3.6 Running rich/backfiring - Where do I start checking

[katigbr]

PPBB'ers,
My ongoing saga with Gretchen's 3.6 swap continues. I've been trying to sort out a severe hestitation problem with anything more than part throttle. She idles and will pull away with a slow and steady throttle. Anything more agressive and she'll bog and stumble. I've been able to eliminate fuel starvation and ignition problems. I've just installed my new Flowmaster dual in/dual out setup, replacing my Supertrapps. I can now detect heavy black soot deposits on the pipes. There is so much soot that every time I start I leave a dark sooty ring on my driveway.

My thinking, based on my limited experience and what I've been able to read, is that the possible culprits are:

1) A/F sensor
2) Full throttle sensor
3) O2 sensor (I'm sure this thing is inoperative with the over-rich conditions
4) The DME is a custom chip setup from Cyntex. Could there be a mapping problem?

I don't have any engine diagnostic manuals for the 964 engine. Does anyone have any diagnostic checklists or sensor specs they are willing to share. I've got a digital multimeter and I'm not afraid to use it.

Any other suggestions would be most appreciated. I've got a DE in 5 days and would like to really stretch her legs.

Thanks,
Rick

[Bill Verburg]

Wish I could help( ), the only thing I can contribute is that I doubt its the O₂ sensor, it should go into a rich but drivable failsafe mode if it were. There is an easy test of the O₂ sensor though, hook up a high impedence volt meter, start engine and let idle, after a short while (less than 2 min) O₂ sensor voltage should begin fluctuating between ~.1 and ~.9 VDC, then just remove the oil filter cap to this will admit unmetered air to the intake simulating a lean condition, O₂ voltage should drop. Are you sure that the cylider head temperature sensor is hooked up and functioning.

[hbrand]

are you sure you do not have an itake valve problem??

[stormcrow]

Sounds like your running extermly rich. Black soot is lack of oxygen. Try leaning it out a little.

Steve

[FRED/LI]

I'll assume that you moved the engine along with the brain and ingnition/induction systems from the 3.6 as found in a C2 or like.
If so, the system is highly sensitive to voltage in order for the brain to register actual operating conditions. I won't try to recap an incident related recently, but suffice to say, that if the O2 sensor and knock sensor are deprived of full voltage, they can fool the brain into all sorts of misdiagnosis. Good luck, this may not be the problem, but often, it helps to go back to the basics and work up.

[katigbr]

PPBB'ers,
Thanks for all your help and advice. I went back through all the oil breather, vacuum and connectors again one more time. I discovered the MAFS connection wasn't seated correctly (the one that you can't see). Clicked it into place and started her up. YAAAAAHOOOOOOO!!!! WOW!!!! I'll post the .wav file later. Unfortunately, Montreal just got hit with a 4 inch dumping of snow last night.....I'll have to wait until the roads dry before I can road test her.

Thanks again.

Rick

[AES]

Snow??????