Mark Beaudouin

I have a 1989 964 C4 with 70K miles. I've owned it for two years and the car has generally been fine. Occasionally, however, the following problem occurs: when pulling out onto a road from, say, a stop sign, I will release the clutch and begin to accelerate only to have the car begin to immediately lose power, sputter and stall. It starts up again right away, but when I release the clutch and begin to drive it does the same thing - loses power, sputters and stalls. After a few of these, (generally two), the car then starts and works fine again. The only thing I can think of is perhaps when this occurs, the car isn't warmed up enough - but when it happened the other day I had been driving for 15-20 minutes and then parked the car for an hour and then started it up again and thats when this random deceleration and stalling happened.

Any ideas as to what could be causing this?

JonSeigel

I have the exact same problem. It happened again just yesterday. It only happens when the engine is warm; it has never happened when the engine was cold. I've been told it is the fuel pump. Since it happens only occasionally, I haven't done anything yet. However, I too would be interested in input from others.

BTW, maybe the post should not be called "'89 C4 random stalling" because I have a '93 C2. So it wasn't something Porsche worked out during 964 production.

Mark Beaudouin

Jon: I just searched "fuel pump" on the forum and came up with a variety of posts. One called "total muscle failure" is rather long but seems to deal with the issue we are both confronted with. His car is in Singapore and after two trips to the shop the problem seems tohave been a "fuel idle switch" I think it was called.

My car acted this way a few times about 9 months ago, and then did it again this past weekend. In between its been fine. Anyway, check out that other posting to see if there are any similarities to your situation. The three common themes seem to be 1) dying fuel pump, 2)bad coil and 3) fuel idle switch.

Randall G.

Have you guys replaced your DME relay? This relay actually powers both your fuel pump and DME, and can causes symptoms similar to what you're experiencing.

Cheap (less than $20) and easy installation.

Best of luck!

JonSeigel

Randall:

If it were the DME relay, would the stalling be limited to the specific situation I mentioned (engine hot, engine dies only when clutch released after stopping, after engine dies it turns over and immediately crashes, after a few attepts it will turn over and not crash, etc.)?

In any event, I have a spare DME relay which I did not install because there was nothing wrong (that I knew of) with my current relay (which I presume is the original because it has a 944 part number. Come to think of it, my spare relay has a 993 part number). But I'll swap 'em tonight.

Randall G.

Hey Jon,

From what I know of DME relay induced problems (which isn't a lot ), the symptoms can be erratic, inexact and irregular. I've also read that the first thing to look at when experiencing stalling/hard-starting problems is the DME relay. Suppose it helps that it's so cheap and easy to install.

Randall G.

An interesting thread on the DME relay:

<a href="http://forums.rennlist.com/forums/ultimatebb.php?ubb=get_topic&f=3&t=000561" target="_blank">DME Relay Thread</a>

Robert Coats

[quote]Originally posted by Randall G.:
<strong>I've also read that the first thing to look at when experiencing stalling/hard-starting problems is the DME relay.</strong><hr></blockquote>

Had "turns over but won't start" problems with my '91 C4, and after some VERY helpful troubleshooting with Adrian, we determined the DME relay was bad. $18 for a new one, and two months later, and the problem has never come back.

The original DEM relay had a crimped case, but the new-style is fully potted (sealed) and looks to be more robust.

For $18, and literaly 60 seconds to swap it out, I'd give it a try.

Christer

Jon Seigel

If your problem occurs only when the engine is warm then it is unlikely to be the fuel pump itself. As far as I am aware, the fuel pump works whether the engine is hot or cold so I would go with RG and guess the DME relay.

Touch wood, I haven't had a problem with the DME relay yet - although it seems very common...

Wsp964

I've got the same probs at the mom ... have a look at my thread "gastank iddle probs".

For what's it's worth :

I was told to swap the DME relay to begin with, if that does not help than :

- check fuel injector relay
- check fuel injector, maybe clogged
- bad coil
- check fuel filter, maybe junk/water in the gastank
- possible air leaks
- check iddle control valve
- check distributor + the distributors caps
- fuel pump

This advice came from Adrian, Ade, DaveK and all the other helpfull guys .... I happen to be the worst mechanic in the universe

Let us know what solved your problem please ... maybe you can help me too


Thanks

WSP964 <img src="graemlins/wave.gif" border="0" alt="[byebye]" />

MonkeyBoy

There was a technical service bulletin about an update that needed to be done on early C2s and C4s. Check to see if this was done first. You can get the full details from a dealer or <a href="http://www.alldata.com/TSB/50/90504812.html," target="_blank">http://www.alldata.com/TSB/50/90504812.html,</a> but it's very easy to do yourself (not sure why they recommend doing it once the engine is out). All you need to do is remove the air filter cover, unplug the harness, remove the harness cover, and use a tie wrap to fasten the cable back to itself so that it stays out of harm's way.

Air Flow Meter Cover Causing Erratic Idle, Loss of Power Technical Service Bulletin

In part, this is what is says:

Possible Cause: The air flow meter wiring harness protective cover contacts the engine ventilation hoses causing current flow interruptions on the plug terminals.

Vehicle Information: The protective cover on the air flow meter wiring harness plug was discontinued from production date February 13, 1990. VIN's 96 - LS 45 1659 Coupe 96 - LS 46 0409 Targa 96 - LS 47 1072 Cabriolet

Repair Information: 911 Carrera 2 model year 1990 and 911 Carrera 4 model years 1989 and 1990 prior to the above VIN's should be modified when the engine is removed or when working on the air flow meter, even if no engine performance problems are present.

The bottom line is to first look at your air flow meter housing (next to the air filter box on the left), if the fix was completed they should have put a black dot on the housing. Key word here is SHOULD.

They recommend this connector be fixed even if you are not experiencing any problems because it will sooner or later.

The problem is the wires get pulled by an interference with a couple of hoses causing the wires to pull out to the connector just enough to break contact intermittently and causing all of the problems. But when they make full contact again the problem goes away.

JonSeigel

MonkeyBoy:
Thanks for the info. Hopefully, that will assist the original poster, Mark, who has an '89. I, however, have a '93 with a build date during 12/92. I just wanted to make this clear if anyone reviews this thread in the future.

I have swapped DME relays and will see what happens. As I previously mentioned, this is not a constant problem for me. So I cannot tell immediately whether the DME swap has done the trick. However, I will provide an update if the problem persists or has not occurred for sufficient time that I believe it has been solved.