944Time

Ok, this is a problem only when it is raining, or has rained.

My 1986 944 will start, and take me to my half-mile away destination.
Then it is all rough-running and sputtering and popping.

Sometimes it just stalls.

Anyway, it will not restart, until I wait 30 minutes or so. Then it will start and run normally. Go figure!

You can here it sputtering here: https://*******/G1TI
Took that as I got into the shopping center parking lot. The 40-second mark is where the sputtering goes on.

This is an incredibly annoying problem. Any suggestions for what to check?

thomasmryan

you can try to dry out the distributor

mrgreenjeans

- crack in distributor cap
- poor coil wire
- poor wiring to plugs
- cracked or missing insulator boots on the plugs
- cracked or missing white ceramic on the plug itself
- wetness in the distributor cap as mentioned above
- bad grounding points ( there are multiple locations )
- coil is going bad

I would start at the first on this list and go down the line till you have it fixed.
Best wishes with the repair ~ ( and use good, new, Porsche parts, with special attn. to the wiring. They are impedence matched; just heading to rock-auto isn't going to cut it )

944Time

I suppose it wouldn't be a bad idea to pull off the distributor and make sure everything is sorted in there.

But the distributor doesn't get wet -- it is covered up nicely by the hood.

That's what is so puzzling about this problem. It starts, drives fine for a bit, and will re-start fine after a delay.


Here it is starting (from cold) in the wet: https://*******/TeZU
No problems. All smooth and normal.

Here it is starting (at the supermarket parking lot) in the wet: https://*******/0nkb
All sputtery (at 1:08 and around 2 minutes). I drove around the parking lot until I had some confidence it would not leave me stranded on the road.

bonus12

Moisture in the air on rainy days is enough whether it's under the hood or not.

Humboldtgrin

If you take the rain out of the equation then it sounds like a coil going bad.

odonnell

If you want an extra coil for peanuts I have several OEM bosch parts sitting around.

mytrplseven

I'd consider the connector to the AFM. If the connector or AFM contacts are not secure and clean, moisture can cause issues, especially being exposed to moisture. Use a pencil eraser to clean the contacts and inspect the connector wire side for cracks.

944Time

I'd like to thank everyone for the responses, and also fix the broken video link.

Here it is starting in the rain: https://*******/F325
(link working now!) Starts and runs normal.

Here it is starting (at the supermarket parking lot) in the wet: https://*******/0nkb
All sputtery (at 1:08 and 2:00)


If the problem was wetness or moisture interfering with spark/AFM/etc, then the car would not start in the rain. The problem shows up after driving for a short time and arriving at a local destination. I slow down, or stop the car, and the roughness happens, sometimes to the point where the car stalls and cannot be restarted.

But when I return to the car, an hour later or so, it will start up normally and I can drive it home.

That is what makes this puzzling.


I did take off the distributor cap and cleaned it with some rubbing alcohol. But even before cleaning it looked fine.


Before


After

mrgreenjeans

actually, to me it looks like that top photo is showing at least several 'carbon tracking' marks leading to several of the terminals or contacts.
Change it and the rotor ( don't forget to locktite the set screw in place ) and I believe you will notice a significant change. If the wires are doing the same bleeding off of current as what this cap may well be, the combination of the two may be a source of ignition loss and rough running.

If you open the hood while engine is running in a completely dark area, failed wiring to your plugs will glow in the dark like lightning strikes.... have you looked and checked this ?

What about that main coil wire ? Is it rubbing the headlight arm which rotates and has chafed it ? There is supposed to be a plastic tie holder which is usually missing, that keeps that wire positioned in such a way (straight down and not off to the side) so as to not get 'grabbed' by the headlight arm when lights are switched on.

Check the j-boot as well for tears or loose connections leading to the afm, as noted in post 8.

944Time

>What about that main coil wire ?

The coil seems to be protected from water. I took off the coil wire going to the distributor cap and it was nice and clean.

It looks like I will have to remove the coil to remove the plastic cap covering the top of the coil (or does it snap off?) so I can check the connection there.

It was lightly raining tonight so I drove around to try to get it to act up, but it ran fine.

mrgreenjeans

Yes, what about it ? Is it chafed or does it have some cuts in it from contacting that arm I am referring to ? If it does, you have loss of current. Open the hood in the dark and watch for a light show while running...... possibly this main wire may even be contacting the headlight arm and causing the intermittent firing because it's shorting against it.

DO NOT grab any of the wiring while it's running or you will find yourself about 30 feet back in a nano second with your heart beating 300 per minute. Or stopped.

944Time

If the problem was the coil wire shorting to ground, it would happen all the time.

Since, it only happens under certain circumstances, I think I can eliminate coil wire as a problem.

>Open the hood in the dark and watch for a light show while running

I would have to drive an hour to find 'dark'.

odonnell

One time when it was relatively dark but not quite dark enough, I just opened the hood and draped a blanket over it to block out the light, like when you made forts as a kid. Worked fine (I was using a timing light, which was hard to see as well).

Humboldtgrin

When you realize I told you the what's the problem and you actually listen and replace your coil itself, your car should be fine after that. So REPLACE YOU COIL! Good talk.