interrupts/stalls in acceleration (3.2 carrera '86)

I just bought a '86 911 carrera and didn't notice this problem in the test drive. When you accelerate fast it will make shocking interupts. This really worries me. The Porsche dealer thought it was the easiest to try cleaner in the gasoline and I did. It did not work. Right now he says there could be many causes, the one even more expensive than the other. He claims to have a list of 27 points to check and I think he wants to cash his retirement from my problem. Is there anybody that has an idea of what it could be. Advice would be appreciated.

Fuel filter is an inexpensive place to start.

As you just bought the car, I personally would start with a full tuneup, that's what I generally do whenever I get a used car. All fluids, filters, plugs, cap, rotor,valve adjust, etc. etc.
While doing that, I'd visually inpect all the connections, including the spark plug connections and cables. Check these with an ohmmeter for proper resistance.
If you do all those things, I think chances are good your problem will be fixed! If not, you will have at least eliminated them as problems and can move on with your diagnosis.
Finally, you may want to check/replace your cylinder head temp sensor. It is a known problem on the mid 80's Carerras, and in fact I think there is a factory updated part. Again, if I bought a mid-80's Carerra, I would change this part to the updated part as a matter of course. Its only about $15. (sorry, don't have the part # memorized or handy).

I would also look at the DME relay and the connection of the DME unit itself. Fuel filter is likely OK since the car runs OK at all other times. Check the fuel pump relay as well, the coil, and follow the above listed issues for a tune-up of a used car. It's probably something small.

Also...are you sure you're not hitting the redline and bumping the rev limiter?

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Mark Szabo
1986 911 Targa 3.2

It happened to mine not long after I bought it. BTW, mine is '87. First, the car hesitated on the freeway. Then, it developed to stall and could not start. Changed the fuel filter, fuel pump and relay. Did not work. I was getting frustrated. One time, friend of mine accientally tapped the DME connector and the car started. So, for sure is the DME, but could be the connector or the unit itself. I took the DME apart (not suggested) and found nothing lose in there. Next move, I wrapped the whole thing w/ the connector w/ duct tape tightly. It worked and kept driving it for a while until the racing season started this year. I took it to my mechanic and had the Borch specialist repair it. I had no problem ever after.
Hope this help.
Andy

I had the same problem with my 90 C4. I noticed that there were two micro switches triggered by the throttle and gave them both a squirt of WD40. Not sure if it was purely coincidental, but the problem is no longer evident.

Thanks. Where is the DME unit located? I still need to get me a service manual. It is starting to hesitate (stuttering) more now. It starts really well though but the stuttering is rather unpredictable. First it was with fast acceleration above the 4k revs but now it happens with 3k revs on steady driving. Can it stall not to start ever after? Somebody told me it could be the vacuum hose...Could it? Thanks again.

Originally posted by andyu911:
It happened to mine not long after I bought it. BTW, mine is '87. First, the car hesitated on the freeway. Then, it developed to stall and could not start. Changed the fuel filter, fuel pump and relay. Did not work. I was getting frustrated. One time, friend of mine accientally tapped the DME connector and the car started. So, for sure is the DME, but could be the connector or the unit itself. I took the DME apart (not suggested) and found nothing lose in there. Next move, I wrapped the whole thing w/ the connector w/ duct tape tightly. It worked and kept driving it for a while until the racing season started this year. I took it to my mechanic and had the Borch specialist repair it. I had no problem ever after.
Hope this help.
Andy

It's under the driver's seat. Remove the seat, and disconnect the negative battery terminal. The DME is the box located on the side nearest the tunnel with the large cable connector attached.

Remove the connector. You might want to pull the DME out and open it up, check the connector for anything on the contacts. Depending on your connector you might be able to clean part of it with a pencil eraser.

Also pull the DME relay and make sure its contacts are clean. It's the little square doohickey in the socket next to the DME itself.

Good luck!

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Mark Szabo
1986 911 Targa 3.2

My car stalled or stuttered no matter at what rpm. Very often, I had hard time to start it again. If it's the vacuum leak, you may have problem even at idling.
Andy

Isn't there a list with troubleshooting facts around in which the stuttering problem is threated in order of most likely causes?

Originally posted by andyu911:
My car stalled or stuttered no matter at what rpm. Very often, I had hard time to start it again. If it's the vacuum leak, you may have problem even at idling.
Andy

I see some very good advice and ideas above. Some specific parts (DME commector, relayl temp sensor, etc.) are suspect.

But I just want to say that Jim T's advice is the same as mine. EVERY TIME a car misses for me, I'm likely to replace the distributor cap and rotor, probably spark plugs, and reset the mixture. Checking ALL electrical connections is time well spent. I'm not going to restate what Jim T said, because his explanation of what, and why, is perfect.

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'83 SC

I total agreed with their advice, too. Start it simple. I have done all of the above myself before I spent money to have a mechanic to check on it. However, the first mechanic only said I had a bad DME relay. Changed. Still had the same problem. I went to the other one and finally found the REAL problem. Replacing the parts in the process gave me peace of mind also. I have search through the site here, manuels and posted it here about the stutter problem. I had no luck with the advice and had to go all the way to the DME. I guess mine was the worst case.
Andy

Thanks I will do just that. Could you help me in finding the part number. The 911 is a 87 model (with G50 etc) Thanks!

Originally posted by Jim T:
As you just bought the car, I personally would start with a full tuneup, that's what I generally do whenever I get a used car. All fluids, filters, plugs, cap, rotor,valve adjust, etc. etc.
While doing that, I'd visually inpect all the connections, including the spark plug connections and cables. Check these with an ohmmeter for proper resistance.
If you do all those things, I think chances are good your problem will be fixed! If not, you will have at least eliminated them as problems and can move on with your diagnosis.
Finally, you may want to check/replace your cylinder head temp sensor. It is a known problem on the mid 80's Carerras, and in fact I think there is a factory updated part. Again, if I bought a mid-80's Carerra, I would change this part to the updated part as a matter of course. Its only about $15. (sorry, don't have the part # memorized or handy).

If the part you're looking for is the head temp sensor--I believe the latest P/N is
930 606 915 00 (replacing previous P/N 911 606 405 00) this is for 84-89. The part is not $15 as stated in an earlier post but about $70.
Also see Pelican Parts tech article: "Cylinder Head Temperature sensor upgrade". I believe the P/N referenced in the tech article has been superceded by the part No I referenced above.
It's not necessary to remove the seat to access the DME box - Just move the seat all the way back - worked for me.
Charlie '87 Carrera

[This message has been edited by Charlie Moore (edited 10-18-2000).]