m50 missing and backfiring intermittently

[JGood]

Some gauges have electric senders. otherwise you can just run an extra long fuel line and run it outside of your hood. But intermittent still mean you might have low fuel pressure all around.

Also, I'm starting to suspect your TPS. I didn't read if you swapped that out.

Nope, I'll add it to the list. What if I just unplug it? I know the throttle response from on/off throttle will be poor, but it should eliminate the missing at mid RPM if the TPS is causing it, right? Reason I ask, is I don't have access to a known good spare.

[JGood]

Not sure if it's a major concern, but 2 or 3 of the spark plug holes had some oil pooling in them. Which is weird, as the valve cover gasket is fairly new. I cleaned the oil out of the boots and plugs before reinstalling them, and it still missed during the test drive, so I don't think that's the cause.

[shiboujin]

clean the inside of the boots, get new spark plugs. fix the leak. it's probably a messed up gasket between your spark holes. That will cause a misfire fyi. Your VC might be warped.

[dude8383]

Check your crank position sensor. I had similar symptoms. Should be fairly easy to pull it out of there and test with multi-meter.

[JGood]

Check your crank position sensor. I had similar symptoms. Should be fairly easy to pull it out of there and test with multi-meter.

It's not easy to pull off, but it's easy to check with a mutlimeter :) I didn't think of that, I figure to run as well as it does 99% of the time, it would be within spec (540 ohms +/- 4 IIRC?)

clean the inside of the boots, get new spark plugs. fix the leak. it's probably a messed up gasket between your spark holes. That will cause a misfire fyi. Your VC might be warped.

Got the spark plugs today. The gaskets are new, I installed them carefully. I'll try to make sure everything is seated properly.

[xwill112x]

the reason i asked if you had removed your injectors is because sometimes the rubber seal will get pinched or get brittle and cause a vaccum leak when you removed them. causes drivability issues as you explain to have. just a thought.

[dude8383]

It's not easy to pull off, but it's easy to check with a mutlimeter :) I didn't think of that, I figure to run as well as it does 99% of the time, it would be within spec (540 ohms +/- 4 IIRC?)

LOL, well I did it just recently, it wasn't too bad.

[JGood]

LOL, well I did it just recently, it wasn't too bad.

I guess it could go smoothly. I have a bare m50 block sitting in my garage with a CPS corroded in place so hard, that I can't get it out. That's the first thing that came to mind when you said that, haha. I guess there should be enough room in the engine bay to get to it if it's not stuck.

[JGood]

Replaced the plugs. Must have looked over it before, but plugs 2, 5, and 6 looked a little wet and smelled like gas. The car was sitting all day and I only had it running to pull it into my garage, maybe 30 seconds. Not sure if that matters.

I took it for a drive, and it missed once throughout the 10 minute drive. Then at a stop sign, I felt a slight missing at idle. It only did it at that one stop sign.

I'll have to drive it to work tomorrow to really get a feel for things and see how it acts.

[richardb]

Still sounds like coil packs. The hamburg technic set is cheap for set of 6. They even come with new coil rubber boots which are like $8 each separate. So it's a good deal. The missing and backfiring sounds like coils. Maybe it's the wrong approach but sometimes you have to throw money at things when doing it yourself or pay a shop to diagnose it.

[JGood]

Still sounds like coil packs. The hamburg technic set is cheap for set of 6. They even come with new coil rubber boots which are like $8 each separate. So it's a good deal. The missing and backfiring sounds like coils. Maybe it's the wrong approach but sometimes you have to throw money at things when doing it yourself or pay a shop to diagnose it.

Aren't they ~$45 each? I wouldn't consider $270 a cheap thing to just throw at an engine to see if it fixes a problem. Maybe if fuel pressure tests out OK, I'll look into that.

The way the car misses doesn't feel like a normal miss. It's like I totally lose power for a full second or so. You can feel it as much as you can hear it... the car bobs around a bit from going from 3/4 throttle to no throttle back to 3/4 throttle. A single cylinder misfire usually just is a little pop sound that you can't really feel, from what I've experienced.

[FredK]

Nah, Bremi or Bosch coils are around $45 each.

The Hamburg Technic coils are around $150 a set off Ebay.

I'm in the middle of diagnosing a similar problem on a 94 325i. It definitely hesitates for a full long second, and you can hear something through the exhaust as it's busy sucking at life.

[JGood]

Nah, Bremi or Bosch coils are around $45 each.

The Hamburg Technic coils are around $150 a set off Ebay.

I'm in the middle of diagnosing a similar problem on a 94 325i. It definitely hesitates for a full long second, and you can hear something through the exhaust as it's busy sucking at life.

I see. Still a decent chunk of change. How are those coils quality wise, pretty good?

My engine is from a 94 525i. What troubleshooting have you done so far?

[richardb]

Yeah the coils are great. Had them for a year before I sold my car recently. Can't beat $150. Like I said boots are $8-$9 each ($48-$54) PLUS $4X each coil elsewhere. If you factor in the boots it's really only $100 for new coils. Did you check fuel pressure and smoke test for vac leaks?

[JGood]

Ugh. Drove the car to work today, it didn't skip a beat for the entire hour drive. I guess I shouldn't complain, it would just be nice to fix whatever is wrong and get it over with. Because I'm sure it will come back.