thank you for your advice tekkie, michael and tassuperkart. I had some progress today when I switched the cylinder 2 and 4 injector leads over and when I pulled the coil pack plug on cylinder 4 there was a drop in idle upon pulling cylinder 2s coil pack, there was no drop in idle RPM so I've definitely isolated it down to the #4 injector wires (which are all new) so it must be CAS or ECU side (arghhh can't wait to get my multimeter back) My S1 CAS looks pretty beaten up, so it may be a good time to replace also. Wiring specialties sent me a loom with both a S2 (later style CAS plug) and a S1 plug. Would an later style CAS bolt up to an early style vg30? :br:
Im doubting its a CAS M8 unless the4 timing slot for triggering #4 is clagged with gunk. this is only ever an issue with the synch timer slots around the outside. What Im wondering is, sometimes injector drivers in the ECU take a dim view of being shorted to ground or possibly even pulled to +12v without the inductive load of an injector. It depends on the circuit type and a far smarter man than myself is needed to know for sure.! However, Im wondering if theres a possibility that whatever fault might have been present in the old loom had damaged the #4 injector driver in both ECU's. A "noid" light might show something but without just swapping out another ECU, the only way youll know is to look at the injector driver output waveform with an ocilliscope. E
She's on all 6!! Tried another jspec ECU and she roared to life. Couldn't be happier. Thanks guys for all your help. I'm gonna say combination of bad ECU and bad old wiring loom. I'm gonna keep my friends jspec NA auto ECU. I know the differences between Jspec and Auspec ECUs are mainly the fuel maps. I've been using 95 ULP with my auspec ECU, should I be bumping up to 98 with a jspec setup?
2 Faulty ECU's. Who would have guesed. Happy that you found the fault. Annoying when another unit is tried. This goes to show that diagnostics are the best method to fault find even though repair by replacement is simpler. The voltmeter check would have shown a lower voltage on the positive injector lead all the way back to the ECU connector. A few members guessed correctly. Enjoy the car. MichaelZ
nah it wouldn't.. the positive feed for the injector doesnt go to the ECU, it goes to the harness plug infront of the relay box in the engine bay.. the ECU only grounds signal.. all 6 injectors are connected together (5 at the back of the plenum and one of them way further down the line for some reason) and then connected to permanent (not ignition) power with 6 individual grounds going to the ECU noid light would have helped
Correction. the neagtive lead would show incorrect voltage I stand corrected. The negative injector voltage would have shown a voltage drop across the negative lead due to the faulty ECU transistor driver having a higher "on" resistance to ground than all the other injector driver transistors. Michael Z
Wellll...nah.... and...yeah. Using a multimeter, if you probe at the ecu plugs, youll find +12v on all the injector wires VIA a low impedance injector! Semantics!!!!! E
