HELP!!! Idle issue/ let me explain...

[m3rob95]

Ok, my roommate recently purchased a 87 325is. After about a month of driving, upon returning to his car and starting it, the idle would go up and down in between .5k and 2.2k. basically revving up on it own to around 2k then dropping back down then returning in a stedy rooom rooooom pattern. He took it to his mechanic and the mechanic said it was the following:
Engine control unit
Idle control valve
Intake air boot?
and the DME....

My question is how can we fix this ourselves, and do yall even think the mechanics diagnosis is even correct? we are both relatively new to e30s and have little mechanical skill, but have a lot of spare time to where we could potentially get it done.

If anyone has any ideas, any at all, PM me! My buddy and I appreciate any help that you all can provide. Thanks.

[NC325iC]

are you ready...


SEARCH

[m3rob95]

do you know yourself? these search engines are a bitch. if you know how about you explain...

[Ant's Bmw]

rob, i had the same problem with my '87 325e. My idle control valve was bad. To be sure you can test the sensor coming of it(atleast on my e30 m3 you can. its been awhile since i looked at the icv on a 325). Im not sure of how many ohms the icv should be at on the 325is but im sure you could find that out through a search. If you're on a tight budget im sure someone on here will have one for you for a good price, but if not you're always better off ordering an oem replacement. Pelicanparts.com is usually pretty good but there are many others. Hope that helps,

anthony

[Court M3]

check all vacumn hoses also

[strad]

And one of the vacuum hoses is the intake air boot running from the MAF to the throttle body. You might have to remove it to fully inspect it from all sides.

I'd try removing the idle valve and cleaning it really well before replacement. Brake parts cleaner or carb cleaner. Make sure it's dry before reinstalling it.

[CarsSuck]

He should really just replace that intake boot, because its probably pretty old anyways and its cheap insurance. There are several vacuum connections at the throttle body that can leak.

The DME is probably fine, just a sly/cocksucking mechanic. But cleaning or maybe replacing the ICV is a good idea.

[tenzokenny]

I had the same problem with my 88 325 so i just replaced my idle control valve and it was gone

[cravnpup]

same as the other idle post. it's either your ICV or a vacuum leak. clean your ICV, inspect your intake elbow and valve cover to tb tube for cracks, and inspect/replace the o-rings on your oil return tube...

[llll1l1ll]

Just tap the ICV while its running and see what the engine does.

[winstontj]

Search under my username. You'll find a ton of threads asking the same questions. Also buy a Haynes, Chilton or Bentely manual, volt meter, torque wrench and a decent set of tools.

If you unplug the ICV the motor should idle at ~2,000rpm. There are two types of ICV's One has two prongs one has three. The manual will tell you what the Ohms and power should be to test them. If it tests OK then look elsewhere. I replaced just about everything I could only to find that I had a loose connection under the intake manifold. I hack-rigged it for short term and now need to go back in and solder and fix.

Check your MAF (CAREFULLY because they are expensive), intake boot, vacuum hoses, oil filler cap, dipstick, brake booster hose, little metal elbows coming out of the TB, etc. Check all air/vacuum fittings, check your TPS and throttle body/throttle plate. Check your cap & rotor, valves, spark plugs, wires, air & fuel filter and all general tune up procedures. Also if you are ambitious ensure that your fuel injector seats are not dried out and leaking. Check your intake gaskets, o2 sensor, cat.converter, etc. Many, many things all go into the ECU to control the car. One loose wire can really screw things up.

It's best to get a manual, search the archives (for more than 3 minutes) and start digging in.

Good luck!

[bumpstop335i]

Clean it first!!! in diesel. give it a soak first for about 30min and give it a scrub with an retired toothbrush.