Hello.

It seems like I've got a new problem - idle related. I noticed the other day after driving a bit over a 100 miles that my truck had a very high idle. After watching it for a couple days and fiddling with it, it seems most pronounced after the engine has warmed up after driving but still noticeable with a cold start. It is noticeable in all gears. With no load/throttle applied in any gear, the truck is going noticeably faster than normal. I do not have a tachometer.

Couple things:
- Could it be vacuum related? I've been meaning to address my vacuum leaks but just haven't gotten around to it yet. I know I've had some for about a year now. Very distinct hissing sound from the engine.
- My throttle return spring is very funky looking. I haven't messed with it since I got the truck. But it is basically two springs interwoven into one... But it was like that before the idle issue

Any ideas?

Thank you.

 

Might help if we all knew what we are working on. (year, engine, tranny)

 

Right. Sorry about that - 1991 Dodge W150 318 5.2L V8 NP435. Caught me before I could come and edit it!

 

I would check these three possibilities first. Check the injector spray pattern. A bad O2 sensor. A miss adjusted IAC motor.

 

Find\fix the vacuum leak(s) first, reset the codes, drive and recheck for codes.

Did you mess with the IAC or timing settings\adjustment?

 

I will check those things. I haven't messed with the IAC or timings at all. I'm going to address the vacuum leaks as soon as I can and see if that helps. I was thinking about using my neighbor's fog machine (the Halloween style ones) and running some hosing out of the output valve and into the intake tube that normally attaches to the air filter housing.

Will this work? Thanks

 

How is that going to help really...if you hook it to the air cleaner it is only going to get sucked into the t-body but not show any vacuum leaks....a vacuum leak is sucking in air other than into the t-body.

look for obvious cracked and broken lines, use carb cleaner or propane and spray around the throttle body, intake manifold etc to see if the idle changes.

 

Alrighty. I'm going to report back when I'm done. Thanks

 

I'd bet an imaginary dollar your IAC motor is bad. It may still be moving, but not much. This is exactly what happened when mine failed. When you cycle the key, you should hear it moving.

 

Okay. Thanks. I am going to tackle the vacuum leaks first and see where that gets me. Then I'm going to look to the IAC and the things that other have mentioned if that doesn't get me going.