Engine cutting out!

[91C2wrencher]

Just yesterday I had a unexpected hiccup from my 964's engine. Today I took it out and within a few hundred feet I knew I had a Problem. The engine just plain cuts out and check engine light(duh) comes on. It did it once while I was back in the driveway with rear lid open and I swear I heard a distinct electrical snap right before it cut out. Any ideas where to start?

[Britwrench]

Have you had the spark plugs out?

Check the plug wires are on correctly.

Had the valve covers off?

Check you haven't trapped the 02 sensor wire under the upper valve cover.

Check all the wiring connectors and make sure the distributor belt hasn't broken.

Check engine lights are usually caused by and ignition related problem. Could be a direct short to ground through a plug wire
or connector.

[FRED/LI]

My 90 would die at odd times...like on the Long Island Expressway at speed. Pull over and restart. Turned out to be the DME relay in the fuse compartment. Original unit has been superseded.

[91C2wrencher]

thanx, Fred I've ordered a new DME. I've seen this posted as a cause for many troublesome antics, so I'll try a new one and post the outcome.

[turolla]

Is this a Turbo? I had a similar problem caused by the fuel pumps relay cutting out. I used ajumper wire and the pumps worked, so it was the power to the relay. I found that I had a problem suppling voltage to the + from the Turbo control unit and later found that the ground was bad too. Solution direct wire relay to a different keyed power source and grounded directly to the frame. Why can't they make these things SIMPLE!!

[911wings]

i hate to tell you this but mine started up on fri, it's the disributer, you have to get an new one, or a new belt

[MonkeyBoy]

Also check to make sure that the mass airflow sensor mod has been done. There is a technical service bulletin about this that you might be able to dig up.

[flolds]

I had a similar problem on my '90 C2 and it turned out to be the ground on the cylinder head temp sensor. The car died or lost significant power several times on a long trip. It would restart and run fine after a "rest" of less than 1 hour only to begin the problem again within an hour.

[Bill Wagner]

C2Wrencher:

I wouldn't replace a DME without confirming the cause of the problem. The DME is probably one of THE most reliable parts in the car since it's solid state. The cabling/wiring running between the DME and the various sensors is another matter all together...connectors tend to oxidize with age.

I would spend more time troubleshooting it first, or if possible borrow a DME from someone else and swap it in to see if it makes a difference. I would also DECODE the output from your check engine light (if your car is new enough, you can get the DME to spit out the codes that are probably identifying the most likely culprit...otherwise you need a Bosch Hammer for the job but most shops will do this for either free or a very low cost).

The type of problem you're describing can be caused by a lot of things.

Good Luck,

Bill Wagner

[91C2wrencher]

Well boys. I had my local wrench solve the problem, I hope! He first noticed that I had two spark plugs that were "falling out" causing irratic discharges and upseting the DME unit, seems odd but it could happen. after tightening them up he couldn't get the intermittant cutting out to happen again. I had put in the new DME relay(it is a beefier looking unit) with no success. Point of interest, I checked the flashing "check engine" light code and it came up as a failed idle switch, I checked the switch and it was fine. So the cars in the shop getting the power steering cam shaft seal replaced, a valve adjustment job. My wrench made a point of mentioning how clean the valve train is on my car, testiment to Mobil 1 I'd guess.