Car stumbles/misfires in heavy rain... BUT...

[Cinnabar325is]

I did some searching on here and as I expected, I'm not the first to have this problem.

Background: Car runs fine in the dry and in MOST rain situations. However, if it is really raining hard and I'm on the highway, the motor loses all response and often dies. The strange thing is, if I start the car again (still rolling), it always comes right back to life 100% for at least 10 secs before stumbling again.

The obvious suspect is water/moisture in the distributor. Now the cap and rotor are both new and so are the plugs, less than 10k miles. Others mentioned it could be the plug wires, but my car has done this with two different sets of plug wires.

Anytime I check underhood when this happens, the entire underhood area is very dry, it's not like water is being splashed up on the highway. Especially all the way up to the distributor area.

If anyone has any thoughts or ideas, please share! If it's relevant, the car is running BavAuto wires and Miller GenIII MAF on a 2.8

Thanks.

[RoadWarrior]

Crank sensor?

[Cinnabar325is]

Crank sensor?

Crank sensor is also new (6 months) and adjust to spec. I don't believe water would affect its function unless its housing was cracked or something.

[Jaxx_]

tried replicating the issue with a spray bottle and some water?

[RoadWarrior]

Crank sensor is also new (6 months) and adjust to spec. I don't believe water would affect its function unless its housing was cracked or something.

Yeah. I had a similar problem (none e30) where water would get in the connector. Good luck brudda! Hope you get it figured out.


-RW

[mbonanni]

Spray Bottle =/= Heavy rain

[5Toes]

hose is

[dnguyen1963]

Does your car still have the plastic guard piece? If not, water sometimes can get to the alternator and causes similar problems like yours. My friend had this happened to his Windstar whenever he went over a pothole filled with water. It took us forever to figure it out.

[Jaxx_]

Spray Bottle =/= Heavy rain

Did you read the first post? Under the hood is dry. He doesn't need a lot of water to replicate the issue. I'd be hesitant to spray a lot of water under the hood anyway.

[Exodus_2pt0]

Inspect your coil for cracks. A cracked coil doesn't need to be splashed, the heavy humidity from combining heavy rain and a hot engine is plenty to kill it.

If it is cracked, throw it in the oven at the lowest temp for a while, then seal it up with some black RTV.

[Cinnabar325is]

tried replicating the issue with a spray bottle and some water?

No, but I will give that a shot asap.

Does your car still have the plastic guard piece? If not, water sometimes can get to the alternator and causes similar problems like yours. My friend had this happened to his Windstar whenever he went over a pothole filled with water. It took us forever to figure it out.

Do you mean the undertray piece? My car does not have that, probably couldn't hurt, but I bet they're tough to get in decent condition.

Inspect your coil for cracks. A cracked coil doesn't need to be splashed, the heavy humidity from combining heavy rain and a hot engine is plenty to kill it.

If it is cracked, throw it in the oven at the lowest temp for a while, then seal it up with some black RTV.

I will check this too, thanks.



Anyone else have input?

[BMWManiac]

Does your hood still have the hood seals?

My guess is the water/moisture is coming from the bottom of the car then. I, too, would guess alternator, C101 plug (underneath the intake manifold) or even your ground wire (driver side)

[mbonanni]

Did you read the first post? Under the hood is dry. He doesn't need a lot of water to replicate the issue. I'd be hesitant to spray a lot of water under the hood anyway.

Yes of course I did, did you??

Background: Car runs fine in the dry and in MOST rain situations. However, if it is really raining hard and I'm on the highway, the motor loses all response and often dies. The strange thing is, if I start the car again (still rolling), it always comes right back to life 100% for at least 10 secs before stumbling again.

Says if it is raining it most likely would not happen. I would replicate heavy rain with a hose, with hood closed.

I get what you are saying though. spray bottle with hood open to replicate situation makes sense. I did not think of that.

[Cinnabar325is]

Does your hood still have the hood seals?

My guess is the water/moisture is coming from the bottom of the car then. I, too, would guess alternator, C101 plug (underneath the intake manifold) or even your ground wire (driver side)

Yes, still has all hood seals.

More than anything, it seems like the car loose spark when it stumbles. Could the alternator not working temporarily really affect spark? Long term, sure, but how about short term?

[Exodus_2pt0]

Not really in the short term. Not to mention, I have been in a car when the alternator died... Lights went out before the engine stalled.