teg_95

also posted this in forced induction. Wasnt to sure on where the best place was so ill post here also...

i have a 94 boosted gsr. the car will run great for about 30-45 minutes of drive time then it just starts missing on cylinder 4, got spark but no fuel. so i got my volt meter out and check the power going to the injector harness, i have a constant 12.5 volts coming out of both sides of the pigtail. if im correct one should be a "signal/ground" for pulse or what not? so i checked the other pigtails and they are all reading 12.5 and .0009 or some some number in that nature. i figured if it was a short in the harness it wouldnt have any power to the pigtail, correct? so i put the factory ecu back in and volts show to be fine on both side of the pigtail, then i put the neptune ecu back in and it runs fine again for another 30-45 minutes or so. someone please shed some light on this please. anything will be greatly appreciated...

its bone stock on 10lbs with a precision 5731 billet wheel, rc 750cc's and a walbro 255.

holmesnmanny

The yellow/black(normally this is the color......could be different color for your car) will be constant power. The other side will be grounded by the ecu when it wants to open the injector. Each injector ground-side will go back to the ecu. You can check for continuity at each ecu connector pin. However, what you can also do is get a efi quick probe and this will easily test each injector for smooth non-intermittent firing. What are you saying is happening as the difference in either ecu ?

teg_95

its seems as if i put the factory p72 in and then switch it right back out to the chipped p28 the problem goes away. last time i parked the car (friday night) it was running fine, when and tried to drive it yesterday and as soon as i started it, it was missing on 4 again. didnt have time to swap ecus this time to see if the problem goes away. but the past 4 time its done it i swapped ecu's back and forth and problem was gone. i found some splicing in the wiring harness right at the ecu in the floor board. not exactly sure what was going on with it but from what i gathered on some ecu pinouts looks like someone tried to jump the knock sensor to the IAB or something like that. dont know anything about wiring so bear with me please.. and are you talking about like a noid light?

hybridmiklo

thats normal. You will see power on both sides of the plug on injectors when probing. What you need is a noid light. The injector pulse is too fast to be measured my a dmm.