Idling at 3,000 rpms

[davejake]

You may have seen my pictures... I picked up another '81 1500 X this weekend (from our fellow member Bob Rine). It hadn't been started in a couple years, so once I got new gas flowing through it, we eventually got it running!

Now, I need some advice!!!

When it first starts, it idles pretty rough, but holds around 750-1000rpm (with a little help from my foot on the gas). Once it is warm however, it jumps up to 3,000rpms. It's not a stuck cable/throttle issue.

What should I be looking for to resolve this?

 

[lookforjoe]

Assuming it’s EFI, some of the areas that effect idle rpm would be auxiliary air slide (stuck) & connected hose (torn/ruptured), air flap in meter, connecting inlet hose & breather vent pipe, problem with mechanical timing advance (stuck), and air leaks all over (injectors, manifold/plenum, etc)

 

[davejake]

In case you were curious!

 

[ianlawson]

I picked up another '81 1500 X this weekend (from our fellow member Bob Rine).
Wow, nice looking X!! Lucky you! Now look after it, please!

cheers, IanL - NZ

 

[davejake]

OK, I've checked everything I think of. I did a cold start, started nicely, but immediately jumps to 3000rpm idle. I did check the throttle position sensor, it was a little off, such that you couldn't hear the switch click when in idle position. I adjusted, but no luck.

I stuck my finger in the Air Flow meter to check on the door, and while the door was open, I noticed that if I opened it further the idle did drop although it ran very rough.

Where do I look/test next?

 

[kmead]

I would try blocking the auxiliary air valve to see if it is staying open. If it is, then figure out why. It is electrically heated and also heated by the head of the engine. Check that it is getting a full 12v anytime the engine is running.

I would download the Fuel Injection trouble shooting manual in the WIKI and follow that, it usually does the trick. Be methodical.

 

[davejake]

Thanks for all the advice, I think I figured it out! The TPS had been rotated clockwise and was not allowing the throttle to fully close. I loosened, re-adjusted and now it seem good! Sometimes.. it's the simplest thing!!!