s13 blacktop very slight missfire. any ideas?

[nismotuner1]

so my car started to miss fire a couple weeks ago. only above 3000rpm. I first noticed this on the highway cruzing in 5th gear the tach was bouncing between 3000 and 3200 rpms. but that is the only way you can tell while driving it is very slight. if the car is parked and you hold the rpms at 3000 you hear a slight pop out the exhaust when the tach bounces. it does not do this under wot. I have checked timing 15 btdc, plugs,ecu (no codes). alternator is putting out 14 volts I added 2 chassis grounds and an engine ground due to the last time on the highway the temp gauge was bouncing when the tach was. so I thought is might be a ground/ voltage issue. I did this swap last summer and this is the only problem I have had with it so far. any input would be appreciated.

[Sil80315]

Ah yes the infamous misfire the sr's do. Matt rosco had the same problem.. at crusing speed he would get that little pop but at wot it was gone..and it was right around the same rpm range

[nismotuner1]

so what is the solution my friend?

[nismotuner1]

so I checked the plugs again they were fouled out due to mmt a fuel additive. very rusty color. so I changed them brand new set of ngk pfr6b .028 gap. and I have the same problem. Any other ideas?

[nismotuner1]

nobody?

[Sil80315]

check TPS. might throw timing when the peddle is pushed a certain amount

[nismotuner1]

just checked tps voltage. It is .48 at closed and 4.26 at wot. from what I have read there is no way to check the cas right?

[the converted]

How is your o2 sensor? Maybe clean the MAF?

[nismotuner1]

I cleaned the maf when this started but it did not help at all. and I changed the 02 sensor a month ago with a brand new bosch 95 300zx tt one.

[nismotuner1]

any other ideas anyone?

[the converted]

I saw someone say something about ka's like to have a 3k issue if they are running an auto tps on a manual ecu. Just a shot in the dark, but any chance you have an auto tps?

[nismotuner1]

nope I have the 3 wire 5-speed tps and a e5 blacktop ecu. must be this is not a common problem.

[Sil80315]

well if you need to test the coil packs or the ignitor chip. let me know. I have an extra set