My car is acting very, very bad when it gets into closed loop. RPMs are hesitating really bad (at iddle and when running, until about 3k), sometimes I can hear 'popping' from exhaust (backfiring?) and under acceleration I can feel car 'choking'. I've run pretty long datamster scan and I just don't know what is going on. My RPMs are crazy, PCM reads like 1200 - 1200 - 4800 - 1200 - 1200 or so, there are lots (!) of sudden jumps, tachometer jumps only a little bit (because those PCM jumps lasts just for a part of a second) so does the oil pressure. I do not know yet what all those trims / terms / mV means, but I'm learning it (Injurner's article) and know they are also wicked.
I've changed recently plugs, fuel filter, air filter, I may have intake oil leak. What device tells the PCM those RPM readings? What may be wrong?

Here are the files: uni [0.8 MB], zip [0.2 MB].

I would be glad for a quick look at them (I can export to CSV, but don't know which data are most important, which one to pick).

Thanks for any input.

 

do you have a check engine light?
is this on your 94?
It could be the low res opti signal. you should have a DTC 16 though if that was it.

I cant get your file to work.

 

Yes, it's on my '94. The problem started like 3 months ago, but it seems to more 'evident' form day to day. No DTC codes, I've cleared PCM battery fuse, no codes appeared either.
I've already read, that OPTI tells RPM, so maybe it's time to replace it (75k on odometer), but why so big difference it those readings for such a small time increment? And what reads RPMs in open loop, OPTI either?