Weird Low Idle Issue

4x4 AG · Nov 16, 2025

Yes I have smoke at the return spring as well as the sensors. And maybe the base.

Just wondering if it is common or maybe my problem. I have a vacuum leak somewhere that is causing it to dump more fuel at idle.

Juggernaut · Nov 17, 2025

The throttle body shaft seal is located above the MAP sensor so that leak won’t affect trims like one downstream from the MAP. A base gasket leak certainly will.

To narrow it down, disconnect the HVAC vacuum line, EGR solenoid line, and brake booster line at the manifold and plug them. You get an evap code which you can clear but you’ll be able to focus on the engine itself. You’ll have no power brakes so don’t pack the family in the jeep for church. If it still exhibits the condition, look at the intake bolts particularly around the #6 cylinder. Intake leaks are difficult to smoke unless they are significant and in which case you’d probably have a high idle.

4x4 AG · Nov 17, 2025

Juggernaut said:
The throttle body shaft seal is located above the MAP sensor so that leak won’t affect trims like one downstream from the MAP. A base gasket leak certainly will.

To narrow it down, disconnect the HVAC vacuum line, EGR solenoid line, and brake booster line at the manifold and plug them. You get an evap code which you can clear but you’ll be able to focus on the engine itself. You’ll have no power brakes so don’t pack the family in the jeep for church. If it still exhibits the condition, look at the intake bolts particularly around the #6 cylinder. Intake leaks are difficult to smoke unless they are significant and in which case you’d probably have a high idle.

So the throttle body base gasket was a new fel-pro gasket. then i RTV'd both sides, i know, trying to make sure no leak. but it still looks to leak from there.

Honestly it is hard to tell as it is coming from all around the throttle body. The return spring, out of the relief at the bottom of the TPS sensor, and also looks like back next to the IAC.

Could i use the test you are taking about and smoke it again? I guess the main thing i am looking for is where is the leak coming from that is making the jeep throw more fuel at the idle?

4x4 AG · Nov 18, 2025

Ok. so before i put the jeep back together, so i could move it, i smoked it again.

It pours out of both sides of the butterfly shaft on the throttle body. comes out a little of the breather tube in the valve cover vent, so will likely get that as well.

But looking at my fuel trims from before and thinking it was a vacuum leak, do we think the leak at the butterfly shaft on the throttle body could be the issue? I watched the video posted on one of these threads of how to replace the o-rings. thought about trying that.

What are yalls thoughts?

Search

Search

Weird Low Idle Issue

4x4 AG

Member

Juggernaut

TJ Enthusiast

4x4 AG

Member

4x4 AG

Member

Similar threads