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

[Cinnabar325is]

My crank sensor gives me this problem every now and then. If I wash my motor I get the same reaction as in heavy rain.

Interesting. I wonder how the water would interfere unless the wiring/sensor were damaged? My CPS is brand new... but you never know.

[EREKSHUN]

My crank sensor gives me this problem every now and then. If I wash my motor I get the same reaction as in heavy rain.

[InfiniteDice]

Check your O2 sensor leads for cracks, exposure that can short out.

I had this issue after getting a totally custom exhaust with headers that put the o2 sensor further back. I essentially lengthened the leads to the o2 sensor and used heat shrink/tape to seal it.

I was driving through lots of water on the highway to work one morning and the same thing happened. It died, so I restarted the engine coasting on the highway and tried to put it back in gear... if I applied any pressure on it it died again. I coasted off at my exit and restarted at the lights.

I could smell excessive gas, it did restart but I had to feather between revving the engine and letting it slip into 1st to get moving. Once I made it to the parking lot I left it for the day and for my drive home it was totally normal.

The next time it was raining it started doing it again so after some deductive thinking I unplugged the o2 sensor under the hood and drove home... NO ISSUES.

I still need to rewire the leads and what I have planned is to use the heavy duty heat shrink tubing that contains a glue on the inner surface, this really seals and will not allow water to ground out the leads.

The o2 sensor controls your fuel mix, and it is making the computer run extremely rich by sending incorrect fuel/air signals.

Hope this is useful!

[BMWManiac]

This may be random, but check your battery terminals in the rear and make sure you have a solid connection

[mbonanni]

lol oh i see what you thought I meant. yeah, I don't think a spray bottle on the hood would do very much damage.

It would cool the hood off a little perhaps.

Goodluck getting your problem resolved

[Jaxx_]

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

lol oh i see what you thought I meant. yeah, I don't think a spray bottle on the hood would do very much damage.

[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.

[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?

[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.

[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)

[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?

[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.

[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.

[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.

[5Toes]

hose is