[zcar80nj]

I have a 1980 ZX that has a bimodal behavior. It will be running fine and then suddenly switch to Darth-ZX. In Darth mode, any RPM below 2800 causes sputtering, coughing, bucking, etc. It may stall but starts up immediately. If I can get the RPM up to 2800, Darth mode instantly goes away and the car performs normally. If I vary the RPM 2800 +/- 200 it feels like a switch is turning on and off as the car instantly changes behavior as it crosses the 2800RPM line. A few minutes later, the behavior goes away and operations below 2800RPM are normal.

The car can flip flop between Darth and normal modes several times during a 30 minute drive. Darth mode does not happen when the car is cold (e.g., first 10 minutes of driving). I usually assume that intermittent behavior is connection related but the 2800RPM behavior leaves me puzzled.

I have done the connector scrubbing task on the ignition module & all the sensor wires on the water housing. I replaced the ignition module about 5 years ago when I had the Tac-goes-to-zero problem. I replaced the fuel pressure regulator this summer.

Any ideas would be greatly appreciated. - steve

 

[ferrari_f]

Hi,
I had the exact same problem with my 79 280ZX. I went through the entire ingition, thinking that it wasn't firing correctly. It turned out to be the fuel pump. So, if you haven't already, i would try replacing your fuel pump.
Zach

 

[Dave280ZX]

I would guess that the throttle posistion switch went out of adjustment. If the idle contacts close too soon, the ECU adjusts for idle at 2800 RPM. The only other thing I can think of would be the air flow meter is giving a false reading below 2800.

Dave