M42 runs like poop in heavy rain

[lolcantturn]

Almost as if water is getting on the coil packs/ spark plug cylinder walls. Literally runs on less than<4 cylinders for sure. I popped the hood in the rain and they were dry. Makes me think it's the O2 heater function then? If the O2 is getting wet then it's producing these results? :| Does anyone else have this problem ?

[Quadrajet]

Do you have the splashguard still? The one underneath between the radiator support and the motor? I was thinking maybe either enough water it getting kicked up to the engine sensor that's by the Harmonic dampener, or the connector is a little loose and moisture is getting to it.

I don't have that splash guard, but I check that connector every so often, because I'm leary of the moisture factor.

[freeride53]

Are you sure it isn't a coincidence?
Have you checked your hoses recently?

[kwill22]

Do you have the splashguard still?

same thing i was gonna say

[bmwman91]

I swear I used to experience the same thing. I think that it is just a case of lousy traction.

MAYBE the rain is cooling the downpipe & O2 sensor enough to cause inaccurate readings. Those things do need to be a certain temperature to operate properly. It seems unlikely that BMW failed to take that into account, though.

[TimKninja]

Still have the sheild sitting under my bench at work, took it off to do the waterpump the day before you bought the kar. Totally forgot about it , it was kinda beat up as well.

It never ran terribly in the rain during my ownership. I could also never get it to idle right as you know But it never ran THAT bad. Maybe the plug wires are arching?

[bmwman91]

I would say that it could be:

- Worn out plug wires that got damp & are arcing
- Dying O2 sensor that is being further messed up by cold water cooling it off
- Imagination

A crappy idle is almost ALWAYS a vacuum leak. If not that, cause #2 is a dead/dying O2 sensor. Beyond that, most things would also cause lousy power delivery at higher RPMs.

[///M42 sport]

I have the same issue. No vacuum leaks. Rebuilt engine. Old O2 sensor which was spliced....

[///M42 sport]

I was thinking the issue might be due to leakage at the hood seal since the relays (fuel, main) are located right against the firewall.

I notice after heavy rain and even at self serve carwashes, I get the irratic idle like it wants to die.

[lolcantturn]

SOLUTION: When I changed my clutch out last summer, the transmission nipped two of my O2 wires and exposed them to each other. In the rain they would arch. Replaced O2, no problems since.

[///M42 sport]

Mine turned out to be a bad coil