Odd Idle Control Problem

I apologize if this has been covered before, but I've done some searching in other threads to see if anyone has had a similar set of problems related to the idle, but I think mine may be a bit unique. Here are the symptoms:

- Idle will start out fine at around 800 RPM in gear. After a few days, the idle gradually creeps up to 1,000, then 1,200, etc. If I disconnect the battery or remove the ECU fuse from the under-hood box for 30 seconds or so, everything returns to normal and the cycle begins again.

- When having my smog test, the tester couldn't get the engine to hold RPM between 2,000 and 3,000. I tried it myself with the same results. The engine will achieve a RPM in that range, but will mysteriously and instantly drop to 1,000 or so if you try to hold the RPM in that range.

- It also seems to have a slight surge upon throttle tip-in while accelerating from time to time. Nothing big, and not all the time. I noticed it most when I was off-road last weekend.

I've replaced the idle control valve (and cleaned some gunk out of the casting) and replaced the TPS to no avail. Right now I simply remove the ECU fuse every few days that I drive it to keep it happy.

Any thoughts? Thanks in advance for the help.

Fuel filter, clean MAF (check connections), EGR, or maybe fuel pressure switch.

Mine does that rarely. Try spraying off the MAF sensor with a little carb cleaner. If you have an aftermarket K&N type air filter and use too much oil on it.it willstart building up an oily film on the sensor and raise the idle speed.
There are other things it could be as well.
but that is the most common.
Hope this helps.
Andy (Swordy)

Thanks for the tips. I've used MAF cleaner on the MAF once before, but I'll give it another spray. And I'll replace the fuel filter as well.

I'll have to take a loot at the service manual to see where the fuel pressure switch is. The EGR should be easy enough to replace.

An illusive Swordy sighting! Good to see your still lurking around here Andy...hope all has been going well.

Quote:

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Originally Posted by WebbRacing.com

I'll have to take a loot at the service manual to see where the fuel pressure switch is. The EGR should be easy enough to replace.

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Here's a nice writeup:

http://www.vehicross.info/forums/showthread.php?t=12021

Check your OBD codes. Might be 171 or 172, which means common chamber gaskets are cracked. Very common malady.

Thanks for the continuing advice. It's much appreciated!