Engine running rough & stumbling, Normal after restart 1986 911 Carrera

[Greg Greer]

I cranked my 1986 3.2 Carrera 911 for the first time in about a month. The start up seemed a little rough running, but idle smoothed out. When I got on the road, the engine was down on power and stumbling. I drove it a little ways, got the engine warm, and varied the RPM to see if it would smooth out. It didn't. After returning home and turning the engine off, and then restarting it, the car is running normal again, good idle, and back to feeling strong. Any ideas what might be happening?
Thanks everyone for your of hard won experience, advice, and knowledge.

[Tom]

First, welcome to Carpokes! I had an '85 3.2 back in the day, and currently have an '86 951 that shares the same DME and basic engine management system. I'd probably start by just starting the car frequently for a while to see if it's a recurring intermittent issue, or if it was a one-time thing after sitting. The fact that it 'snapped out of it' when you restarted makes it sounds a bit like an electrical issue -- bad AFM signal, ground, cracked DME solder joint, etc. Most other things don't fix themselves (vacuum leaks, compression problems, bad ignition, etc.), but one non-electrical possibility is that the fuel pressure regulator got stuck and needed to get saturated and have the fuel pump cycle off/on to get unstuck. Really hard to say what happened -- intermittent problems are the worst. If something is going out, you'll know in time though...

[911R]

I also think that it is important to get the better fuel.

The older cars do not like the current ethanol mix. I always got my gas near the lake or at a race track. The older cars like the proper fuel.

Regardless of what Porsche car you have, please keep it full on the tank. You never want an open area in the tank. It keeps the fuel fresher for the carbs/fuel injection. I also blow the bad stuff out which means some hard RPM's after warming the oil temperature as well as the transmission and diff.

It's a Porsche that has an engine and drivetrain made to go fast.