glenncof

1985 911K at 206Kmiles

I don't really know if wet weather is related but my Cab has been outside in rain for several days. The problem has occurred first thing in morning and usually goes away after warm-up. I assumed cap/rotor with condensation.

The problem is stumbling and no rev condition.

Today, no problem start but after 1 mile it died at stoplight / no idle. Then another mile dies again, won't start.

Came back later, starts fine/idles but after 1-2 minutes starts to stumble again, like severe missing, can't rev. Got it started and kept reving until fully up to operating temp. Problem never cleared up. Even while reving, engine doesn't have power to push the car.

Pulled dist cap, inspect cap/rotor...not bad. Wires in good shape. Visually checked grounds at Cyl 1 on engine and behind fuel filter...look OK. Idle Control Valve vibrates when ign switch on, so DME is powered.

Electrical checks next:
1) Verify solid 12V at ign coil.
2) Ohm tests on coil, not sure this is conclusive though.
3) Ohm tests on sensors.

But, I don't expect to find anything w/these tests.

Once I get past these....where to next .

Any similar experience ?

Steve Weiner-Rennsport Systems

Hi,

Can I assume that it starts & runs flawlessly in dry weather?

1) Check or replace DME relay; those can be troublesome.

2) Check the grounds on the intake manifold.

3) How old is the cap, rotor, and wires??? Visuals don't help much here.

rusnak

I wonder if there is a massive vacuum leak somewhere, like maybe a crack in a vent hose or missing hose clamp? Also, is the line to the fuel pressure regulator connected? If you have a spare DME relay (and who doesn't?), time to change it out.

Ed Hughes

I bought a set of new wires a couple of years ago from a known performance company in the Porsche world. If there was even a thought of them getting wet, the car was a pain to start. They made good on the problem, but that was with a set of brand new wires. So, like Steve says, a visual or assumption of something being good means nothing.

glenncof

Haven't fixed it yet but I found more water under driver seat than expected (What 25yr old daily driver, convertible doesn't leak?) Not raining today so drying it out. Yes, ran flawlessly until LOTs of rain. Wires last replaced at 132K with Beir, these replaced originals. Dist cap/rotor with Bosch at 153K.

Meanwhile:
Cleaned/sanded terminal lugs at two grounds in engine compartment.
Removed coil, checked ohms (0.55 & 5.5K), & cleaned terminals/lugs. Confirmed full voltage at #15 terminal.
Measured ohms on speed/ref mark sensors (1-1.1K)
Removed DME relay, dried on hot air register. (It doesn't look hermetically sealed from outside.)

Seems a little better<at least idles now> but if condensation in DME it will take more than afternoon to dry it out.

I was thinking of measuring the 12V out of relay to DME. Just not sure which is +B feed. Looks like pin 87 on relay (this is DME #18). Is this the feed for injectors also ?

rusnak

whoa. hold on there.

Water under the drivers seat? Like, next to the DME brain?

Ed Hughes

No shi-ite. Computers and water aren't a good mix. If a cab is leaking that much, I think that needs to be addressed if the poor car has to sit outside. Standing water under the seat is not normal.

theiceman

Well i would humbly suggest fixing the absolutely obvious before pushing on further .. unless you ordered the indoor swimmimg pool intentionally

Steve Weiner-Rennsport Systems

REALLY good advice.

All bets are off if the ECU gets damp or wet, Sir.

Dry the ECU in the house for a day and fix those leaks.

dshepp806

How much water, exactly? Did it get anywhere near the DME?

Doyle

whalebird

Yep...get after those leaks and don't forget the windshield gasket - especially the lower corners. Make sure the brain is dry and the ground lugs ( there is a ground under the seat IIRC) are clean and dry.

rgoodrich

I'm in the desert, and we recently had some actual rain. Most of the guys around here park it in a garage when the wet stuff comes down, but my 81SC is my daily driver. I'm told that water can come into the engine through the grill and get the distributor wet, thereby stranding you in the rain. Surely it must rain in Germany, or everywhere else besides here. Do you guys park your cars when it rains, or is this a myth?

rusnak

I think the window glass to roof seals might be leaking, or the top itself. If the window scrapers are leaking, then water can actually get inside the door, but usually drains back out to the outside. Any water under the drivers seat can indicate a problem with the DME brain.

I would check the floor for removed screws, and silicone any holes up before driving in the rain.

Ed Hughes

911's can certainly take rain, car washes, etc. But the OP's description of standing water near his DME is most likely his issue and is a condition that needs to be remedied.

rgoodrich

Thanks, Ed
I'll take it out when it rains again next year!