Adjust idle?

[applecran]

I've had my 91 e30 318is for about a month now.

I have a slightly rough idle, it does not really fluctuate speed, sits around 800 usually, with a bit of a hickup every little bit.

If i'm at a light or stopped for a few minutes, the idle will slowly drop to about 600-650.

Sometimes (not very often) the idle will actually drop close to 500 and the engine acts as if it is on the verge of almost stalling.  This only seems to happen when I start moving from a light say, and then stop pretty much right away due to traffic, and it is rare but it is the most concerning of the symptoms to me.  I don't want the car doing this when my wife is driving it a she won't know to just give it a bit of gas to get it back to normal.

if I apply the throttle and hold the idle around 1000-1200, it all seems fine, maybe the occasional blip.

It runs great other than that, full rev range, power band seems fine.

There seems to be a slight hesitation if you tap the throttle while idling.

I've done the following, mostly out of routine maintenance I knew the car needed when i got it.  A lot of these things helped a little, at least they seemed to, but it could just be placebo.

All vaccume and air hoses
Many water hoses
water pump
thermostat
temp sensor
coolant
spark plugs
timing chain tensioner
oil and filter
clean icv
tested with known good icv
air filter
fuel filter
Upper and lower intake gaskets
cleaned intake
throttle body gaskets
valve cover gaskets
upper timing cover gaskets
lower oil pan gasket
used my peake reader to check for codes

Next to try is injector cleaner

I have some seafoam, but I'm not sure what to do with it really.  Was going to use it in the crank case, but maybe I can use it elsewhere here.

I also cleaned the engine qutie a bit, removed gunk from the two censors at the front of the engine that had built up.

I'm not sure what to test next.  

Things I've considered doing but i'm not sure exactly how or if they relate to my problem or no:
Adjust the idle - is this possible?
Test Spark plug wires
Test coils
Check Cam timing?
Check throttle cable adjustment

I've also noticed I have an aftermarket exhaust and Cat, not sure if this could cause anything.

Any advice on what to check and how to test some of the above things would be much appreciated.

Thanks

[applecran]

Mods,  I meant to post this in Engine + Driveline.  Can we move it there?  Thanks

[BrandC]

Most likely your vacuum hoses have small hairline cracks or are getting loose at the connections. Just replace them and your idle should improve dramatically. Common M42 issue, so don't worry too much about changing that many parts.

Also, clean the ICV with WD-40

[applecran]

Thanks BrandC.

I actually already replaced all the vaccume lines,and cleaned the ICV with WD-40 - I also tried another ICV that is kown to be good.

The parts listed in my post were all changed already for maintenance (the car was not really cared for by the last owner).

[applecran]

I should mentione,  I've also checked for vacumme leaks using throttle body cleaner... none located, I checked all hoses, throttle bodya nd intake.

[batsbats]

oxygen sensor?

[applecran]

oxygen sensor?

Yeah I thought about that.  Just was not sure if the O2s would cause idle issue like that.

Thanks

[tjts1]

Mine does it once in a while when the engine is cold. Rev the engine a bit and it calms down. I suspect it has something to do with the MAF sensor because everything else has been replaced. Somebody comes on here and reports the same symptoms at least once a week. Seems to be normal for this car.

[EN318isPDX]

Mine does it once in a while when the engine is cold. Rev the engine a bit and it calms down. I suspect it has something to do with the MAF sensor because everything else has been replaced. Somebody comes on here and reports the same symptoms at least once a week. Seems to be normal for this car.

He's right ive been struggling with my M42 idle issues for months. It got progressivly worse until i realized i had to fix it. I did all the same things as you but i did run a cleaner through the injectors off the bat and i think that it made it worse. Just got my brand new injectors today! $27 each not bad price at all! If that doesnt fix it I am not sure what im going to do with it

[applecran]

Interesting.

I'm just running some seafoam through the gas tank since this morning.  I'll see if that helps.

I'll probably also do seafoam through the intake and an O2 sensor (might aswell, don't know how old the current one is).

I'd just like to figure it out.  

What I'm wondering is if I can do any tests on the spark wires etc to make sure they are functioning properly.

[tjts1]

You can check the resistance of the spark plug wires. The problem is the stock wires are 4 feet long and expensive to replace. I installed some relatively new volvo 850 wires for $5.
http://www.m42club.com/forums/showthread.php?t=5309
After a little JY research I found that the M30 engine also uses the same type of plug on the rotor end so those can also make a good alternative.

[applecran]

thanks Justin.  I'm planning on doing a cop conversion at some date.  I'll do an ohm test on the wires for now, and if they need replacing will look for some out of an e30.

I did a pedal code test tonight (i've used my peake on the car before and no codes) and i get:

1262 Idle Speed Actuator

"There is a break or short circuit in the wiring to the idle
actuator or the wire from the DME is defective or the output
stage in the of the DME is damaged. This code will also be
stored if the engine stalls at over 600 rpm."

Now, I've tried to ICVs with no difference in results.  One was mine, one is from a Buddies car that idles fine.

I guess it is possible they are both bad, but I since the other car idles fine, I doubt it.  From the description above it seems it could be a wiring or ECU issue.  Can anyone confirm that or provide more details on how to track something like that down?

[pifane]

Hi!

I got the same problems. Exactly the same. First, you have a little flat head screw with a little bolt on the throttle body. This screw will adjust the rpm on idle!

Second, this things can fix a idle problems but if you have a defective idle control valve, this will not fix you're problem, like me!

My problems is not fixed yet, but it still the same since 1 years...so....this is not my priority for the moment.....i got a bigger problem with cooling...http://www.m42club.com/forums/showthread.php?t=4870

But, you can look over google.com for m42 idle control valve...you will see that 50% of this car owner have this problem...

[AcSchnitzer318is]

applecran... you ever track down a culprit causing this problem.  Quite a few of us dealing with it...