Erratic RPM

[Vegas227]

Alright guys,
I have done lots of searching around on the forums about erratic idles and high idles and what not. I was able to calm down my high idle with a new ICV and ICM. But it still has an erratic idle when I give it gas. I have extensively done fuel injector cleaner and fuel system cleaner every time I fill up. And 2 times a month I will sea foam it. So I dont think it has to do with my fuel system. I am thinking it has to do with my distributor cap and rotor. I put in an order to get a replacement from Oreilys which is the only place out here. Also my MPG gauge has been going from functioning and not functioning and I am confused why it keeps going in and out. One day it worked and then it stopped. Now all it does is go from 40-0 and vice versa every time i give it gas and let off the gas. It doesnt stay like it used to at a certain MPG.

So I guess the question I am trying to ask is, what else could be causing my erratic idle when I give it gas? She purrs at 800 rpms until I give her some gas and then it throws the idle off wack.

Thanks,
Andrew

[irish44j]

the first thing to do is IACV delete, and just control throttle at the throttlebody butterfly (via the adjuster screw). Yeah, you have to give it a bit of gas for a few seconds at startup to keep from stalling, but after that the car runs great and idle stays consistent no matter what.

[e30jake]

^this

[Vegas227]

I just spent 300 on a new IACV and now your telling me to take it off? :(

[thebutterson]

I'd lay off on all the cleaners. If you're using good fuel there's no reason to use seafoam twice a month along with extra additives every tank. I remember an e46 thread where I guy went overboard with cleaners and did some damage to his fuel system. I can't remember exactly what went out though, I want to say injectors.

I've heard of "reseting" icv's where you unplug it, hold the rpm where it should be idling at with the throttle, and then plug it back in. It has something to do with centering the range of the ICV. It's free to try, so why not?

[irish44j]

I just spent 300 on a new IACV and now your telling me to take it off? :(

you spent 300 dollars on a new IACV?? :-x

what I'm really telling you, though, is that you can diagnose things easier by removing the IACV (and associated vac tubing, wiring, and idle control module) from the equation.

btw, did you test your old IACV? It's an easy test. Mine tested out fine, but I was never confident that it worked correctly. Also replaced my idle control module (behidn the glove box) which fixed it for a while, but then it went back to bad again. I did all the tricks (washer in the tubing to restrict airflow, etc). No dice. It's just a lousy system.

Anyhow, if you plug the IACV, and plug the hose coming from the elbow, that takes that system out of the equation and will get you a regular idle (using the screw on the TB) and you can narrow anything else down easier.

The IACV system is pretty lousy on these cars anyhow. Since I removed mine I just need to give it a bit of gas for 10 seconds at startup and then the car idles just fine - even on cold mornings.

By deleting, you get rid of several potential trouble spots:
1. the IACV
2. the Idle control module (you don't actually get rid of it, but you unhook it from the IACV)
3. the wiring
4. the vac tubing that's part of the idle system (there are 3 different tubes, and any of them leaking will FUBAR your idle)


The other upside is by using the throttle plate screw, you can set the idle wherever you want. 700rpm, 1000rpm, whatever. And it will actually say there +/- about 100rpm. And you get to pull a bunch of crap out of the engine bay.

\

[Hey_You]

The other upside is by using the throttle plate screw, you can set the idle wherever you want. 700rpm, 1000rpm, whatever. And it will actually say there +/- about 100rpm. And you get to pull a bunch of crap out of the engine bay.

This is what I will be doing. I hate the look of un-needed hoses and such.

[matt0300]

Can someone post a picture of the idle control module?

[Vegas227]

Its a deck of cars in your glovebox. Open your glove box and take off the screws/tab things from the top cover and pull it down or out. It is up at the top, you need to unplug it before you can fully take it out. If its original i think it should be green. I think mine is blue now.

[matt0300]

Ok cool thanks.

[irish44j]

I didn't physically take my idle control module out. I just unhooked the two wires from the IACV, taped them off, and called it a day. Not sure if anything else involved in the idle control valve affects any other aspect of the ECM, etc (there are alot of wires coming out of it), so I just left it because I'm too lazy to investigate the electrical diagram.

It's not heavy or in the way, so I just left it there.