1986 325es

[Bignpk]

Hi guys, I just purchased my second e30. This car is in over all decent shape. 1986 325es, 5 speed, 42,000 on dash. Purchased from original owner, and he had it at a shop which doesn't specialize in euro cars by any means. They couldn't figure out what's wrong so he sold it. Here I am with the car, it starts and revs freely but sitting at idle it just goes up to approx. 2-3k rpms and then falls and goes back up, it seems to continually do this even once warm. The check light flashes for coolant which I've added and replaced a rotten line in the process. I have checked TPS and ICV. Both are clean and seemingly functional. I've checked for air leaks with most vacuum lines being newer I have not found any. Any suggestions on what tests to perform from here? Thanks

[CrashandBurn]

This may sound silly, but.....put a hose clamp (near the middle)on the rubber line going TO the ICV. With engine running, tighten down on the hose clamp. If the engine starts idling normally, you have a bad ICV.


Saw a guy do this on a 1986 325e and he just left the clamp there and the car idles like a champ. He could losen the clamp and the idle would go up or tighten and the idle would go down.


Worth a shot!

[MrBurgundy]

how did you check the tps and cps

[SteveO]

I had a simmilar issue with my M20b25 that would not idle. In your case it could be the ICM (idle control Modual) green box i think beside the ecu?

would reccomend to perform a smoke test however

this is the process that i went through. to find the issue with my idle

the Penny trick will most likely work to calm down the idle if you need to drive it



From Bcbimmers: http://www.bcbimmers.com/forum/showt...321#post291321

1987 325i m20b25

the other day when I turned on my car it shot up to like 3000 rpm and held it there for a few seconds. after 10-15 seconds or untill i give it some gas it goes into this weird state where the idle bounces from like 1500-2200 when its cold and like 1200-1800 when its warm.

Heres a video of me driving and putting in the clutch.

http://youtu.be/R0o6U7TPOZY

it also has a really jerky idle and a 1% press of the throttle registers as like 15% so its hard to be coasting down a road. But once it is past that and above 2000ish rpm it seems to drive fine and the throttle works as normal untill the rpms are brought below 1200 and i assume the ICV opens up to bring the revs back up. If i let it do its own thing in a parking lot with the clutch out in first gear it will drive up to 1800 rpm and coast back down to 1200 then back up to 1800 and repeat.

• Ive tested the TPS and it registers the idle state and the WOT state as it should.

• I tested the resistance values on the ICV valve and they are within spec. I pulled it out to give it a clean as it was really dirty but it did not make any difference after i cleaned it. below is a pic of what the ICV looked like before it was clean.

• I swapped out an new air intake boot as it had a small crack in one of the bends but did not make a difference. Cleaned the throttle body I've looked for cracks that might cause vacuum leaks and sprayed carb cleaner around but did not find anything.

• I also pulled the dipstick and the oil cap to force an intake leak but the idle did not change at all. (I'm thinking there must be a huge hole somewhere??)

• Tested the coolant temp sensor at the resistance values at cold come in at 3800 ohms I think... (at the 20k Ohm scale it reads 3.8 would that mean its 38000 ohms??)

I'm at a loss as what to look for next. it would be nice to be able to swap out the ecu or idle control valve but I don't know anyone up in Prince George that has an 87 325i

I was thinking of taking it into a shop to have the intake smoke tested to see if they can find any sort of vacuum leak or atleast rule that out. But the way the idle is acting it has me thinking that its the idle control valve opening and closing to make the rpms jump up and down regularly like that. or something is causing the ICV to do that.

Any suggestions as to what could be causing this? or what I should do?

On E31 850s I have seen surging issues caused by failed Fuel Pressure Regulators and
mass airflow sensors. Not E30 familiar but worth checking maybe. If you have a FPR, run car for 30 secs then shut off and remove vacuum hose from the FPR - if its wet inside hose or fuel drips out FPR has failed. FWIW...

This is what my car does if I disconnect my maf plug. (Airflow meter plug in your case) Also check to make sure your idle air controller is working. It should hum with the ignition turned on. Other than that I would think a small vac leak could be the problem. Try tightening all the hose clamps, the slightest leak can cause problems like this.

Well today I pulled off the vacuum line to the Fuel Pressure Regulator and it changed nothing at idle. So I assume that its either broken or i have no vacuum in the entire intake system at all. I have a new one on order and will be here on Tuesday and ill swap it out. Ill try and look harder for more intake leaks but lets hope its just the regulator. Can't hurt to have a spare either.

If I had a humoungous vacuum leak would it even be able to run at all? Could it be like the brake booster? My brakes seem to work fine. Questions Ill probably find out the answer to tomorrow.

I pulled the connector to the afm off just to see how it ran and it definately did not like that at all. Stalled out pretty quick unless I gave it some gas. The idle control valve seems to be working and the motor [on the ICV] brings it to a certian [very open] spot when I had it not connected to the intake boot.

It sounds like a vacuum leak. Check all the vac hoses, and don't forget to check the hose at the bottom of the throttle body, its hard to see. I had a similar issue on my 90 325i and I finally found that hose down there, the hose clamp on it was loose causing a very intermittent idle issue, but it ran fine off idle.

Just had it smoke tested by a shop and there was no vacuum leaks anywhere except for a super small leak where the throttle body valve shaft pivots on the throttle body.

From: http://www.verrill.com/car/e30_idlefaq.shtml

Start the car. Run the system "open loop" by pulling the electrical connector from the ICV. The RPM's should climb to about 1500-2000, and then oscillate back and forth between about 600-1500rpm. If reconnecting the electrical connector has no effect on RPM's, your ICM is probably at fault. (For the curious, your RPM's fluctuate because when the ICV is disconnected, the valve is stuck wide open, and the DME is the only thing controlling your idle. The RPM's rise until it cuts the fuel flow, which causes RPM's to dip. Then it restores fuel flow, and the cycle begins again.)

When I unplug my ICV it the car dies immediately and makes a weird clicking noise and will not start at all. My car does basically the above described example this when the idle control valve it is plugged in. Im beginning to lean towards it being the idle control valve. Not exactly the cheapest part to check and see if its working

Well thank the fuckin beaver.
Drilled a 1/4" hole out of 5 cent coin and jammed in one of the hoses that connects to the idle control valve. In a semi warm state it idled at 900-1000 ish and swapped out to a 5cent coin with a 9/32" hole and it idled at 1200ish. Ill use the 1/4" hole one for now but the feeling when you can hear the car "idle" and not have it bouncing like crazy is soo nice.

Have to see this weekend if its actually the idle contol valve that is malfunctioning when I swap it out with bluebeamer's.

But this is a nice temporary fix.

Well, met up with Carson, bluebeamer, and we tested out a couple Idle Control Valves but did not make any difference. So then we tried swapping out an ecu that he had at it fixed the idle. Very relieved that I 100% know what the issue is now.

So now I will be looking for a fully working 153 or 173 ecu. If anyone has an extra I will gladly buy it!! Ill be traveling though Vancouver around the 18th of December and be on the Island after that. If no one has one i'll try Bimmer parts in Duncan too. Just glad to have figured out the problem