RotaryEvolution

iTrader: (30)

this is for an S5 TII 89 FC that has the powerFC with banzai adapter harness.

the story: the engine was built and tuned about 3 years ago, made 449WHP and eventually popped after about 30k miles. i rebuilt the engine with goopy 3mm seals and replaced the t70 non BB turbo with a Garrett GT3571R turbo with Tial sport 46mm wastegate.

the car ran fine until it popped, on initial startup it had a difficult time starting, with a spare crank angle sensor plugged in i could hear the injectors firing irregularly, unless i spun the crank sensor fast enough to get a good signal it would only fire once in a while on whichever injector it felt like hitting.

this issue is more prominent when the car is cold and it really does not want to start after sitting and fully cooled off. i can eventually get it to catch and start, when fully warmed up it will intermittently go into a seemingly fuel cut mode off idle where it will bounce from 2000RPMs back down to below 1000 and is undrivable. it doesn't happen all of the time but it is an issue that obviously needs to be resolved.

all inputs from the ECU are within parameters, the TPS is only slightly reading on the high end at 1.5v with the idle turned up on the fresh engine and full bridgeport idling at 1500 RPMs. the RPM signal is cut when the fuel cut issue is apparent, basically as if the throttle is closed and the engine is cutting fuel/ignition for deceleration.

i'm going to try closing the air gap for the crank angle sensor triggers to make sure it isn't losing the signal, also thinking it may be losing voltage to the EGI circuit feeding power to the coils/injectors. last thought i have is that the crank sensor wires have melted in the harness causing high resistance in the crank trigger circuit.

i had the rev cut set to 4200 RPMs for the break in miles, even with the rev cut set higher it makes no difference to this issue. it rev cuts normally at the set parameters but the issue also seems to be more common with the commander plugged in but still happens with it unplugged so i have ruled out the commander shorting out as a cause. the injectors all have been serviced and rebuilt by RC engineering, it has a supra TT pump with KB boost-a-pump and a-1000 regulator idling fuel pressure is 40 psi and fairly constant(not exact since it is a FBP engine) so i have ruled out the primary fuel system as an issue but i will ohm test the primary injectors soon..

just looking for ideas if anyone has run into a similar issue before, i don't want to spend too much time dissecting the harness if i don't have to. the main engine harness is only about 8 years old as it was replaced with new 2 rebuilds ago by another shop, it has definitely been warmed up thoroughly in the area above the turbine housing however.

i have already swapped the ECU with another PowerFC and there is no change.

Banzai-Racing

iTrader: (11)

This may help you with your troubleshooting. With our adapter the tach gets the signal directly from the PFC, the trailing coil no longer plays a role in feeding the signal. The PFC gets the RPM signal from the CAS, if the PFC is not dropping power completely then there is either an issue with the CAS, the harness or potentially one of the main grounds.

RotaryEvolution

iTrader: (30)

it seems like a harness issue, only problem is the RPM signal seems to be fine throughout the RPM range even when the injectors are firing intermittently. it's just irritating that the injectors pulse irregularly when cranking, the irregular running condition only happens some of the time, usually when the engine is nice and hot. once started the car runs fine for a while then has the issue pop up after an hour or so of run time, making it difficult to diagnose.

i'm going to double check the TPS to make sure it's still within the parameters when the issue is apparent. i did just add additional grounds from the battery to the 2 ground terminals on the engine harness to see if that was a potential problem. guess i'll also double check the voltage to the injectors with the ignition on and while cranking to be sure that isn't an issue. could simply be the main relay crapping out.

i just need to get it sorted out so it will be ready to tune the car, it's not safe to really boost it in the current state it's in.

RotaryEvolution

iTrader: (30)

wound up being a bad connection at the + terminal in the leading coil pack connector. i cut out the connector and used some larger gold spade terminals which seems to have cured the problem.