Running issue stumper of the week
 

You guys are insanely informed, which is why I love this forum. Looking for any input to help out here.

Yesterday, perfect weather in the 60's, drove my 85 911 3.2 widebody w/ 64k miles and freshish tune for 6 hours, 90% highway. Car performed perfectly, started and idled and pulled like a train every time it was asked.

At the very end of the trip (thankfully 5 miles from home!) it began 'hiccupping' at speed. Meaning, it 'skipped' very quickly... on power, no power, on power, no power, then it'd 'catch' and continue for a bit, and do it again.

Made it home w/o getting stranded. This morning, started like a champ, idled, ran 10 miles to my office without one single problem of any kind.

Questions:
1) Do fuel pump relays 'start' to go bad? Or are the all or nothing?
2) Could trash in fuel pick up have caused it? Car was low on fuel when I started my journey, filled up a few miles later, seemed fine.

Any input or long distance diagnosis out there? Really appreciate it in advance.

I'd start by switching out the DME relay, if that's not it you need a spare anyway.

That is a stumper. Fuel is usually an all or nothing issue. Sounds like it may have been some sort of electrical connection or component that was overheated from the long drive.

Old spark plug wires would do something similar.

What kind of driving were you doing when it started sputtering?

Do yourself a favor... start the car... pop the hood... remove fuse cover... wiggle the fuel pump relay... had a similar issue on the '83 SC and it was a poor connection on the fuel pump relay.

If that is not it, then also check all grounds/connections... sounds like electrical problem...

I do have to mention... I had another issue with the '83 SC and it turned out to be the distributor. The bottom of it was loose. Had to have it rebuilt. Darn thing would take out the coil...

Great suggestion, and I'm now so DME paranoid, I carry one anyway. The one in the car only has maybe 300 miles/6 months on it.

Does seem like it. Am perusing engine compartment and fuse box for clues.

Plug wires are new (year ish old), but you make me wonder if one got or is getting loose. Gonna check.

Driving was pure highway, up and down the gears, and at the exact moment of the infraction, was doing maybe 65 or so, 5th gear. Nothing fancy.

Going to do the FP Relay thing. Good idea. When the engine was out, I actually detailed, cleaned up all the connectors in this area but easily could've bent a prong.

Thank you all for your suggestions and support. Love the RL!

Take a close look at the fuel pump wire crimps, fuse/holder, prone to overheating, holder looses its "springiness".

Also, WEIRD things begin to happen when/if the battery is being over charged.

Another common occurrance.

Wachuko, FYI, the DME relay for the 84-89 Carrera 3.2's are under the drivers seat attached to a corner of the DME ECU mounting studs, not under hood or trunk.

84-89!! I am thinking of my cars... 81-83 - Sorry OP!!!

Thank you Ron.

No problem. I have episodes like that occasionally.

Hey, I think you edited your post to say Fuel Pump relay, not DME relay by the time I saw it, so no harm done.

I live in an episode like that. Many are re-runs.

mine was coil the .. cut in and out totally random. under load not underload.

Interesting. I kept hearing how the German-built Bosch coils were superior to the others (Mexico? Can't remember) and my new one came from the 'other' place.

Given that the car was very tired and decently warm after 5 ish hours of driving by that point, a heat-related coil interference makes sense. Guess I'll get Santa to bring me a quality coil.

BTW, I have other faster, more capable road cars than the 911, but the fun factor, the sheer driver-involved feeling of the car was absolutely serene. I had flirted with selling the car, but there is nothing I could replace it with that brings that kind of smile.

Much of the joy comes from communicating with other enthusiasts like you folks. Thanks.

Here's a suggestion that some of you may find a bit weird and I have to confess that I don't understand it fully myself. However, a few years ago at a track day I had a problem where the engine would cut out under hard cornering when turning right - not left, only right. As you can imagine, I checked all sorts of things like connections, wires, etc. And I spoke to a few mechanics, one of whom is an older gentleman who has forgotten more things about engines than most of us will ever know (although he actually has a great memory). His suggestion led me to insulate the coil body from the mounting bracket with a couple of layers of electrical tape, based on the assumption that the paint of the MSD Blaster coil had worn away over time. This solved the problem beautifully and it has been fine ever since. Maybe it would work for your problem and it's a free fix.