Was fine last night. This morning, it just started sputtering in 1st gear. Put more gas and it was backfiring. Hobbled back home. It didn't seem to want to go over 2500 RMP in 2nd gear.

Idle is real low -- 250 RPM. I can throttle up slowly into the higher RPM's, but it backfires if I try to hit the throttle too fast. Appreciate the help.

J.Michael

 

Sounds like you may have blown your air box. I know, I had to replace mine. Check the seam where the two halves are joined. You should be able to see some separation if the box is blown.

Don
'81 SC

 

Don,
I could be wrong, but I don't think that would be it. I have one of those pop off valves.

J.Michael

 

It may not be your airbox, but it does sound like you're running lean. There are other air leak possibilities like a hose coming loose, the rubber sleeves on the intake runners failing or the oil tank vent lines failing/coming off. Unfortunately, most of the vacuum hoses are around behind the engine where they're hard to see. Is your oil cap on tight?

 

Check your coil and ignition system. Loose wires can cause those symptoms.

The wire came loose on my coil - it blew my muffler tip off with all the backfiring. It's an easy fix so start simple and work your way toward the more complex.

 

Also check your popoff valve. The glue could have cracked or the pin could have wiggled out, causing an unmetered air leak.

 

Check the relay for the O2 sensor computer under the passenger seat. Mine went bad and the car ran like crap. I checked it by making a jumper wire to temporarily eliminate the relay. The car immediately ran fine.

Don
'81SC

 

Thanks for the responses. I've come down with the flu or something and won't be able to check on it til next weekend. I have checked the simple stuff: oil cap, high tension leads (except the left side). I'll check out the plug wires and the airbox. If that doesn't show any result, I'll proceed from there. Will keep you guys posted. Thanks again.

J.Michael
81SC

 

Hah!!! Here's one for the books. There was a bad connection in the lamp over the glovebox. It blew out the 3rd fuse from the rear-most in the fusebox. Guess what? The fuel pressure is affected by this fuse. I fixed the grounded connection in the glovebox light, replaced the fuse and VIOLA!!! She's running fine once more.

Thanks for everybody's help. I hope my folly becomes of some help to others in the future.

J.Michael
81SC

 

My father always told me to start with the least expensive/easiest to repair possibilities first. Then move on down the list until we give up and take it to our Porsche mechanic!

It could be that your timing is off, fuel injectors are clogged, cracked or otherwise bad spark plug(s)and/or distributor cap, vacuum leak, etc. Good luck and let us know what it was.

Rick

 

JM,

I obviously didn't see your latest post before I replied. Those pesky electrical problems are not fun. How did you discover the problem?

Rick

 

Rick,

I had gone over all of the simple stuff and was reading my Bentley manual, the fuel section. There was a part there where it asked to check the relay and fuse. I just opened the cover and saw the blown fuse immediately. I stuck another fuse in there and it got hot in a hurry (in fact, it melted a portion of my thumb). Then I remembered having problems with the light over the glovebox. I insulated some of the exposed wiring and replaced the fuse. In other words, mostly luck.

J.Michael