3.2L Carrera Intermittent Fuel Cutoff Problem

[cjares]

I have a 1988 Carrera Cab with ~45,000 miles. I recently purchased the car (3 months ago). The car was inspected in a prepurchase inspection and in the 45K service and passed with flying colors. I have driven ~1,500 miles with no trouble.

Recently, the car began having an intermittent problem whereby the fuel seems to be cutting off for a split second when I hit a bump. Doesn't seem to matter if the car is at high revs, low revs, warmed up or not. The engine always recovers, but just loses power for a second. Doesn't do it on every bump, but enough to be annoying.

I replaced the DME Relay, which I thought might fix it, but didn't make any difference. My next guess is the fuel pump, but thought I'd see if anyone else has heard of this gremlin?

Thanks

[York]

Are you sure it is fuel, and not spark? Have you checked the ignition coil wires?

[ischmitz]

Any loose GND connections in the engine bay or under the drivers seat or loose wires in the fuse box. Sounds like the Motronic shuts down and restarts.

[DonMo]

It could also be a cold solder joint in the Motronic brain. Very common and mystery conditions are often diagnosed as such.

[mackskibum]

Heck guys, this could be almost any electrical connection. Could be at the fuel pump, fuses, grounds, DME, Cyl head temp sensor, reference sensor, AFM, battery, coil, etc.

We need more info to help you find this. What makes you think it is fuel related? Are you sure its not spark related? Need to diagnose. Do you know if any key components of the system are losing power? If you replaced the DME relay and it had no effect you will need to keep looking.

[dshepp806]

Why don't you give the DME and DME relay a light tap while idling, just to see if you can induce a malfunction? DME relay socket can be a problem, as are the DME solder fractures. Since she's failing while going over bumps, maybe (just maybe) you can induce the failure while tapping, poking, prodding,....grounds, connectors,also.

Maybe that damned fuse panel? light tapping there with an insulated "tapper of your choosing" may reveal something....

Mackskibum is quite accurate in saying this could be a wide range of things.....one thing's for sure,..it sounds connectivity-related.

Best,

Doyle

[rusnak]

hey cjares,
welcome to the PP board. Nice ride!

I follow a general rule when the car suddenly starts acting up. Try checking the obvious and/or easy things first because they are obvious and easy.

Make sure that your battery clamps are clean and tight, and make sure that your battery hold down clamp is tight. Keep an eye on your positive battery cable. Not just the clamp, but clean the cable. 3.2 911s have a mysterious corrosive salt buildup that eventually makes you cut the cable end off, clean the cable, and install a new cable clamp.

Just go through the wire harness, and clean and tighten the grounds in the front trunk, engine intake runner, connections, etc. Invest in a small brass brush and some electric parts cleaner. Since your car sits so much, I would not at all be surprised if it was corrosion build up. Also, don't forget to clean the relays in the front trunk.

[88911coupe]

+1 on what Donmo says, this happened on my '87 cab and it turned out to be a nearly invisible break in the solders on the DME Unit. There are some excellent threads on how to find and repair this. I managed it which means its not that hard.

[jbrinkley]

even money on grounds and bat. connection.
next bet, big air leak like split throttle boot, snapping the afm vane shut momentarily.