1989 M20B25 only starts with the AFM and Temp Sensor unplugged, no other combination will work. The temp sensor is brand new, and the afm is known to be working, as I rode in the car I got it from. I am beyond confused, if anyone has any suggestions they would be much appreciated. Sent from my iPhone using Tapatalk
Announcement
Collapse
No announcement yet.
Only starts with AFM and Temp Sensor unplugged.
Collapse
X
-
Originally posted by tomstin View PostHate to sound like a broken record recently. What happened prior to this problem? Coming out of storage? Car is new to you? Was running fine, then died? All may be hints as to what's going on. Strange that unplugging those would get the car started?????
After the swap it started right up and ran perfectly for about an hour, then just cut out and died. It was really difficult to get it started after this and it died almost immediately when I managed to. I figured since I know the engine and surrounding stuff works, it must be a fuel problem. So I tried to fix it by:
-New fuel pump
-Drained the old fuel
-New fuel filter
-New main relay
-New fuel pump relay
After this it still wouldn’t start, unless the afm and coolant sensor are unplugged. When and only when they’re both unplugged, it idles perfectly, is responsive to throttle/doesn't bog down, and drives until it warms up, then gets funky and dies. I assume because it’s running off the default ice cold temp map with those sensors unplugged. When one of them/neither is disconnected it cranks very strong but never turns over.
Here’s a list of other recent work in case that helps solve anything:
-New spark plugs
-New spark plug wires
-New cap and rotor
-New ignition coil
-New intake boot
My only guess is either I somehow didn’t tighten the manifold down correctly and there’s a massive vacuum leak (which I’m about to double check) or it’s some weird wiring/electrical thing.Last edited by buttery_flakey; 04-02-2021, 06:02 AM.
Comment
-
Originally posted by tomstin View PostI believe the wiring harness is different. Research some of the swap threads.
Comment
-
Originally posted by moatilliatta View PostYou can check biger vacuum leaks with starting fluid, Danger to manifold. Is the AFM door swinging smoothly?
Comment
-
I would avoid further troubleshooting with the AFM and coolant temp sensor unplugged. You know those parts are good and you are only confusing your DME by leaving them unplugged. I would plug them back in and crank the car for a while to see if you can get it started up. Regardless, you may need to perform some electrical tests since you are confident there are no vac leaks. I would perform the DME electrical troubleshooting tests in the Bentley repair manual to see if you can isolate which signal is not getting there. I would first suspect your TPS is not adjusted correctly and your DME would not ever know its supposed to be at idle. I would also suspect a failing CPS sensor, which is common to fail and cause a no start condition.Owner - Bavarian Restoration
BMW and European Electronics Repair and Restoration
www.BavRest.com
My Feedback Thread
Our Facebook!
Follow our Instagram!
Comment
Comment