Alright so Ive been dealing with a problem from my 96 d1 for the past two weeks. Its been running rough and idling rough... but its not an all the time thing. Sometimes it will run great for most of the day and run like total ***.

Its losing power and sputtering and rough idling, like a misfire

now for the fun stuff..., I used my ultra guage for all my readings and this is were things get interesting...

when this problems occurs short term trims on both banks read a constant 0.00 and all four of my 02s will read less and .1V(something like 0.045V)

now it does not do this ALL the time. sometimes right from a cold start or just cruising and sometimes it wont do it at all for a day its random.

fuel pressure is questionable... when pump primes I get about 39-40ish psi, and when running(when its not bogging down) is about 30psi(seems not quite right to me)... I have not be able to check it under load but when revving in park my pressure will drop to about 27-28 psi.

so far I have cleaned the MAF, swapped the MAF with good known one, swapped TPS, IACV, checked for Vac leaks, I have recently changed the plugs and fuel filter, checked spark, all injectors ohmed out fine.

Im really at a loss here, and have no idea whats going on... worst of all, NO CODES.....

 

Fuel pressure 34 - 37 psi while running. How old is the pump and have you checked it's condition physically?

One other thing, the UG will display odd readings when it's running like **** - hence it's running like ****. The fuel pump will not toss a code nor will a short or bad connection. I wouldn't toss too many parts at it, gets expensive and leads you down the wrong rabbit hole.

I went through an engine cutting off without notice for two months, thought for sure it was a crank sensor because it mirrored that symptom. It wasn't the crank sensor, it was a wet connection that corroded and overheated loosing electrical contact for the fuel pump that was four months old..... So that's what you may be facing, dig in.

 

when its running bad what is the weather?
check your grounds too

 

turns out it was the ECU.