Jimjacqmx5

strange one.

My 964 has suddenly begun dying intermittently but only when it is wet. Started last week after a track day, an excursion into the mud and subsequent under car serious steam clean BUT
Car ran perfect for another hour of tracktime after the wash.
Car drove 200km home after track day until 5km from home when in a downpour it played up.

Symptom
Driving along and then it just slowly snuffs out but still idles. As soon as you touch accelerator it dies. BUT
Stop for a few minutes and then it goes fine. After initial time of acting up, it was dry for a week and car drove perfectly including over sn hour if flat out driving around the race track. Car has MAF conversion and pod and we wondered whether water was getting in to system through pod BUT MAF pod has been in for a while without issue.

I can only assume water is effecting electrics somehow but all electrics I can thinking are in engine bay which remains totally dry.

Help

Magblixt

I have heard that the earthcable on the transmission can be a weak point and can cause this kind of problem.

jimq

is the O2 aftermarket? Sounds like something that could be the cause from other post. Water can get into them.

Jimjacqmx5

O2? Do you mean oxygen sensor?

Babalouie

I wonder if it's an ignition issue. As in, press throttle, it adds fuel, but snuffs out the weak spark and dies.

There are two plugs for the ignitors, which are on the left hand side of the engine bay, tucked quite far in. The plugs for them point upwards, and I suppose if water got in there they might stay there. To remove the plugs you press in this retaining hoop, and pull the plugs downwards. Maybe there is just some moisture in there

Rocket Rob

Yes, oxygen sensor. There have been problems with water reported with aftermarket oxygen sensors. Switching to a factory original seems to resolve it.

StanUK951

I had a similar issue. I initially thought it was linked to damp weather too. I changed the coils, distributor caps and rotor arms, the air flow sensor and all manner of things. Eventually had the o2 and cylinder head temp sensor changed, one of these cured it...

Jimjacqmx5

Thanks for all your replies.
I think I'll try the O2 sensor first and then get some coils.
The coils are pretty old I gather. I've had the car for four years and never changed them and I'm prety sure the guy previously didn't.
Seems definately to happen when it is wet though.
The way it dies it feels like a poorly functioning MAF as it loses all ability to create power but still idles. As soon as you press accelerator it chokes. Why it would only happen when it is wet I have no clues.
Water wise, the engine bay is TOTALLY dry, even after the heavy rain and no water got in the main engine area when I was washing it. That said, I know when I sprayed it for ages with the high pressure hose, the whole of the car steamed up so perhaps some moisture got in somewhere? I would think though that the issue would still remain when it is dry though?

I hate little issues like this, they drive you nust as you never know when it'll strike.

Grrr

alexjc4

eek your car may have rabbies
http://en.wikipedia.org/wiki/Hydrophobia

seriously though, sounds a lot like an ignition issue as others have said, maybe caused by dampness/fault in the HT circuit or a bad earth.

evoderby

As others have said, 99% the O2 / lambda sensor.

The reason I am 99% sure is because of the fact that the problems play up in extremely wet circumstances...yet the car starts without problems after stalling.

This is because the Motronic doesn't 'listen' to lambda input during start up...as soon as it does after 30 seconds of running or so the problem returns.

A bad coil on the other hand is 'bad' all the time. Also there are two of those on the 964. Colin's dyno sheets show that the 964 engine performs quite well on only one functional coil only losing about 15HP top end power in the process. For two coils to simultaniously go bad at exactly the same time would be rather unrealistic...

alexjc4

You could eliminate the o2 sensor quickly by unplugging it (next time the problem manifests itself) and seeing if it the issue remains. If its a heated type o2 sensor you do not want to run for long with it unplugged as that will kill the sensor.