MY 2002 YUKON HAS A ROUGH IDLE STARTING AT 10 SECONDS AFTER START OF VEHICLE, WHAT IS THE CAUSE?

  • Tiny
  • Roughidleyukon
  • 2002 GMC Yukon
  • 111,000 miles

I have changed spark plugs and wires myself.
I took Yukon to mechanic and he confirmed my work good.
He tested and it would give a misfire on a certain cylinder than he would reset and do again and it would give a different cylinder as a misfire. He did compression tests and all checked out. He removed the fuel injectors and tested and all were good. He took coils from the side of engine giving misfires and swapped with other side but problem persisted.
Truck runs fine at higher rpm. Only runs rough (misfire) at idle
Any help would be appreciated.

Wednesday, November 2nd, 2011 AT 1:24 AM

21 Answers

  • Tiny
  • Jacobandnickolas
  • Expert
  • 68,310 posts

If the problem stayed in the same cylinders, try switching the fuel injectors to see if that changes anything. If it doesn't check compression in the affected cylinders.

Was this
answer
helpful?
Yes
No
Wednesday, November 2nd, 2011 AT 1:27 AM
  • Tiny
  • Roughidleyukon
  • Member

It did not stay in the same cylinders all the time.
Fuel injectors were tested and checked out OK.
Compression test was done as well and checked out OK.

Was this
answer
helpful?
Yes
No
Wednesday, November 2nd, 2011 AT 1:32 AM
  • Tiny
  • Jacobandnickolas
  • Expert
  • 68,310 posts

If the miss followed the coils, then they are most likely the issue. Sorry, I don't know how I missed that.

Was this
answer
helpful?
Yes
No
Wednesday, November 2nd, 2011 AT 1:34 AM
  • Tiny
  • Roughidleyukon
  • Member

It did not follow the coils exactly. It was quite random.
Mechanic says spark plugs, wires, coils and injectors were good.

Was this
answer
helpful?
Yes
No
Wednesday, November 2nd, 2011 AT 1:38 AM
  • Tiny
  • Jacobandnickolas
  • Expert
  • 68,310 posts

If it didn't follow them, it could be from a vacuum leak, low fuel pressure, crank sensor or cam sensor.

Was this
answer
helpful?
Yes
No
Wednesday, November 2nd, 2011 AT 1:40 AM
  • Tiny
  • Roughidleyukon
  • Member

How do you recommend proceeding from here?
Are these small fixes or quite labor intensive?
And thanks for your help so far.

Was this
answer
helpful?
Yes
No
Wednesday, November 2nd, 2011 AT 1:44 AM
  • Tiny
  • Jacobandnickolas
  • Expert
  • 68,310 posts

On our homepage, there is a diy for the vacuum test. As far as the crank sensor, it will require special tools and some labor. Just a thought, make sure the spark you get to the plugs is a hot blue spark. Also, on the homepage under diy are the directions for checking fuel pump pressure. There is also a video to help.

Was this
answer
helpful?
Yes
No
Wednesday, November 2nd, 2011 AT 1:58 AM
  • Tiny
  • Roughidleyukon
  • Member

Thanks a lot.
I will give a try and let you know what I find out.
Your insight is greatly appreciated.
Thanks again.

Was this
answer
helpful?
Yes
No
Wednesday, November 2nd, 2011 AT 2:01 AM
  • Tiny
  • Roughidleyukon
  • Member

I spoke to the mechanic today and he did the vacuum test, fuel pressure test and he said he didn't get any codes that would have indicated crank or cam sensors.
The code, I think, he gets is 302? - Misfire on 2, 4 or 6.
It may show misfire on 2, then he would do over and it would then show on 4 or 6. Very random and inconsistent between these three cylinders.

Was this
answer
helpful?
Yes
No
Thursday, November 3rd, 2011 AT 2:51 AM
  • Tiny
  • Jacobandnickolas
  • Expert
  • 68,310 posts

The codes would have been PO302, 304, 306. Did vacuum and fuel pressure check out okay?

Was this
answer
helpful?
Yes
No
Thursday, November 3rd, 2011 AT 2:58 AM

Please login or register to post a reply.

Similar Questions