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'95 Porsche 993 Stalls After Sitting In the Rain

I have a 1995 Porsche 993. The car sat outside in the heavy rain the other day for quite a while. The next day when I went to start the car it stuttered and barely turned over. I gently hit the gas and it took a few minutes to warm up - then it idled fine. I was pulling away and I noticed that it would idle fine but it only seemed to stutter when I hit the gas pedal. After about 20 minutes the effect disappeared and it ran fine. This is the second time this has happed and only after the car sat outside in heavy rain. I have read the other comments about stalling being due to water on spark plugs, wires or in the distributor cap, etc. (mine were replaced less than two years ago) so I wondered if my situation is different because it only seems to happen on acceleration. Any ideas, thoughts or comments?

This sounds like classic worn-out spark plug wires. 1995 is still air-cooled . . . and the engine compartment gets a little hot on an air-cooled. 2 years on plug wires isn’t all that long unless during that time your car sat and idled in traffic, got warm a bunch of times, whatever. First thing I would do is check the wires, but since you’re already there changing six plug wires isn’t a big job. One way you can check defective wires is to “mist” your plug wires with a spray bottle and plain water . . . start the car and spray each wire and listen for the stutter. The barely turning over sound like classic dirty battery connections, easily fixed. May be an old battery, you didn’t mention its’ age. You could eliminate the whole mess and sell me your '95, I’ll take good care of it, I promise. Kidding. Good luck! Rocketman

How old are the wires? I agree with rocketman, that’d be my first guess.

Make that another vote for plug wires especially if they have not been changed in some time.

I am leaning towards distributor cap, but plug wires are certainly an option. I pick the cap because of problems after sitting, if the problem was rough running in wet weather I would second wires.

Thanks to all. I already checked the plug wires (less than two years old) by spraying them (a lot - then soaking them in water) and nothing. Same with the distributor cap - I misted and then soaked with no affect on the engine. I wet a lot of engine parts and wires to see if i could find a short. Nothing. The battery is new and I chedked the connectors - not dirty. So far nothing replicates the effect of leaving the car outside in heavy rain - I soaked the car with a hose (engine compartment closed) and nothing. The stutter only seems to happen after leaving the car outside in the heavy rain AND when I push the gas pedal - does that spark any thoughts on other possible problems?

Have you posted this on one (several) Porsche forums? I bet a 993 owner might know exactly what the problem is, not many (any?) of them around here.

Could you be getting water in your fuel system somehow?

The next time this happens pop the distributor cap loose and note if there’s any moisture inside of it. Heat attracts moisture and, depending on the atmospheric conditions, moisture can accumulate inside the cap after the engine has been shut off. This is a common occurrence and think of it as a window sweating on a cold, damp winter day.

Wipe the moisture out and then see if the thing will start. After that, spray the cap, plug wires, etc. down with the liberal use of some WD-40. That can prevent the problem from happening again, at least on the short term.

Great Comment OK, Make sure you wipe the inside of the cap with something other than your finger, as the residual oil your finger swipe could leave may be enough to cause problems. I have never used the WD 40 solution, but have used a paper towel and hair dryer.

Everything points to a weak spark. I had similar symptoms with a VW Rabbit. And I sprayed water all over the engine compartment to try to replicate it, but it didn’t mind water wherever I sprayed it. But if it rained the car balked on starting and accelerating. Long story, but It turned out to be a crack in the coil. Somehow the rain was able to get to the crack when spraying the engine with water didn’t. The only way to determine if this is your problem is to remove the coil and inspect it very closely with a magnifying glass for a crack.

Threre’s a possiblity this is a gas mixture problem too. Something as simple as water getting into the gas. Or it could be a clogged fuel filter or air filter or clogged exhaust system. When it rains, the incoming air mixture has less air because of the water vapor, which can make the symptom appear.

You should also hve your mechanic check your battery for proper charge and discharge rate (with a load tester), and the battery connections. Sometimes when it rains, these can become problematic and cause weird symptoms.