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.

oh.

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keith
'86 951 redNeckarsulm

Sorry, I don't think so. There is no idle stabilizer or cold start injector on an 84 944. Idle stabilizers were first used in 85.5. Richard

Well, if that part doesn't exist on the 84 944, what part is it exactly thats sitting under the intake on top of the engine right where my mechanic said the Idle stabilizer would be on the 944? Or is it possible to have the top half of the engine be a 1985 1/2 or higher on the 1984 model 944? Theres something located exactly where the idle stablilizer would be.. Any thoughts?

AAV-Auxilary Air Valve. It supplies extra air durring warm up only. Richard

[This message has been edited by RIchard944 (edited 08-16-2001).]

Richard is right, it is the Aux Air Valve, which helps on cold starts because it lets the extra air in ... look for my previous threads on this issue (AAV) and you'll see what I mean, I had to take mine out and clean, adjust, and test it ...

It has a bimetallic strip that closes as the engine heats up (within 30-60 seconds) ...

Also, there is NO cold start injector or valve, early 944s just have the DME telling the injectors to run rich for the first 12 seconds or so, then it starts listening to the O2 sensor and the other sensors and cuts down on the fuel ...

E

OK...let me step in here for a quick moment. On my 83 my car started to act like yours, drove me crazy. Called the mechanic and he said check the easy stuff first. He told me to check the o-ring on the air by-pass screw which as you all know sits next to the throttle cam. I took it out and well what do you know....that thing was toast. Went to the local hardware store and bought a replacement o-ring for about 12 cents. Put it on the screw, screwed it back in and started the car and well what do you know.....perfect idle. This of course is after I checked EVERYTHING. It eneded up being a 12 cent part and took 5 minutes to fix. Such is life with a Porsche 944. http://www.pelicanparts.com/ultimate/smile.gif
Mouse

Yeah.. I heard of stories where one tiny electrical connectorwas bad.. After hours of diagnosis, it turned out the part needed was maybe 25 cents. Parts- .25 Labor- $300 after all the checks were done. Hitlers Revenge.

Plugs wire cap and rotor should fix the problem

OK guys.. I went to take it to the shop today. I went out this morning, it started right off the bat. Running fine (so I thought)for about 2 miles or so. After it got nice and warmed up it crapped out again. Took it to the shop and looked at a few things, checked to see if its getting fuel, losing spark, etc.. All of that tested out fine. After the engine had cooled, we had the fuel pressure guage on it and it started and ran fine for about 15 min or so when we shut it down. Is this sounding like a AAV fault. When we tried to start it after arriving at the shop via tow truck, there was an odor of gas. But after the engine had cooled, it started and ran fine once again.