Author Topic: Very High Idle - need help!  (Read 64 times)

0 Members and 1 Guest are viewing this topic.

Offline YellowTJ

  • Newbie
  • Posts: 5
  • 2000 Yellow Jeep TJ SE - turbo
Very High Idle - need help!
« on: May 01, 2021, 07:27:17 PM »
Okay, hereís the story. I have a 2000 TJ, 2.5L I4. Was working on putting on a turbo, when I ran into some smoking issues out of the tail pipe. In short, I bypassed the turbo and went back to a stock setup and it persisted. I ended up replacing the head gasket and put everything back together. Everything looked really good within the block. After I got it back together, went to fire it up and immediately started idling very high, around 3,000 rpm.

So started tinkering, checked all the sensors at the intake, and even replaced them actually (Mopar brand). Then checked all the vacuum lines, and replaced anything that even looked questionable. Even pulled the TB and reset a new gasket there. But my problem still persists with a high idle of about 3,000 rpm when I fire it up.

When I do fire it up it does sound like it runs smoothly. So Iím now at a point of not sure what to try next. Any suggestions?!?
« Last Edit: May 01, 2021, 07:33:45 PM by YellowTJ »

Offline Jeffy

  • Administrator
  • Member
  • *****
  • Posts: 14919
Re: Very High Idle - need help!
« Reply #1 on: May 02, 2021, 05:53:11 PM »
I'm gonna guess a vacuum leak somewhere on the intake.
Youtube Channel: https://www.youtube.com/channel/UCZNlr60GXH5OlKIFrT7P6mg
My Jeep: http://4bangerjp.com/forums/index.php?topic=2783.0
"If the motor car were invented today, there is absolutely no way that any government in the world would let normal members of the public drive one."

Offline 95 Lowbuck

  • Member
  • Posts: 139
Re: Very High Idle - need help!
« Reply #2 on: May 06, 2021, 05:10:28 AM »
Maybe the idle air valve?
Unplug it see if it makes a difference.
May sound obvious, but is the butterfly closed completely?
« Last Edit: May 06, 2021, 05:14:15 AM by 95 Lowbuck »
1995 YJ RioGrand, 2.5, AX5, 231 T.C., A.A. SYE,
D30, XJ D44, Truetracs F+R, CV D.S. F+R, 4.88's
R.E. 4" STD., 33-10.50 BFG KO2's on stock rims.

Offline YellowTJ

  • Newbie
  • Posts: 5
  • 2000 Yellow Jeep TJ SE - turbo
Re: Very High Idle - need help!
« Reply #3 on: January 26, 2023, 06:31:33 PM »
Long time since this post, but wanted to follow up with the result. Did a smoke test to learn there was a leak at the intake manifold. This was due to the larger flange on the new exhaust header, and since it shares the bolts to cinch down to the head, the slightly thicker flange wasnít allowing a tight enough seal at the intake manifold, hence the leak. Machined the face of the flange on the exhaust header down, which helped, but ultimately had to machine the upper face at the bolt locations to get it exactly right. Right connection, new gasket, no problems.

Lesson learned, even though it seemed tight and snug, this precision was down to .001Ē tolerance to really get it right. Thanks everyone for the input.

Offline Jeffy

  • Administrator
  • Member
  • *****
  • Posts: 14919
Re: Very High Idle - need help!
« Reply #4 on: January 30, 2023, 12:38:44 PM »
Nice!  Yeah, the flanges can be a place for leaks.  Some of them can be thicker causing problems.
Youtube Channel: https://www.youtube.com/channel/UCZNlr60GXH5OlKIFrT7P6mg
My Jeep: http://4bangerjp.com/forums/index.php?topic=2783.0
"If the motor car were invented today, there is absolutely no way that any government in the world would let normal members of the public drive one."