BimPorDoug

Today I installed a rebuilt CD ignition box in my CIS 911. This is the first time I've started the car in 7 months. I store it every year. This year I had the CD box redone. The car takes for our five tries to start. This year was like many others. I installed the batteries (after putting in the ignition box) check the actuation of the pedals and hand throttle and crank. The car went through it's annual wake-up shenanigans and I got it running. I pull out of the garage and all is normal. The car ran for about 8 - 10 minutes at about 2,000 rpm. I started doing some work on putting a new registration sticker on my lic plate and the idle breaks up and the car stalls - almost as if it ran out of gas. I restart it and it won't run below about 3,000 rpm. I hear all kinds of pops coming out of the engine. I pull the air cleaner cover and the perimeter of the pop-off valve is melted. The inside of the airbox above the pop valve is charred. I've had the pop valve blow out of the airbox but never burn like this. The rubbers are OK and I've replaced the seals at the injectors.

Could a newly rebuilt but failing CD ignition box do this? Any other thoughts? WUR? The car is on its third fuel pump and it has maybe 12,000 miles on it. The car has 111k on it. It runs great - until now. I'm taking it to my favorite Porsche indie this week via flatbed to try and figure this out.

J richard

I would look carefully at the air box and make sure you haven't split it. The pop off is a safety valve but you can still blow up the box with one installed...

theiceman

sounds like you are having massive backfiring throught the intake and it is burning your pop of valve. even the thing you bought to protect your air box could be leaking and allowing a lean condition. Defintiely a CD box could cause this with cis as if it is not burning there is exces fuel that can ignite when another cyliner fires..

BimPorDoug

I'll take a careful look at the airbox. Funny that the engine would just die once it warmed up. Perhaps when the cold start injector shut down it contributed to a lean condition. The CD box would contribute to an ignition timing issue if it malfunctioned. I had Bosch box rebuild which only triggers once, unlike the MSD variety that continuously sparks. I should know in a week or so once my indie shop has a chance to look at it more carefully.