Need help fixing my idle air control valve

[cowmoo32]

I just got my 87 325. I haven't had a chance to drive it yet, but my friend said the last time he drove it, the engine would rev, then drop, rev, then drop...

Here's what someone on another forum told me:

The rpm surging is the idle air control valve (can be replaced or removed if you re-route the vacuum lines), easy fix.

I'm wondering if anyone knows how to re-route the vacuum lines so I dont have to buy a new valve. I just need to be able to drive it to where I'm going to work on it (S52 swap in the near future).

[jlevie]

A fluctuating idle can be a sign of a dirty ICV. In which case removing it and cleaning it with carb cleaner until the valve moves freely is the fix. But intake leaks, an aged O2 sensor, or a worn AFM are equally likely causes. Best to find out and fix the real cause than to try to work arund the problem.

[winstontj]

I am having a similar issue. I'll let you know what I find tonight. I agree that its best to keep things as the engineers intended. You want the idle air valve or you might as well tear it all off and put a set of tripple DCOE Webbers on there. I see you live in NC but the car will still run like crap till the thermostat opens even in the summer and winter will be horrible.

clean it out and put it back together. If its busted look in a boneyard or fleabay for a good used unit.

[winstontj]

I took mine apart last night and it was full of crap. The idle smoothed out a TON. Also I messed around with a few of the vacuum connectors and realized that they were really loose. A few zip ties until the new parts get here and a quick clean of the air valve and no more jumpy idle. I'd suggest doing the same.

Good luck

[apexede30]

I have the same problem currently. Also in NC (greensboro).

Brake fluid and choke cleaner the thing. Also, there are 2 different types of valves, from what I understand...Not quite sure how they interact with the engines they WERENT meant to be used in. I'd love a solution, cause cleaning it isn't the solution in my case.

[jlevie]

Also, there are 2 different types of valves, from what I understand...Not quite sure how they interact with the engines they WERENT meant to be used in. I'd love a solution, cause cleaning it isn't the solution in my case.

Have you verified that the valve is actually bad (shorted or open motor coil)? I think your 86 has a descrete idle control module which could be the problem.

[winstontj]

I have the same problem currently. Also in NC (greensboro).

Where in Greensboro? I lived at 3510 Spicebush Trail & on ?? Rock Haven Drive for a little bit... My youngest bro was born down there. That was back when I was a kid.... wow, I guess he's 21 so it was 20+ years ago!!

Anyway, there are two types, The one that's a 90 degree bend is more like a screw solenoid where an internal thing twists to regulate fuel pressure. The other kind is a T which AFAIK is more like a thermostat/plunger rather than a twisting motion. As others suggest I'd try and short it (force it open/closed) and see. Remember warm = closed, cold = open. So it should be open with a cold motor and closed when the motor comes up to temp (when the thermostat opens).

HTH,
TJW

[jlevie]

Actually, the idle control valve is dynamic. Meaning that it's opening changes as necessary to maintain a specific, pre-programmed, rpm.

[winstontj]

OK... so it twists open/closed to allow the right amount of air in? SO how do you jump/hot wire it so it opens/closes for you to check?

I figured out my problem last night... Was driving and heard something that sounded like a turbo... either someone installed a turbo under the hood when I wasn't looking OR i got a vacuum leak somewhere...

[apexede30]

Arrowhead drive, is where I'm at.

Now stick with me guys...hold on..1+1=2.

My idle is fine untill the temperature goes out of the blue part of my temperature gauge and then it does the wierd loping idle thing....this means my idle control is fine? Once the car warms up thats when it goes ballistic.

Comments?...

[winstontj]

Idle needs to be adjusted IMO. (don't forget TPS). Your ICV lets in the correct amount of air to maintain idle when the motor is cold. When the motor comes up to temp (thermostat opens) the ICV closes and the motor relies totally on the TB/Throttle Plate. When this happens it seems that you may have your idle set too low and you get your lumpy idle.

Also could be a fuel or ignition issue. Start with the super easy stuff, cap, rotor, plugs... Then look for vacuum leaks just because it's a good idea - spray starter fluid or carb/choke cleaner on the vacuum lines and look for a change in the idle. Finally look at the TB and open your manual. Put a feeler gauge in there and check to see that the throttle plate is adjusted properly. Adjust and adjust the TPS accordingly.