Idle issues at start up on a 94 Ultra

[Cntrysthbst]

Most of the time when I start the engine the idle goes up to about 1200 rpm and down to about 800 rpm with in a few seconds. This is when the car is warm, if it is a cold start it idles alittle higher and longer. All normal I believe.

Now for the problem.....this happens sometimes, not all the time, and the engine is warm when this happens....after starting it the rpm is at about 500 rpm and slowly goes up to about 800 rpm. Takes about 5 to 10 seconds to reach a smooth idle, but before the smooth idle is reached the idle is rough. Any ideals? Thanks

[Cntrysthbst]

H_lp pl_as_

Yes, I'd like to buy an e......opcorn:

[Ian Szgatti]

I think you could have a vaccum leak somewhere. How does it run aside from the idle problem?

[Cntrysthbst]

At WOT, it hesitates when I first push the throttle. Seems like its ran better before.

[HotZ28]

Usually a vacuum leak will cause a higher than normal idle. Yours is either low idle, or normal idle rpm. This particular problem is very difficult to diagnose without having a live data reading scanner hooked up, when the problem appears. I will assume that you are not touching the throttle while starting.
Now, all we can do is speculate on what could cause such a problem.
1) Sluggish or sticking (dirty) IAC or passage
2) Leaking fuel injectors
3) TPS voltage out of spec @ idle
4) Throttle body needs cleaning
5) Fuel pressure out of spec during starting (not priming to full pressure)
6) Fuel pressure regulator leaking to bypass

As you know, chasing problems by changing parts can be cost prohibitive. Since you never know when the problem will appear, this could take some time to resolve, even if you have a scanner hooked up. Remember, fuel pressure related problems would not be seen on a scanner. If your regulator or injectors are leaking, the two (2) second prime, may not be enough to give full line pressure. With problems shuch as this, most people (including myself) place a fuel pressure gage at the base of the windshield in order to monitor pressure while starting or driving.