so my high compression gsr 11.6:1misfires under more than ten percent throttle above like 3000rpm,

This started happening radomly so i assumed weak ignition so ive replace the coil, cap and rotor. What else should i check

Tuned on s300 runs the same on old maps plz help

 

No CEL? Maybe check if the plugs are fouled.

 

yea check the plugs!! also maybe the map sensor is bad. Hows the timing? did you check the mech timing just in case you might be off on the cam gears from a slipped belt?

 

Thanks for the reply ive tried different plugs, anyone know how to test a map sensor? Shoot out some more ideas on sensors that would cause this. And my s300 shows me no error codes. Also re syNced the timing and that didnt change anything

 

Hows your injectors?

 

380cc s2000 injectors, wideband says afr is good.

Update: changed plugs ngk iridium, car runs hard for 20 minutes and then the misfire returns, switched out to another distributor and now the tach doesnt work with the same misfires, also idle surges a bit

 

you might have the wrong distributor, i believe obd1 distributors uses the tach signal from the ecu. sounds like it could be a bad distributor from the start but the new plugs fixed the issue for 20 mins sounds like it could be plug related or your loosing spark.

Check for small vacuum leaks for idle surge and clean out the IACV won't hurt to try.