Running rich... need help/advice please

[dkcaims]

Posted on 964 board, but no responses so far.
I'd like to have this resolved before the Porsche Parade, so I need your help.

A little background first...

The car is a supercharged 90 c4.
Recently has a new FTC1 (controls 7th injector & retards timing), a PSC1 (signal modifier to accommodate larger injectors, 30lb).
Also installed was a dashdaq monitoring AFR, Fuel Pressure and Boost.

Once everything was wired up and fined tuned the fuel maps, it ran fantastic for the last month, including immediate start-up and idle. WHAT A DIFFERENCE !!!
Note: o2 has been disconnected since tuning and ran great for the last month.
AFR's were consistently 14.2-14.7 at idle and under light load.
AFR's were 11.5-12.0 under full boost.

Just a couple days ago when starting, AFR's were just where the always are at start-up, 14.5-14.7
... but after 15 seconds or so at idle, the AFR's drop to a low of 10.3 and don't go over 11.0 even during a short drive around the block.

What I've checked so far...
Fuel Pressure good
Regulator diaphragm is good, no fuel leaking out of vacuum port.
Distributor belt good
Cleaned ISV
Pulled new injectors and had them checked. Thought maybe one or more was stuck open. All checked out fine, re-installed. Also checked 7th injector in case it was firing at idle, but it's not.
Re-connected O2 sensor, but same result.
Checked the coils today, appear to be in spec.

Possibilities...
Intake air leak somewhere ?
Faulty CHT sensor ? NOPE, installed new one a couple weeks ago.
Ground issues ? Cleaned up all ground points, so unless its a shorted ground somewhere in the harness, I don't think it's a ground issue.

Thanks in advance for any advice you can give.
Derek

Car looks so sad sitting in the garage... wants to be driven !

[dkcaims]

No one at all?
My regular tech is on extended vacation, so I went to another highly recommended tech nearby and he says 25-30 hrs to diagnose. I don't want to spend another 3 grand on diagnosing a problem.

Will have an oscilloscope by Sunday.

Nobody has any ideas?

[rsscotty]

It sounds like you have checked the likely suspects. Have you verified that the A/F ratio system is properly working and it is indeed rich. What brand of system are you using and what type of sensor. If it is that rich your spark plugs should be black.
Is there a chance the PSC1 is not working properly? Are you using the PC based software for the PSC1?

For all the problems you have had with this system you might consider Motec M84. We have had great success with it and we are running closed loop with a Bosch LSU 4.9 sensor. We also make a adapter that goes between the factory wiring harness and the M84 so you use your factory wiring and do just a few modifications in the engine bay wiring when you delete the air flow meter and change the throttle position switch. Just an option to consider.

I will keep thinking about your car and let you know if anything else comes to mind.