964 turbo 3.3 hesitation problem and difficulties to start when warm

[gagmi]

I own a 964 turbo 3,3 1992 with 55k miles on it. I have two problems:

1) the car start very well when cold, start very well when hot, but if when hot you stop for 45 minutes (approx.) then the car will not start... can help me?

2) when I ride the car and push the throttle to accelerate, at 3,500 rpm most of the times there's hesitation + black smoke.

I have change the Oxygen sensor, the reference sensor, the fuel pumps, what else can I do before changing DME control unit (+/- 3500$)?

[spuggy]

Originally Posted by gagmi

2) when I ride the car and push the throttle to accelerate, at 3,500 rpm most of the times there's hesitation + black smoke.

Pig rich and bogging down when the boost enrichment circuit kicks in - sounds familiar...

Originally Posted by gagmi

I have change the Oxygen sensor, the reference sensor, the fuel pumps, what else can I do before changing DME control unit (+/- 3500$)?

'92 965? I believe that you have a 3.3 turbo motor with the late extra Lamba junk and possibly more emissions thingies bolted onto it.

Which means you don't have DME, you have a CIS system with what is misleadingly called a Warm Up Regulator or WUR. (It would be better if it were called a Control Pressure Regulator, because that is what it does...)

You should be able to eliminate the Lambda stuff from the equation by simply unplugging it to check. I doubt it's the issue, it sounds like you need to get the control pressures checked, especially for boost enrichment.

Brian Leaske rebuilds 930 WURs and modifies them to be adjustable for cold control pressure, warm control pressure and boost enrichment. Might be the way to go if you can't get yours back to spec.

I'd say the first thing to do is to measure your control pressures and see what's going on. It would likely be more convenient to be on a dyno to check the boost enrichment

[gagmi]

wher can i disconnect the Lambda?

[JFairman]

Follow the wire harness from the oxygen sensor till it comes to a junction plug. Then unplug it.

Do not unplug the pulse valve or you'll lean out your motor.
The fuel head differential valves are adjusted to give correct flow and air fuel ratio with the pulse valve operating.

[911st]

If you are still running a Cat I do not know if I would disable the Lambda function.

I doubt that is your problem. Have you checked your control pressure, CO, and for vac leaks?

Might check the small tube from the intake manifold to the WUR and if there is another small tube that dumps off the WUR to atmosphere, check that it is not restricted.

I think that used to be a symptom of the older fuel heads. I think they used to build up pressure above the metering plunger and go full rich but the C2 has a mod the is supposed to keep that from happening. I think the test was to push the metering plate down manually to release the pressure and then see if the car would then start. I could be way off on this.

Also, once it starts dose is smoke like it is the end of the world?

Do not replace any of the electronics. If it runs you are good. If you replace anything replace the WUR as they do go out of spec over time. Mine did on my 91.

I have to say I am reaching a bit here.

Good luck.

[911st]

Check the Intercooler to manfold seal. If you get black smoke at 3500 that is when you go on full boost. If you have a leak there the motor blow air out there and you will go very rich.