84 944 Engine idle and running erratic
 

I have a problem wth my 1984 944. The problem is, sometimes when I go to start the engine, it will sputter initially but idle and run fine. Other times it will sputter the entire time I have it cranked. It sounds as if it's running on 3 cyliners. I have replaced the O2 sensor, reference marker sensor, speed sensor, thermal switch(from previous problem). After a few days, after the sputtering problem, I can sometimes go back out and start the car and it will run fine once again. Any suggestions on what may be causing this? My next step was going to be calling a priest to perform an exorcism.http://www.pelicanparts.com/ultimate...oads/logo6.gif

Try spark plugs and wires. Worked for me. Are you sure that the wires are connected to the right plug on the distributor cap?

mde,
Before you get too religious, I had a wierd situation with my O2 sensor and may be worth a look. I was running really rich at times and it turned out to be a grounding issue. Since I had purchased the car, the O2 sensor wires were twist tied together. Knowing that the outer shield was for grounding purposes, I made a connector with thte outer shield tied off to ground on the firewall. This grounded out the demons and have been running smooth ever since.
Regardless, let us know what you find.

sounds like injector prob to me.

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keith
'86 951 redNeckarsulm

I agree. Sounds like the cold start injector. This injector works for a short time until the engine is warmed up. I could also be the ignition system. This system has to work harder when the engine is cold and requires the most voltage when starting. As for grounded wires. This causes more problems then any other automotive challenge. Agood ground at all conecting points is a must.

OK guys.. heres a little more info. Earlier this afternoon I went out to try a start-up. It again sounded like it was on 3 cylinders. Lter on..maybe an hour or so, I went back outside and started it up. It was able to idle this time but when i pressed the gas pedal, its sputtered for a split second, then the RPMs went up normally. It would only sputter at the instant i hit the gas pedal. Now for the really baffling part. I just got back inside and this time it sounded like it was hitting on maybe 2 cylinders. It was missing so bad the the entire car shook. Time for the exorcism yet?

Could the problem be a short in the ignition system? I did have a problem with the wiper switch. It was stuck on the "interval" mode last week. If the wiper was OFF, it would go on the "interval" setting. I wiggled it again and it went into a normal wiping motion. One more wiggle of it and it stopped doing this and was back to normal. Since the ignition is located by the ignition, could a bad ground in this general area be causing all these problems?

also, check your fuel punp volume...

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keith
'86 951 redNeckarsulm

It might be worth trying a new DME relay

Throttle position sensor also.

Thanks for the information fellas. If anyone else out there in Porsche land has any suggestions, I'd love to hear them. I want to get this squared away ASAP. This has been an on-going thing for about a year now. I miss driving that car.

Such an intermittent behavior could certainly be an electrical problem .. definitely try a new Fuel Pump Relay ... $20 at the dealer ...
My car wouldn't start one day, and after 3 days of debugging ... that was the culprit.
E

Check inside your distributor cap for dead criters.

I'm convinced theres an electrical problem. The real pain is finding out where. I believe we had checked all the relays and they were ok. Once when it was in the shop, we pulled the DME out of mine and put it in another 84 944. We took the one out of the other 944 and put it in mine. Both cars worked fine. I did have a Viper alarm system installed but its since been disconnected. I thought the alarm could have been the problem but it was in there for about 2 years before all the problems started. This is mind boggling. The mechanics have said they have never seen anything like this before.

Oh yeah..one more thing. I noticed the smell of gas when I'm trying to start it during the "acting up" stage. Its getting fuel. The fuel pressure test checked out fine. It's not a slipping timing belt. If it was, it would'nt go back into time like it sometimes does. It would'nt start the least time I tried it yesterday. It'll probably start today or tomorrow (whenever I get a chance to try it again).

The fuel pump relay might seem fine, but it takes rigorous testing to find out if it was working ... your best bet is to replace it, and in the worst case scenario, you'll have an extra FP relay lying around ....

E

You, by chance, haven't changed the fuel filter lately... Have you???????

Rich

The fuel filter was one of the first things we changed. It seems like its not getting fuel, but in reality, its getting too much from what the guys at the shop are saying.

dude, i'm telling you - injectors.
get them cleaned... when clogged, they drip - too much fuel in cylinder at startup, etc...

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keith
'86 951 redNeckarsulm

I think we may be onto something here guys. I just went to the shop to have a skull session and we came up with something that had not been checked before. Theres an idle control valve (I think thats the right name for it)that sits on top of the engine just under the intake. That thing regulates air/fuel mixture from the way I remember the mechanic saying. Anyhoo, when you turn the ignition on, it should be active and you should feel a vibration. He showed me what to look for and we checked one out on a 911. I got back here, turned the ignition on and there was nothing. No vibration at all. We checked the injectors before..sorry I didn't mention that before. But the idle control valve does not appear to have any life to it. Heres hoping thats the problem. I'll keep you posted.