Rough Idle

LAMBAS_2000

MEMBER
2008 GMC ACADIA
3.6L
6 CYL
2WD
AUTOMATIC
126,500 MILES

I recently replaced my spark plugs and changed my oil and filter. Immediately following with 1st start up, engine started rough, but immediately smoothed out. Within 1/4 mile of driving, the traction control shut off and read service traction control, service stabilitrack. Within the next 1/4 mile I stopped at a stop sign and the Check Engine Light (CEL) came on. OnStar gave the following codes P03000, P0171, P0174, multiple engine misfires, and (obviously) traction control malfunction. It seems to run down the road fine, but when stopped or in park the vehicle idles very roughly up and down, almost to the point at times of near stalling and almost chugging. Next, I replaced all 6 coils, after which I unhooked the battery to clear out the CEL codes. I have only driven about 10-15 miles since the coil replacement, but the CEL has not yet come back on, but the vehicle continues to run just as rough as before and the traction control system continues to shut itself off and on and give the service traction control, service stabilitrack messages. What is my next option?

4 Replies

HMAC300

MECHANIC
48,601 POSTS

Check your battery for condition including load test if weak it will set false codes. Were the plugs installed correctly and gapped? There may be junk in them. Make sure all duct work going to throttle plate was /is installed correctly especially after the maf and check for any vacuum hose off/cracked/broken. If it ran ok prior to doing what you did then it has to be something that you have done.

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Saturday, February 22nd, 2014 AT 11:32 AM

SIMPLY_ME777

MEMBER
3 POSTS

Hello. I had the exact same problem about a year ago. After looking for about two hours, I cam across a vacuum line that I had accidentally removed with my forearm. You may have done the same thing as you reached for the rear left spark plug (looking at the engine from the front of the vehicle) with the cover removed (plastic) and along the path of that spark plug, there is a vacuum line that has a rubber cap. It simply slips on and off. Well it was torn and I helped it slip off. I bought a new one and replaced and instantly the problem was solved.

Try that.

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Thursday, October 13th, 2016 AT 5:49 AM

NOMALUCIA

MEMBER
1 POST

Hey simply-me777 I have the some problem but I can't Figure out where is that cap can you send me a picture or something so I will know where is that I don’t want to take it to the mechanic because I don’t have enough money and I’m a single mom and I really don't no nothing about car I will Really appreciate it thank you

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Thursday, October 19th, 2017 AT 6:20 AM

KEN L

MASTER CERTIFIED MECHANIC
42,883 POSTS

Im not sure if the person will get back to you but here is a guide on how to find vacuum leaks and how to fix a rough idle.

https://www.2carpros.com/articles/how-to-use-an-engine-vacuum-gauge

and

https://www.2carpros.com/articles/engine-vibration-at-idle

Please run some tests and get back to us so we can keep helping you.

Cheers, Ken

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Friday, October 20th, 2017 AT 1:23 PM