High idle on my 1987 E30, what should I be looking at?

[Keven]

I just inherited a 87 E30, I got it to run but the idle is pretty high (tach is broken but I would guess around 3000 rpms). What could I look at to fix this problem?

[Holland]

Couldn't tell you, I have an M10 as well, and all I have is a bit of a rough idle.

[Danny]

Vacuum leaks?

[kenika65]

ICV adjusted yet?

[Jean]

Your 87 came with an m10?

High idle could be caused by many things:

bad/stuck icv, vacuum leaks (hoses, gaskets, o-rings), bad icv module, even ecu, engine temp sensor.

Was AFM / throttle cable maybe adjusted to result a high idle? Could be that too.

Start checking the basics.

[Keven]

How do I check the ICV? And actually its an 84, and im a noob at these cars so excuse me if I picked the wrong subforum. Mods please move!

[Hick]

penny!

try cleaning the ICV. to test, locate the ICV [round, pass side over the valve cover]


Unplug it, if the idle dosent change its bad, if it changes but not much, then the ICV needs cleaned. Get some brake fluid cleaner and spray the shi out of the inside of the ICV, plug the ends and shake it aound. Should have a little 'tap' noise to it when its clean.

if that dosent work, theres always the good old penny trick. take a few pennies, and drill a hole in each one. start with a 1/4" hole, then make a few larger, and a few smaller. place the penny in the vaccum line that comes from the intake bellows to the ICV [place the penny agaisnt the opening for the ICV] try 1/4" first. If the idle is too high, use a smaller hole, too low use a larger hole. Keep trying until the idle is around 650 to 700 rpm.

WAAAAAAAAAYYYY cheaper than a new ICV

[Keven]

Thanks Joe, ill let you know tomorrow!

[Adrian_Visser]

trusty penny trick i never did get around to doing that to my '84 eta

[e30trooper]

hey i unplugd mine and my idle went high, does that mean it works?

[Hick]

kinda. may need cleaned out

[e30trooper]

ok cool, im going to just replace all the hose lines cuz i know some are really old cuz they are hard as a rock. I bought some intake cleaner, a spray like BPC that should work good?

[Kerrath]

I haven't messed around on an M10 to know this, but I know the throttle switch on Volvo 240s and M20's can be adjusted and can put the car in power mode even at 0 throttle. This throws the RPMs up to like 2-3k depending on how open it is. I know M50s have no adjustment screws so they can't be adjusted so its possible your M10 isn't adjustable either.

[e30trooper]

do you mean advanced timing? or maybe theres a screw on the intake somehwere i can ajust, this is my 1st bmw

[Kerrath]

On the throttle body, there's a switch that rides on the shaft that opens and closes the butterfly valve. If the switch is adjustable (2 screws, one on either side of it that loosen it so you can rotate the switch) then it's possible to trip the switch so it tells the ECU that the throttle is open when in fact, the throttle is fully closed. When this happens, depending on the degree, it can make your idle be any where from 1500-3000rpm pretty easily. (I did this to my volvo accidentally when I adjusted it as close as possible for better throttle response. My friend's E30 started doing this also after we put the head back on. His is an M20 though.)

Since the ecu no longer thinks the engine is at idle, I'm pretty sure it wouldn't use your ICV any more. Unplugging it could get the valve partway open and delivering some extra air.

At any rate, even if it turns out not to be the problem, it's pretty easy to check out. With your engine off, pull the throttle lever on the throttle body gently. If the TPS is adjusted correctly, usually you will hear a click noise. Some TPS don't click though so without knowing much about m10s, I can't say for sure.