1987 924S won't stay running

My car sometimes runs like a dream and then abruptly will lose power, act like it’s not getting fuel, not respond to the accelerator and sputter and buck. My mechanic has rebuilt the fuel pump, cleaned fuel filter, cleaned out tank, replaced hoses. He’s familiar with Porsche engines and I know he’s not blowing smoke up my nose, so to speak. He’s tried everything he can think of. I never know when it’s going to act up. It will run smoothly, I will drive it hard, drive it slow and easy, corner hard, not hard, and it sometimes stays happy, sometimes decides it doesn’t want to run. It improves when clutch is pushed in, acts like it wants to respond, then after I let the clutch out and apply gas, it starts to buck and there’s no power. Haven’t been able to get it out of first when it does that.

If the entire fuel system has been checked out then the next order of business is to check out the ignition system. The coil could be breaking down under temperature or you may have something as simple as a cracked distributor cap. I would move the 924 into a very dark garage or wait until nightfall. Start the engine then watch for fireworks. You might get lucky.

Have you posted this on Porsche forums?

TX: yes, I have. I’ve also read through many of the similar posts on those forums. Everyone has a different opinion! This is my first time for trying car talk; I actually tried to call them yesterday. Do you own an older Porsche?

I’ve relayed the above info to my mechanic and he said he’d checked those already.

Thanks everyone,

No more car talk, they’re retired. No, I don’t own a Porsche, but always thought the 944 would be a blast!

Any guess is as good as any other but it would still be a guess.

I’d start instrumenting the car:
A good way to start is to mount a semi permanent fuel pressure gauge and make it so you can read it from the driver’s position. Maybe snake the line out through a vent and mount it in front of the windshield so you can look at it. They are cheap and you can probably rig (duck tape is our friend) it to a magnet that ou can sit on the hood. It will look odd, a meter sticking out in front of windshield that’s sitting on the hood but you may get a nod from street racers.
Drive it around, see where the needle wants to be when it drives well and then, when it starting to stutter, see whether the needle changed appreciably. Too little or too much pressure can make that car do weird things.
If nothing happens to that fuel pressure when it stutters, you know it isn’t the fuel system and so you can move on to the ignition.

TX: this car is a 944 engine in the smaller, more streamlined 924 body. It’s FUN! And the smoothest car I’ve ever owned or driven. Sweet, sweet, sweet.

The culprit was the throttle adjustment valve. It had been replaced then apparently went south. As of yesterday, she’s driving like a dream. WheeeeeeeEEEEEEEEEEEEEE!!!