Hi Guys,
Sorry for dropping this in the wrong section first time.
I did an M50 swap to my 88 E30 a couple of years back and have been fighting an idle issue ever since. I don't think this is vacuum leak related. When the problem is at it's worst, the car will stall when you take your foot off the gas, or if it does not stall, the revs drop to almost nothing before recovering. Everyone is thinking vacuum leak about now, but I don't think so.
The symptoms go away completely for a week (about 100 driving miles) after I disconnect the battery and reconnect. I took the intake manifold off and replaced the seals and hoses with no change in the problem. When I disconnected the O2 sensor, the issue went away for about a week. I reconnected the O2 sensor and replaced the 413 ECU with a spare 413 ECU. I thought that was the issue because the car ran beautifully for a week and then the problem started to come back again slowly.
When I first start the car, it idles fine for about 10 seconds and then the anti-lock warning light comes on and the idle stumbles at the exact same time. I was thinking that the wiring may have been messed up with the O2 power feed possibly interfering with the anti-lock power but I cannot find any way that could happen.
It seems like any time the ECU has been run a while, it learns parameters that just don't seem to work for the car. If reset, it runs fine until it's had a chance to relearn the system. I've swapped idle control valves with no change and I've played with the throttle plate adjustment to keep the car alive and running, but it's still not right. After a computer reset, the car drives beautifully but after a couple of days, you get that first dip in engine speed upon taking your foot off the accelerator and you know the problem is coming back.
I'd love to solve this issue once and for all. I checked the throttle position switch and swapped out a different one with no change. Both of them have the same values though with a 1.2k-3.8k range which is outside of the book spec of 1k-4k. But it sweeps smooth with no dead spots. Lately, I've been wondering if the 1.2k base is causing the ECU to think the throttle has not closed and is coming late to enable the idle control valve.
Does that sound plausible? If not, any other sensors you can think of in the system that might cause this?
Thanks in advance for any help.
Tim
Sorry for dropping this in the wrong section first time.
I did an M50 swap to my 88 E30 a couple of years back and have been fighting an idle issue ever since. I don't think this is vacuum leak related. When the problem is at it's worst, the car will stall when you take your foot off the gas, or if it does not stall, the revs drop to almost nothing before recovering. Everyone is thinking vacuum leak about now, but I don't think so.
The symptoms go away completely for a week (about 100 driving miles) after I disconnect the battery and reconnect. I took the intake manifold off and replaced the seals and hoses with no change in the problem. When I disconnected the O2 sensor, the issue went away for about a week. I reconnected the O2 sensor and replaced the 413 ECU with a spare 413 ECU. I thought that was the issue because the car ran beautifully for a week and then the problem started to come back again slowly.
When I first start the car, it idles fine for about 10 seconds and then the anti-lock warning light comes on and the idle stumbles at the exact same time. I was thinking that the wiring may have been messed up with the O2 power feed possibly interfering with the anti-lock power but I cannot find any way that could happen.
It seems like any time the ECU has been run a while, it learns parameters that just don't seem to work for the car. If reset, it runs fine until it's had a chance to relearn the system. I've swapped idle control valves with no change and I've played with the throttle plate adjustment to keep the car alive and running, but it's still not right. After a computer reset, the car drives beautifully but after a couple of days, you get that first dip in engine speed upon taking your foot off the accelerator and you know the problem is coming back.
I'd love to solve this issue once and for all. I checked the throttle position switch and swapped out a different one with no change. Both of them have the same values though with a 1.2k-3.8k range which is outside of the book spec of 1k-4k. But it sweeps smooth with no dead spots. Lately, I've been wondering if the 1.2k base is causing the ECU to think the throttle has not closed and is coming late to enable the idle control valve.
Does that sound plausible? If not, any other sensors you can think of in the system that might cause this?
Thanks in advance for any help.
Tim
Comment