3.8L idle/stalling issues

[Moriartyhlms]

Hello,
Have some post-rebuild bugs I'm hoping some of you experts can help me with. My engine has a loping idle and stalls if I'm not careful (sudden throttle lift off, putting in the clutch; like it can't catch itself in time).

My car is a 1990 964 C2. Engine is a 3.8L with cams, varioram, 993 injection, 993 RoW OBD1 DME, 993 OBD2 DME harness converted to OBD1 (might that be part of the problem?), B&B exhaust, Steve Wong chip, and lightweight flywheel.

My best guess is that it's an issue with DME/harness/chip, or fuel pressure regulator, or distributor hall effect, maybe a vacuum leak...I'm really at a loss. Have already replaced the following with new parts: MAF sensor, ICV, knock sensors, flywheel position sensor, engine head temp. sensor.

Engine runs ok with MAF unplugged, but is rich and backfires, pops, etc.. And, for what it's worth, engine seems to idle a little better with clutch in.
Thanks,
Sam

[Moriartyhlms]

Further, does this DME look appropriate?
Bosch pn 0.261.203.674


And here's the engine (everybody likes pictures):

[preston_brown]

That engine ECU / DME was never intended to run a modified motor. What changes or maaping did you do to it to run your newly built motor? If none, no surprises you are having issues...

The harness shouldn't be the issue unless a connection (or multiple) are missing.

[Moriartyhlms]

I'm running a custom Steve Wong chip set up for my modifications, should hopefully get in the ballpark as far as mapping. I agree that attempting to run a stock map with a modified engine will certainly have problems.

I tried to do the full adaptation again today - 3 minute of ignition power only, then 10 minutes of idling. Seemed to make a difference, engine didn't dip revs quite as deep. Still a little stally and still backfires/pops a little as well as idling slightly lopey. Call it progress. Perhaps just putting some miles on will improve the adaptation?

Thanks for the reply.

[knorrena]

I have two thoughts. The first is the harness. I just finished a varioram conversion on my 95. When I got the intake it came with a 96 ecu and the 96 harness. They are quite different and it would take more work than I can imagine to convert a harness. Maybe, you have a bad crimp connection or a bad solder somewhere?

My other thought is that you might be having troubles with your isv. It might need cleaning or perhaps its a victim of your harness.

[Moriartyhlms]

Yeah, I'm not 100% confident in my harness (and I certainly wouldn't recommend anyone else try converting a harness). But, I've also been through all the wiring diagrams and have checked all pins for connectivity multiple times. I think my next task may be adapting the OBD diagnostics port so I can read 993 faults and stop guessing what's wrong.

Knorrena: interested to hear how your varioram conversion went.

Thanks