My 87 twinscrew now - while at Sharks and upon returning - frequently wants to die on startup. I's running VERY rich at that point. If I can get it through that stage, it stops running rich and runs fine. It doesn't always do this. Sometimes it starts and runs just fine. The rich make be think it might be the ISV (Idle stabilization valve)?

I've also noticed that after this, the O2 sensor indicated very lean for a brief time. I have also wondered if the O2 sensor might be the culprit.

Haven't started on it yet, just looking for similar experiences?

Anyone, anyone, Ferris?

Thanks
Rod

Blue one is still at body shop, it looks so pathetic without a bumper cover and fender. ;-(

 

Sound like Temp 2 sensor, also check the condition of the wires to the temp 2 sensor.

 

Rod,

I experienced something similar. My car would get super rich at startup and then lean while running. Here's what I did - it's not perfect, but the car runs great now. I still need to find out why it's doing this, but this should helpfor a while.

For the richness, I set all of the warmup enrichment values above 50*F to 0. This helped the richness.

For the running lean, highlight and copt all the values in your Cruise - cat fuel map and past them into the Base- Non-cat fuel map. The go to the fuel parameters page and under the Oxygen Sensor area, tell is to force non-cat mode. This disables the O2 sensor.

You should see the car running much better after ths. I'm still trying to figure out why the O2 wants to lean everything out. Plan to do some data logging this afternoon or this weekend and figure it out.

Hope this helps.

 

The Temp II could affect running but in this case I doubt it because he's running lean once warmed up.

If the Temp II is reading low temps, it will be normal on cold startup and rich while running hot.

If it reading high, then cold startups will be lean and hot operation will be normal.

Rod symptoms are rich on startup and lean while running hot. I don't see how the Temp II could affect that.

 

There is no relation between the ISV and the air-fuel mixture, IIRC.

 

I would make sure the harness grounds are clean and tight, especially the two for the FI harness that are at the rear of the block on the ends of the throttle wheel bracket. How does it behave if you unplug the MAF during one of these events? (Stop the motor, unlplug, restart, observe, stop the motor, plug back in, restart, observe)

 

Again, if he switched to non-cat mode, and the car runs fine, then it's not MAF. If it still runs crappy, then it points to a MAF, false air, or a bad tune.