Hello guys, I want to ask if someone here has ever replaced their ECU with a new (rebuilt) unit and then your car would not start? It turns over but no spark (I smell fuel so a good bet it's getting fuel). When I put the old one back in car starts fine. Am trying to find a power loss issue, mid range, is how I got here but I will not bore you with that problem yet. Thanks for any help!

 

UPDATE: Gave up on the new ECU and sent it back and put the old one back in. Car still starts and idles good but the original problem of a power loss right at 2400 rpm still exists. If I hold the accelerator right at 2400 power drops off to 1500 rpm and then pulsates back and forth between the two rpms. I can power through that range and drive the car but at higher speed there is a significant power loss. No vac leaks, catalytic convertor was cut off with no change, fuel press reg and temp probe check out, spark to every plug, throttle position switch checks, air flow meter checks, and the air regulator valve (new) checks. The latest codes are still giving me 31 for AC system and 41 for Fuel temp sensor circuit which both again check good. Anyone out there ever run into this kind of a problem with their Z31?
85 Std trans, non turbo

 

It sounds like your in Limp mode, check your mass airflow meter if it's plugged in correctly.