idle oscillation issues

lumlumty · 10-24-2010, 02:00 AM

Hello,
model E30 325i 1989 with manual transmission
replaced head gasket with new head bolts, resurfaced head, new water pump, new thermostat 80c, m50 type injectors, new spark plug wires, new timing belt, new icv, new intake/exhaust manifold gaskets, new throttle body to intake manifold gasket, new valve cover gasket,

Symptoms from last weekend: idle oscillates from 700 rpm to roughly 2000 rpm when ICV wire was connected. The engine will idle at around 700 to 800 rpm when the ICV wire was unplugged as if everything is normal. I was able to drive the car with the ICV unplugged but it did not keep idle when I stop the car in neutral.
I then left the car until this weekend to work on it.

Today's symptoms: idle still oscillates from 700 rpm to roughly 2000 rpm when ICV wire is connected. The strangest thing is that now when ICV is unplugged engine will now rev until 3800 rpm.
I then decided to change the ICV thinking that it will solve the issue. The new ICV did nothing. I checked all of the rubber tubes and even ducked tape the end of the one that connects from the valve cover to the throttle body. I sprayed WD40 around the area and nothing changes.

I was not able to get the engine light to flash with the stomp test the DME should be a 173 but I am not 100% sure.
I checked all the rubber tubes and also the intake rubber boot for cracks or holes and they seem to be fine. Could it be a sensor problem or a stretched wire? Everything is connected.

I have tried to search different threads but unable to find a definite answer to my problem. My engine might have multiple issues is what I am thinking now. Idle issue along with stomp test not working
Any ideas?

Thanks

lumlumty · 10-24-2010, 02:17 AM

I also installed a new lower temperature thermostat switch in the radiator for the fan to kick in earlier since I did a clutch fan delete.

everlast · 10-24-2010, 12:51 PM

Are you running a chip for the M50 injectors?

Since it sounds like you have a spare ICV, hook it up but don't plumb it into the intake, and look inside to see what its doing.. If you can get it to idle, the ICV shouldn't be moving, at least not much. If its wildly oscillating, then at least you know its the ECU telling it to do so.

Also, use a multimeter and check the TPS, perhaps the ECU doesn't know you're at idle because the switch is malfunctioning.

While you're at it, double check the TPS, ICV, Coolant and Cam position harnesses are all plugged in correctly. Its easy to miss something when you have everything apart. The coolant / cam position harnesses will plug into each other's sockets to, so make sure they're in the right order.

lumlumty · 10-24-2010, 04:20 PM

Thank you for the reply.
I am not running the chip yet. I should br getting one soon when I head out to Toronto.
Since my e30 is out of commission my friend's beater tercel is getting me from a to b at the moment.
This is what I suspect the tps not functioning.
I will try to get a day off and work on my car this Tuesday.
Thanks. I will update the thread after I check it out.

everlast · 10-24-2010, 04:59 PM

You can test the TPS's effect on idle by connecting the idle control valve, pulling the harness from the TPS and manually jumping the connection that TPS closes when you're at idle, the idle should smooth out.

HavocSteve · 10-24-2010, 07:21 PM

Hey jay, you think maybe one weekend you could help me test this out? I don't really get what your saying nor have the tools to check it. Wondering if my idle jumping could be the same problem.

lumlumty · 10-24-2010, 08:52 PM

Thanks Jay I will check it out when I get to my car at my friend/s body shop.
In the mean time I have a spare throttle body that I am playing with at home right now and from what the multimeter ohm test it is faulty.
Oh yes I fail to mention the following that the idle keeps oscillating when throttle is opened ICV is connected. I will keep you guys posted

lumlumty · 11-12-2010, 07:58 AM

Alright the garage did a smoke test and nothing is leaking. It is down to the computer or the injectors. I ordered a chip from Mark D. He has been a great help. He was able to get it out to me asap. The garage where I did the smoke test says that it is the 17 lbs injectors. I beg to differ and suspect that it is the computer craping out. We will see after we put in the chip. The throttle position sensor is ok finally.

lumlumty · 11-17-2010, 11:36 PM

Finally it was indeed the computer that crapped out on me. My car did not even start when I plugged his computer. the next day he installed Mark' chip with the same problem.
Later that afternoon, he called me and said it was indeed the computer. The lesson of this is that i should learn to trust my own instincts more. Thanks Jay once again in giving me a direction.

Wow ac delete, clutch fan delete, minor porting of the manifold, and mark D's eat chip made a difference. It is like driving a new car.
I would definitely buy you a beer but you are in Ottawa.

Cheers