Experiencing rough idle when I come to stops after driving. On initial start up the idle is normal, but after I drive and come to a stop, the idle is extremely rough. While driving the ride is smooth, nothing noticeably abnormal. There are two things that might have started this, the first one being that the front drive shaft was removed (not anymore) for a little while and the second being that I used Gumout All in One fuel system cleaner. Those things might be directly related or not, I'm not sure it just seemed to happen around the same time.

Around 2 months ago the spark plugs were replaced and had the dealer do a fuel injector cleaning. About 6-8 months ago the MAF sensor, throttle body, and air intake filter were all cleaned. I use "Top Tier" 87 regular gasoline from Costco.

Wanted to get anyone's opinion/experience about what to do to fix the rough idle.

 

Just replaced the MAF sensor and the camshaft actuator solenoid valve. There seems to be some improvement, but the idling is still pretty severe.

 

I read your full thread op. I'm wondering about the cleaning process used for TB?
Did you preform the task?
Did you remove the entire unit and thoroughly clean inside and out with Chem tool or the like?
Did the MAF have MAF spray used to clean it? Did you where latex gloves during the procedure?
Was the PCV hose on top of the engine near the back underside of resonator replaced? They tend to dry rot from heat of engine and age.
Did you check to make sure the intake bolts are all tightened down? They have been known to back out.

Chris

 

MAF replacement oem? We're the screens missing in actuator?

 

Hey Chris,

So the MAF sensor and throttle body were cleaned by me. I used the proper cleaner by CRC. Followed a video on youtube since it was my first time doing so. The entire unit was removed and cleaned thoroughly and I did wear latex gloves. The PCV hose was not replaced, but it seems to be in good condition (not dried out). All bolts were double checked. Today I replaced the MAF sensor with ACDelco 213-1585 and the original camshaft actuator did not have any screens missing and that was replaced with a part directly from GM (12615873).

After resetting the computer (disconnecting negative terminal for ~20min) the idle is definitely improved, but there is still a little rough.

Could it possibly be a bad batch of gasoline? I will put in mid grade or premium when the tank is near empty (currently at 25%).

And should I purchase a new knock sensor, camshaft position sensor, oxygen sensors?

Thanks again

 

Like happy hummer said I would check cam position actuator solenoid for missing screens and oil leaking through connector body into harness connector. Also wanna check misfire counts at idle with a good scan tool, if you have light misfire counts on any cylinder you will then need to check cylinder leakdown. Poor valve to seat seal can cause light misfires with no codes at idle.

 

Checked that an there are no missing screens and the connector doesn't have any oil.

Do you guys recommend a specific scan tool?

Also when I start the car the idle is unnoticeable, but if I shift into R, N, or D (without driving), the rough idle is back.

 

Check this thread if you have not already.

https://www.hummerforums.com/forum/h...what-do-33916/

 

Thanks Doc Old. I'll follow what it says. It does bring up the intake manifold. I don't think anything is loose but I'll check but there is a clicking noise that comes from it, is that normal? And the source of the vibration does seems to be the intake manifold. It vibrates pretty bad and causes the intake to vibrate too.

 

Sounds like a loose manifold; common issue on the I5's.