taube
08-23-2023, 05:22 PM
Hi everyone!
Over the last few weeks, I've been scouring the forum for info to help diagnose and solve my intermittent misfire problem. I've now reached a point where I have checked everything that I understand (which is not too much unfortunately) and could really use some guidance and/or discussion partners to figure out the next steps. Disclaimer: I'm not afraid to get my hands dirty, but this the first car I've ever worked on myself. I'll go to a professional if and when it is necessary, but it takes weeks to get an appointment anywhere at the moment so I'm trying what I can in the meantime. I also enjoy the learning process :)
The car: 1995 E36 318i convertible (euro, manual, m43b18 engine, ~125.000km)
The issue: Intermittent misfire >~120kph/~3500 rpm
It only starts occurring about 15-30 minutes after operating temperature has been reached. Occurs at different speeds/rpm in a seemingly random manner, but never when accellerating/WOT. If I back off the throttle, it stops and often doesnt return when I get back on it. I do feel like the car runs slighty rougher at highway speeds once the problem starts occurring, but at this point I'm starting to think every bump is a symptom. Runs fine when its cold and I feel no clear hesitation in acceleration or lack of power at any point (other than normal for a 318i:)). I've had multiple mechanics comment on how well it runs in fact.
Things I've tried:
- Brought it to a mechanic, who read the codes (its OBD-I and I cannot do this myself) and said the lambda sensor needed replacing, which they did. They test drove it and said it ran good and could not reproduce the problem. As I said it only really occurs after the car has been warm for a while, so maybe they never got to that point.
- The coil pack had corrosion on one of the leads, so I swapped it with a second hand part. I've been told these coil packs are pretty durable and the dealer I bought it from said it was good, so I'm trusting that for now.
- The spark plugs looked fine, but replaced all of them for good measure.
- Replaced the fuel filter.
- Measured fuel pressure (after the filter was replaced) and it seemed a bit high with the engine on, so replaced the fuel pressure regulator.
- Measured the MAF and IAT, which seemed fine
- Measured resistance on the injectors, which all read 15.9 Ohms. Did find some oil in a few connectors, which puzzled me but it hasn't come back since cleaning it. I checked the wire harness for oil creeping up through it but the wires running to the injectors were bone dry. (Could it creep up on the inside of the insulation?)
- I've also recently cleaned the ICV and Throttle Valve and replaced the rubber intake boot and vaccuum lines from and to ICV.
Addtionally: it used to run without MAF connected, but right now it starts but immediately dies. This suggests to me that something is wrong even if the MAF is bad.
In conclusion: Unfortunately, the problem persists and I am clearly out of my depth. So far the parts have been cheap (apart from the lambda sensor) but I'd like to avoid randomly throwing more parts at it. I dont think it is a compression issue, as I would expect more consisten problems (right?) My latest theory is that maybe the crankshaft sensor is going bad? I've read some posts that were similar to mine of people only having issues at high rpm and it being very random. The fact that it takes a while after reaching operating temperature before the issue starts occurring, suggests to me that it is a sensor somewhere outside the engine that thus takes longer to heat up.
If you're still reading at this point, thank you for your patience and I would be happy for any guidance you might be able to give me!
Cheers and sorry for writing half a novel.
Over the last few weeks, I've been scouring the forum for info to help diagnose and solve my intermittent misfire problem. I've now reached a point where I have checked everything that I understand (which is not too much unfortunately) and could really use some guidance and/or discussion partners to figure out the next steps. Disclaimer: I'm not afraid to get my hands dirty, but this the first car I've ever worked on myself. I'll go to a professional if and when it is necessary, but it takes weeks to get an appointment anywhere at the moment so I'm trying what I can in the meantime. I also enjoy the learning process :)
The car: 1995 E36 318i convertible (euro, manual, m43b18 engine, ~125.000km)
The issue: Intermittent misfire >~120kph/~3500 rpm
It only starts occurring about 15-30 minutes after operating temperature has been reached. Occurs at different speeds/rpm in a seemingly random manner, but never when accellerating/WOT. If I back off the throttle, it stops and often doesnt return when I get back on it. I do feel like the car runs slighty rougher at highway speeds once the problem starts occurring, but at this point I'm starting to think every bump is a symptom. Runs fine when its cold and I feel no clear hesitation in acceleration or lack of power at any point (other than normal for a 318i:)). I've had multiple mechanics comment on how well it runs in fact.
Things I've tried:
- Brought it to a mechanic, who read the codes (its OBD-I and I cannot do this myself) and said the lambda sensor needed replacing, which they did. They test drove it and said it ran good and could not reproduce the problem. As I said it only really occurs after the car has been warm for a while, so maybe they never got to that point.
- The coil pack had corrosion on one of the leads, so I swapped it with a second hand part. I've been told these coil packs are pretty durable and the dealer I bought it from said it was good, so I'm trusting that for now.
- The spark plugs looked fine, but replaced all of them for good measure.
- Replaced the fuel filter.
- Measured fuel pressure (after the filter was replaced) and it seemed a bit high with the engine on, so replaced the fuel pressure regulator.
- Measured the MAF and IAT, which seemed fine
- Measured resistance on the injectors, which all read 15.9 Ohms. Did find some oil in a few connectors, which puzzled me but it hasn't come back since cleaning it. I checked the wire harness for oil creeping up through it but the wires running to the injectors were bone dry. (Could it creep up on the inside of the insulation?)
- I've also recently cleaned the ICV and Throttle Valve and replaced the rubber intake boot and vaccuum lines from and to ICV.
Addtionally: it used to run without MAF connected, but right now it starts but immediately dies. This suggests to me that something is wrong even if the MAF is bad.
In conclusion: Unfortunately, the problem persists and I am clearly out of my depth. So far the parts have been cheap (apart from the lambda sensor) but I'd like to avoid randomly throwing more parts at it. I dont think it is a compression issue, as I would expect more consisten problems (right?) My latest theory is that maybe the crankshaft sensor is going bad? I've read some posts that were similar to mine of people only having issues at high rpm and it being very random. The fact that it takes a while after reaching operating temperature before the issue starts occurring, suggests to me that it is a sensor somewhere outside the engine that thus takes longer to heat up.
If you're still reading at this point, thank you for your patience and I would be happy for any guidance you might be able to give me!
Cheers and sorry for writing half a novel.