On four occassions over the last two weeks the following has happened: I'll be driving along on a highway at 60-70 mph. I'll get off the highway and onto an offramp and slow to 20-30 mph. My engine then cuts out without warning. To clarify, I haven't stopped the car, I've only slowed from 60-70 to 20-30 mph. Does anyone know what the problem is?

Thanks.

 

Desperate bump.

 

DME relay could cause it - try changing that.

 

Jon,

Are you slowing with the clutch in or out?
I had a faulty O2 sensor that caused similar problems.

 

Dear Jon,
I am sure this exact problem has been posted before otherwise I have been looking into the future.
The most common cause of this problem is a lack of electrical power. I advise that you check first,
Battery voltage with and without engine running.
Battery capacity
Ignition switch
DME relay would be last on my list at this time.
I would not check anything else until all above have been checked 100% serviceable. It may be your alternator not charging the battery and the loss of rpm drops you below 12V and poof all is gone. I have had the problem on the Audi, battery and on the C4, ignition switch. In fact my key ring was too heavy.
Ciao,
Adrian
964C4

 

Thanks everyone! I'll let you know the result.

 

Hello, I am a new member of this forum and I own a 91 964C2 since 1 year and half.

I have a very similar problem with my car, could you explain how you resolved it.

Thanks,
Vincent

 

Dear Vincent,
Firstly welcome to the 964 forum.
Please explain your problem exactly as it happens. You posted oin this fault and another. They are quite different faults. Please provide as best as you can a full and accurate description.
Please include all details like "it only happens when it rains" or "only when the engine is cold". Whatever the symptoms are plus any warn lights that may come on.
964s eat batteries so I would advise you check your battery first and foremost. 12.4V with engine off and 13.8V min when engine is at idle.
Ciao,
Adrian
964C4

 

Hello Adrian and thanks for you reactivity.

First of all, I would like to precise that the following electrical parts have been changed recently:

- Battery (12 months)
- Distributor (6 months)
- Spark plugs (6 months)
- Ignition Coils (6 months)

Secondly, the engine always start very easily whatever the temperature or humidity is and whatever it is cold or hot.

In fact, I've got only 2 times the problem with my car:

The first time, it was 1 month (and ~500kms) ago. I was on a racetrack with some friends for the day and the engine was working very well. The weather was dry and the temperature was around 10°C.
After a 30mins break, I decided to go for a new run. As soon as I exited the pits, the engine stopped while I was accelerating in 2nd gear.
I parked my car near the grass and after 3 or 4 tries (the starter worked), the engine started again and worked well again immediatly.

The second time, it was yesterday (7°c - dry): I haven't used my car for 1 week and it started without problem like every time.
After 3mins and 300meters, the engine stopped while I was accelerating, very smoothly, in 2nd gear. I parked the car and tried to start it again but it didn't work (starter was working but no ignition) immediatly.
After 5mins and several tries it started again. At the beginning, it seems to me, that the engine didn't go very easily into the revs.
Went back into my garage, I stopped the engine, removed the DME relay and put it back. I started the car and immediatly the engine worked well.

I hope that this explanation, in my bad english, is clear enough and thanks in advance for you answer.

Vincent

 

Dear Vincent,
This kind of smooth cut out is exactly that a cut out. Power is being removed from the DME and the fuel pump. I would suspect the contacts of the relay. I would advise you check the part number of relay R41 and if it is a 944 number replace it.
Problems on the track are basically caused by overheating. You are working things really hard.
I am sure your problem lies in the fuel pump circuit.
Ciao,
Adrian
964C4

 

Thanks Adrian.

At this time, the DME R41 relay is a 944 ... part number.
I will buy a new one next week.

Vincent

 

Hey guys,

definitely go thru the steps Adrian listed, but here's one more thing to look out for: I had a simliar problem this past summer, after checking the DME, battery etc, and also changing that 944 part number relay to a 993 part - I learned that the problem was with a loose connection behind my airbox. There was a bulletin about it years ago, so its a possibility until the wires get clamped down better. Just one more thing to check! Good luck!

 

Any idea on the contents of the bulletin and the location of the terminals you describe?

 

Dear Youcef,
You remove the air box cover and filter. You then remove the air flow sensor connector and look for a black dot (if I remember correctly). If you have a black dot painted on the connector it has been modified already. If no black dot you get better access to the connector and pull it apart.
follow the TSB instructions,
Ciao,
Adrian
964C4

Air Flow Meter Cover Causing Erratic Idle, Loss of Power
90porsche08
May 15, 1990
Subject: Engine, Inconsistent Performance

Models Affected: 911 Carrera 2 and 911 Carrera 4, Model Years 1989 (K) and 1990 (L)

Concern: Inconsistent acceleration, erratic idle, loss of power or engine dies.

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.
Work Procedure: 1. Remove air filter housing cover and filter.

2. Push down locking spring on air flow meter wiring plug and disconnect plug.

3. To gain access to plug, pull wiring harness with plug between air flow meter and idle stabilizer towards rear of vehicle.

4. Pull back rubber boot and cut protective wire covering using side cutter or similar tool.

5. Heat protective wire covering with hot air blower to maximum 110~ C (230~ F). Pull off and discard protective wire covering

6. Reinstall rubber boot on plug housing. Loop wiring harness along side of plug and tie wrap.

7. Reconnect wiring plug. Make sure spring lock is engaged.

Important: Do not use contact spray.

Work Procedure:
8. Check clearance between wiring harness and vent hoses.
(continued) Distance should be at least 15 mm. If necessary, bend bracket
on right shock absorber mounting slightly forward Make sure vent hoses are properly installed on bracket at shock absorber mounting and on bracket in front of air flow meter. The small diameter hose must be routed below the large diameter hose,

9. Reinstall air filter and filter housing cover.

10. Mark air flow meter with a black paint dot.
Parts Information: Tie wrap: PN 999 513 021 40

 

Jon,

I had a sort of problem last spring. After starting the engine, drove away, and by taking the first exit or traffic light, used the clutch......and off was the engine......

It was the green connector which leads to the knock sensor. You have two of them, on in the middle on top of the engine [green] and one behind the engine blower fan left in the engine bay.

Disconnect them, clean them with contact cleaner and protect them with a electrical grease. Then reset your DME and let the car idle for 20 minutes.

You could at least try this. I never had the problem again.

I also know that if the distributor belt is broken [from ignition distributor] the engine stops running if you go off your gas. Double check that also.

OT: Jon, you live in a beautiful town! I love to come there every now and then, sitting outside Starbucks, have some coffee and just look around what comes by.
Lovely. Lucky bast#%*