Grey Guy

Just sold my 928 from Simi Valley, CA. The new owner drove it away yesterday to his home in Spokane. He was pulled over by the CHP because of the blue flames exiting from the exhaust tonight. The new owner called me and told me the story. Prior to being pulled over he had noticed a nondescript smell and fluid leak while filling it up. He continued to Shasta (nearby) and is taking it in to a "German car" mechanic tomorrow. I had the car about 2 1/2 years, put 30k on it and have had it maintained by a shop that handles Porsche's. Any ideas?

mickster

I'm guessing it is happening as he comes off the accelerator as he's engaging the clutch right before he shifts. If it is constant blue flames-that's another story!

Probably dumping fuel (rich mix). Could be MAF; could be a bad cat; could be a bad exhaust gasket. Could be computer.

One of the mechanical folks here will add more.

Grey Guy

Thanks. Our two heads talked about the cat and bad exhaust gasket. I probably didn't want to think about MAF/Computer... Kinda cool though being stopped for being an 75 mph flame thrower.

Grey Guy

To add a bit more. The car over the past two years has had all the belts, hoses, clutch, spark plugs, sp wires, caps and such. It has about 130k on it now. Thanks.

Mongo

What the crap, I have been trying to figure out how to get mine to do that for the longest time.

123quattro

If it's continuously spitting fire I would suspect a bad spark plug not igniting one cylinder. However, that would kill the cat in short order.

A bad catalyst will never make fire come out the tailpipe.

Grey Guy

I'll make sure they check the plugs. Thanks.

John Speake

Were the flames just on the over-run, from highish rpm with throttle closed ?

Grey Guy

The new owner hasn't gotten back to me, but what he was saying last night, the car was running rough with a constant exhaust flame at highway speeds. Sounds like the cats are history.

the flyin' scotsman

Carl Foggarty had the same issue with his superbikes

All show.....not much go.

James Bailey

Sounds like he was running on 4 cylinders...1/2 the ignition system so two cylinders on each bank would have been dumping fuel and air into the exhaust and only his speed may have kept the red hot exhaust from catching the car on fire. Great reason to ALWAYS contact YOUR insurance company ASAP when you sell a car and keep a copy of the bill of sale (stating AS IS) and notify the DMV ,release of liability, that you have sold the car..... The car could easily have been a pile of cinders on the side of the road. The smell when he stopped for fuel was probably overheated undercoating. I wonder where he would be now if the CHP had not stopped him ??? Generally speaking if a car is running rough it is best to find out WHY ! Before it becomes a much bigger problem.

Grey Guy

Your mechanical analysis defintely seems plausible. And your administrative analysis is absolutely correct. Thanks.

RET

I hope that this does not constitute an attempt at hijacking this thread, but what is the likely cause of a short after fire that happens during acceleration in the following sequence: high RPM and WOT in lower gear, clutch depressed and throttle quickly closed completely? This results in what seems to be a single pop and exhaust flame, but any slight pressure on the throttle pedal will prevent this from happening, so the problem is easily avoided.

dprantl

On a stock LH 928, a bad throttle position switch.

Dan
'91 928GT S/C 475hp/460lb.ft

Speedtoys

..since you opened the door, here's the follow up question.

What in a non stock LH would do/cause it?