After completing much work on my '95 Jimmy, the idle is fluctuating at start up and continues to idle high even after warm (about 1200-1500 rpm). I've read about a lot of possible causes but I'm wondering if a leaky nut kit could cause this issue? Another reason I suspect a fuel leak is that the fuel pressure measured at the manifold immediately drops to near zero shortly after turning off the key.

I replaced the fuel pressure regulator a while ago and from what I saw, I didn't think the nut kit was leaking. I'll attach a picture below. Wouldn't the driver's side of the plenum be washed if the nut kit was leaking?

Thanks

 

Before doing anything with this,which doesnt sound like to be your problem,id check for vacuum leaks,and check the pintle on the egr. if its stuck open from carbon it'll run high like this. if its dirty,clean with with a toothbrush and brake cleaner.

 

Along with the other things mentioned check the TPS. I was fighting an idle issue that would come/go. Turned out the TPS was just a hair off and would cause the engine to go lean and give the high idle. How that's possible since it has little to no adjustment for installation.

 

I think I'm OK on the egr valve...that was replaced recently and I used a gasket with a screen. I had to pull the old one several times to clean it...very similar symptoms but always triggered a check engine light. I'll keep it in mind though.....right now, I'm hoping for a vacuum leak.

I'll also check the TPS...I'd at least like to make sure it's getting the proper voltage.

Thanks guys.

 

High idle is definatly vacuum leak or tps problem. Leaking fuel will cause it to bog down and be more of a low idle and wanting to die. You picture looks like classic fpr fail. I do notice some clean area around the poppets for cyl 3 and 5. They rub on the fuel lines right there, may want to check that out after the high idle is corected and problems persist. But fuel leaks dont casue high idle. Might sound stupid but did you make sure the booster vac line and the other one on the back are plugged in good? Also there is a splitter on the smaller line that other lines can slide off, happened on mine when i remove the upper intake.

 

I only had a few minutes to look today but the lines all appear to be connected. Here's the kicker....the idle was perfect today. It was about 50 deg today and it seems to idle high only when it's cold out. Could that point to the air temp sensor in the air intake?

 

Oh, and at least one vac line was crushed under vac but didn't appear to be leaking...don't think that would affect the engine?? Should that line be replaced?

 

I would suggest finding a vacuum gauge, Also if you have access to a multimeter you could test both temp sensors to determine if they are good. Check your throttle linkage, tge cruise control cable has a sleeve near the throttle blade that needs to be snapped in place that can cause problems. Double check nothing else is hanging up the throttle.

 

You can check those things but just out of curiosity loosen the TPS, turn it as far clockwise as you can and tighten it down while keeping clockwise pressure on it.