Wondering if anyone had had this issue before. 1990 SC, runs great when cold (open loop), once it gets to.operating temp and you drive about 2 minutes, at WOT it falls flat and backfires at 3000 RPM. It will run fine at WOT when at temp for the first 2 minutes after a startup. So pull over key off, wait 2 minutes, it's ok again then 2 minutes later, same issue. I can get to 4500-5000 RPM driving normally, just no WOT. No CEL on dash, however, when running KOEO / KOER, I have codes coming up. 25 - Knock Not Sensed During Dynamic Response Test (R), 66 - , MAF signal below minimum test voltage of .4vdc (O,M,R), Transmission Fluid Temperature Circuit Grounded (M,O, 72 - Insufficient Manifold Absolute Pressure/Mass Air Flow Change During Dynamic Response Test (R)
73 - Insufficient Throttle Position Change During Dynamic Response Test (O,R)
74 - Brake On/Off Circuit Open–Not During Self Test (M,R) and 87 - Primary Fuel Pump Circuit Failure (M,O)
I want to say MAF, but issues didn't occur until I changed out the fuel filter. However, MAF could be bad if now it's overwhelming with fuel woth the new filter at WOT. Would this make sense as a diagnosis to my issue? Or does anyone else have any other probable cause? All sensors and coils, DIS, plugs etc are all new. Just MAF is old.
73 - Insufficient Throttle Position Change During Dynamic Response Test (O,R)
74 - Brake On/Off Circuit Open–Not During Self Test (M,R) and 87 - Primary Fuel Pump Circuit Failure (M,O)
I want to say MAF, but issues didn't occur until I changed out the fuel filter. However, MAF could be bad if now it's overwhelming with fuel woth the new filter at WOT. Would this make sense as a diagnosis to my issue? Or does anyone else have any other probable cause? All sensors and coils, DIS, plugs etc are all new. Just MAF is old.