My boy's car is recently hesitating at like 3500 rpm and backfires alot during normal street driving.he has stock pulsar motor(t-28) JW ecu cobra maf and front mount IC. we've checked the following regapped plugs to .028 ,new stock wires,cap& rotor,checked exhaust for leaks none.checked vacuum 15psi.checked for leaks don't hear any with stethoscope.checked all vitals with mdm100 all is to spec. what now. we are tempted to clean the 4 tb's next if all fails they look dirty. at least #4. also newo2 sensor. should we ground the cobra maf do we have to? any info greatly appreciated. I'm thinking leaky injector could clan and change o-rings. thanks in advance.

any one?

hook up a fuel pressure gauge and check to see if that's within spec. The fuel pressure regulator could have gone bad. When mine went bad, it was running rich as hell, hesitating a little, and backfiring. Good luck.

Khiem

fuel pressure was too high then we changed the regulator with another one and it got better but still 3-4 psi higher than the norm.43 or 46psi I forgot what it's supposed to be. but a little better still hesitates a bit at3000 or so rpm. any other ideas?

Originally posted by redman007
fuel pressure was too high then we changed the regulator with another one and it got better but still 3-4 psi higher than the norm.43 or 46psi I forgot what it's supposed to be. but a little better still hesitates a bit at3000 or so rpm. any other ideas? My friends car did the same thing (idled bad) until boost hit. Im talking seriuos sputtering, and ocasionally a loud backfire. Come to find out the TPS voltage was way off, and it was also not grounded right.

It could be a lot of things. My car is doing the same thing and so far haven't figured it out. I have a huge coolant leak so until i fix that i'm out.
I would check ALL of your connections. When swapping out the engine sometimes you break a lot of little things and never even notice. I would double check all of your connections and wiring-extended o2 sensor-dropping resistors etc.. and verify that first.
Could be the coil-fuel pressure reg- wrong program on the ecu.
Good luck.
Brent

thanks for the input fellas but checked allthat stuff and still kicking our asses. last resort would be to take it to vinny tan(performance factory $$).will fill you guys in when problem is found and fixed. for the mean time keep it coming guys.