1986 Porsche 928S idles erratic after few minutes and bad performance


Asked by May 29, 2012 at 08:09 PM about the 1986 Porsche 928

Question type: Maintenance & Repair

My 1986 928S was just brought over from Colorado to Florida. The PPI was good, the seller said it was running great in COLORADO. It starts ok, but after a few minutes it start to idle erratic and almost dies, then it drives like it is pulling a boat. After it stalls, it is very hard to start, but eventually it starts after 5 minutes. And the cycle continues. Please help!

8 Answers


check the Fuel Pressure Regulator

2 people found this helpful.

mass air flow meter could be bad,and at colorado altitude may have not caused a problem, easy way to figure it out, is to unplug it and run the car in limp home mode the mass meter is under the lower section of the air filter box also check the exhaust flow at the tail pipe the catalytic converter could be restricted and as the car warms up it becomes harder for the car to perform. that pulling a boat sensation , a digital infra red thermometer should show you a temp read before and after the cat, no difference no problem goog luck

1 people found this helpful.

Hi Mike, Thanks for the reply. Now the car wont start at all, after letting the car sit for three weeks. Going from bad to worse. Battery is new, and plenty of fuel and spark. Relays changed, it wants to start with starter fluid, but never catches on. ah the joys of owning a 928, nothing like it. My 911 nevre let me down. PLease let me know any other suggestion why it wont start now. Thanks.

3 people found this helpful.

Do the mass air meter disconnect see if it start and get back to me I have a 83 84 and 86 maybe I can help you get it rubbing


Hi Mike, I will remove the airbox and unplug the MAF, and hopefuly it can start. I will let you know tomorow what happens. Thanks again. Tony

1 people found this helpful.

Hi Mike, OK. This morning I charged the battery some more, and it was 100%. I put it in, and decided to give it another crank with some starter fluid. She immediately started, idled fine and I took her for a long drive.. performance is still not 100%. Here are the driving test results: 1) at low RPM she hesitates and sputters a bit while accelerating from 2000rpm 2) at 50 RPM she shifts hard and goes like a bat out of hell, no hesitation, all the way to 120 plus. 3) when I come to a stop, the idle is very low and she acts erratic, until I slowly give it gas to accelerate carefully, otherwise she will choke and die. It sounds like a tune up issue, maybe plugs, wires, pump, filter, etc. Have you experienced this with your 928 when out of tune? I have not tried the MAF diconnect since I could not see how hard it would be to get to the connector. Please let me know what you think. Thanks again Tony

2 people found this helpful.

Somebody please read this and respond with the fix, because I have the exact same car and it is doing exactly the same thing.

3 people found this helpful.

dido, I have '82 with exactly the same issue as well. I have to unplug the maf to get it to start.

2 people found this helpful.

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