Q — In spring of 07 I traded my boat for an 88 930 slant nose coupe from Arizona. For the first couple months, I had no problems. Then leaving work one day, it would not start. After 30 minutes of jiggling wires it finally started. After that, sometimes it would start and quit after a couple miles but sometimes it would turnover but not fire at all.
It sat all winter then started right up (but with major exhaust smoke) then I shut it down and left it a couple days. It started again that following weekend, (2 weeks ago) not as much smoke. I pulled it out into the drive and gave it a little throttle (about 4000rpm) just to go to the end of the drive, but when I let out the clutch, I heard (and felt) a very loud backfire and it stalled. When I attempted a restart it turned over like no compression. So now I’m thinking something blew inside the engine. I wait 1 sec. I try it again and WOW Hey MC she started right up!
I want to get out to some club events but I’m still afraid to drive it. A local Porsche mechanic said he thinks it may be the 6 pin cd box, another said computer. What would be your guess without seeing it?
Is there anyone in SEM/PCA near Mt. Clemens area that could stop, look at and possibly fix this without charging an arm and a leg. These days can’t afford to lose an arm or leg let alone both. 🙂
I’m very disappointed with this car so far, maybe I should just get rid of it while I’m still BEHIND 🙂 So brings one more question to mind 3) What is this car worth (if it was running) in fair cond. and almost 100,000 miles
Thanks Barry
A — This must be the month for intermittents. Have faith, I am a stubborn German who enjoys a challenge. Over the last few years, a half dozen or so fearful folks have begun to venture far from their “AAA Plus” limit. To me the acid test is taking that long road test myself. To verify intermittents, I built a jumper box that allows me to monitor power to both ignition and fuel circuits and if one should drop out, supply power to the circuit that needs it. You might want to borrow it.
The CD box is not the first place I would look. Usually these fail totally, not occasionally. Far more common is a fuel pump relay failure or ignition cut relay. The turbos have an extra relay in the engine compartment that cuts ignition power slightly after you turn off the key. If you do not feel adventurous in the realm of electricity, I would give up early on this one however. What you can do, is follow the fuse box servicing process that I mentioned to Gary in the answer above. Even if that does not help, always start with the source of power and work your way in.
As far as smoke after sitting, don’t worry about it. The engine contains a large quantity of oil that will settle into the crankcase when it sits all winter and that first start up can be very disconcerting. Start to worry when it smokes every time!
Backfiring on this particular Porsche is a particularly troubling and perhaps costly problem. This model uses an archaic fuel injection design that is very sensitive to vacuum leaks in the intake system. Even if a vacuum leak did not cause the backfire, the event itself can CAUSE a new leak. During start up and warm up, the electronic fuel trim components are disabled. In this mode, the engine relies on mechanical fuel mixture control adjustment and vacuum leaks cause the mixture to go lean (not enough fuel) which can cause backfiring.
You might notice the large radiator-like device that dominates the engine compartment when you open the deck lid. This component, the intercooler, is removed during most services and the intercooler is sealed to the intake piping with large silicone rubber O-ring that get oil soaked, broken or squashed. These O-rings are a source of leaks that can cause backfiring and a loss of boost pressure during acceleration too.
As far as selling it, why give up so easy? Once you get it sorted out, you are going to have a ball. Compared to a boat, you are going to have a lot more fun with your Porsche since every weekend there is a driving or social event where you can sport around in your new toy. Besides, what did it cost last season when you filled up your boat? Now double it. Doesn’t that Porsche look better? –MC