cid042

I have big troubles with my cup : It doesn't run on all its cylinders and we don't find where it comes from.

Here is the complete story :

On April, the 30th :
Working on the car at the workshop, we changed the gearbox potentiometer and adjust it, trying to solve an engaged gear display problem in the motec (flips between 2 and 3 and sometimes shows 0) and a problem with the ignition cut sometimes not happening on upshift (at the same time as the display issue).

Tests on the lift, engine on, changing gears with some rpm, everything runs fine. Te engine runs like a charm.


In the afternoon, I trailer the car (rearward on an open trailer) under load of rain. I have to let it sleep outside, under the rain.


On May, the 1st : Lurcy Levis - Test day for the gear display/ign cut issue :
The car is difficult to start, spit out some water and seem to run on 4 cylinders (the first 912 ou 356 cup ever !), stalling immediatly when you let the throttle at rest.

10:00 AM : Loading the car on the trailer.


Back to the shop : The car is now completely dry (15 days in the workshop). Trying to start : It is worse ! It seems to run on 2 cylinders ! (2 cv cup !).

We have changed all the coils, all the spark plugs, the two lambas and it is now back to its "4 cylinders" state. Bought the Modas, didn't see any error, and doesn't seem to be very useful to diagnose my problem (but this our first time Modas experience).

We have connected the Durametric, cleared all the error codes, nothing better. The following error codes keeps coming back :
* 78 - Unknown fault
* 5A - Unknown fault
* Several 80 - Unknown fault

I have a race in 10 days and we are out of ideas . If someone knows what these error codes mean or has an idea...

mobonic

check the cam sensor

cid042

Will check. Thanks

Other ideas (just in case...) ?

drbooba1

Make absolutely sure the ground strap near cyl. 6 is attached to the chassis and the engine

tedean

Assuming you have verified spark to plugs (plug out,grounded, engine cranked,see spark) Check the valve springs, trust me. It might sound totally unrelated, but you should do it.

https://rennlist.com/forums/porsche-...e-mystery.html

Polesitter

Have you tried a different ECU ?

cid042

Not yet, and we do not have another 2008 ECU to try. Only a 2007 or a 996 GT3R and don't know how to save the map and load another one in either of them.

We are having a blow-by test done today and a double check of the engine ground strap.

If blow-by is ok, next is the cam sensor and we will try to find another 2008 ECU.

Next will be engine down...

Many thanks to all for your ideas !

claykos

if you are also having problems with the dash it sounds like an electrical issue to me.... perhaps some damage in the harness. I think the 2007 ECU should also be adequate for testing

cid042

The dash seems ok.

The blow-by is good. Ground strap also.

Going to try the 2007 ECU asap. I also think (hope ?) that if this is the problem, the engine should at least run on all its cylinders, even with a 2007 ECU.

Polesitter

Agree with Claykos. It sounds electrical to me too and I would suggest checking the harness. One problem is that a visual inspection of the harness might not find the problem. We went through a crazy diagnostic chase for a power problem in a 2011 cup and after endless attempts (including pulling the motor and sending it to PMNA) could not find the problem.

At the end of the day (which was weeks) it was a tiny nick in the harness which emanated from an unrelated soldering repair that was causing the problem. It was virtually undetectable and we had to actually change the harness in order to determine the problem.

cid042

Well, we have checked with the ECU of a 2007 and tested my 2008 ECU on the 2007 cup, and guess what : The problem follows the ECU.

The good point is that the cause has been identified. The bad one is that I don't know if an ECU is repairable ?

Do I have to buy one new ? Don't know the price, but it, for sure, will hurt... And there is no chance to get one for next week end...

Finding one used would be luck, but do I have to get a 2008 one or would a 2009 also work ? Is the map specially made for the car (which I doubt of...) ?

If anyone has one to sell... (Guess US & Euro cars ECU are the same)

Many thanks to all for your very useful advices.

Polesitter

I'm glad you found the problem. I don't know much about ECU repairs, but assume it could be either a hardware or software issue. If the latter, they may be able to re-flash it but this would probably need to be done by Porsche Motorsports. You also may be able to hunt up a used one. Motorsports might exchange one on loan while they look at your original so you can race next week. Good Luck !

cid042

Thanks Polesitter.

I have found a company in UK that can repair them and seems to know the kind of problem I am facing : It should be an "ignition driver" in the ECU...

ECU will ship Monday. I will let you know.

We are talking about less than 300 Eur for the shipping 2 ways, testing and repair Vs more than 5000 Eur for a new one...

Glen

Let us know how it goes and who.
Would be a great resource.
Good luck!

cid042

Be sure, I'll do ! ;-)