to get the computer to relearn how the system works again.

And describe the roughness. Erratic idle like it goes up and down you can see on the tach? Or a higher frequency (10 Hz) rumble that's worse in drive than in neutral?

bromanjr
01-10-2011, 05:15 PM
hawkhuffI also cleaned the throttle plate but I used carb cleaner and it appears it cleaned it up just fine.


ty949Just got mine back together after cleaning throttle body, still runs rough

Just a sanity check, did either of you guys remove the throttle body to clean the backside (the backside is where all the sludge accumulates)

If yes, then, like it's been said here, get actual Codes from the truck to troubleshoot further.


And, no it does not really matter which cable you disconnect, but the Electronics Gods will be happier if you disconnect the Negative cable for a reset of the PCM.