wierd electrical issue

[z32skyline]

I have this issue I can seem to figure out. Z32 with Rb26/ z32 maf sensors/stock turbos/750cc inj/jim wolf ecu. Everything else factory. A few months ago this issue came about, basically when I turn ignition to ON the fuel pump would prime continuously, I swapped out the relay by the kick panel and that solved that issue. But even after I did that car would not start, it would flood, sometimes I could even hear injectors clicking with the key on the ON position while I stood by engine. Took me a while to figure out that If I disconnected the maf sensors car would fire right up. But as soon as I connect them back car dies I instantly. When cold, car will sometimes start with both connected, but as It warms up it will eventually die. It will idle fine for as long as I leave it on if both maf sensors are disconnected sometimes with one too. The other thing I found out is that it will not start if the aac valve is disconnected, If I start it and disconnect it car will die instantly. When it is plugged back in with the key on the ON position the fuel pump primes, im not really sure why. Also, when I is unplugged and key in turned to ON it will prime for like 1 or 2 secs, instead of the 5 or so. I did find that I had some stripped wires to where wire come out into firewall (probably the damn mice, I found a bunch of mouse **** in different parts of engine bay, I live way out in the woods)
Anyhow, I have replaced wires to both mafs with new wiring and just about all the wires that go from ecu to sensors/relay box. I have tried 3 different ECUs with same exact results. All 3 ECUs give me code 12. I have also tried brand new MAF sensors with same results. Starting to get pretty frustrated.
Any suggestions on what to try next or has anyone had a similar issue? Any help would be greatly appreciated.
Thanks in advance!

[bobbo]

Do you have the RB service manual?

[Skym]

Sometimes the plug on ECU side doesn't sit properly into the ECU and can bend.

From memory, code 12 should be MAF's. Have you checked the earths??? Error codes are turned off by earthing the plug, hence why I'm thinking there is a earthing problem if the code keeps popping up on ECU. Bad earths would affect the fuel pump, ignition (usually blows the ignition fuse if there's no earth) as well.

Injectors clicking is activated by the turning shaft on CAS > ECU > injectors.

[z32skyline]

Ive replaced grounds to mafs and all other sensors as well with no luck. code 12 is mafs, and I have tried 2 brand new ones and still had same result. Before this happened I ran the car with aac disconnected because it seemed to run and idle way better with it unplugged. Now i cant disconnect it because car will instantly die, and will not start until it is connected again. I also tried disconnecting the aac and hot wiring the fuel pump to see if car will start and had no luck with that either. It seems as if the aac sends the signal to start car. Before I figured out that car would start with mafs unplugged, and everything was plugged including aac it seemed like it was getting excessive fuel causing it to flood and not start. I know that by turning the cas with hand the injectors and coils will go click and spark and that is still working as should. I have also replaced all wiring from ecu to cas, aac, iac, injectors, coils, o2 sensors, just about every wire that comes out of ecu and in to engine bay.

[hp44incgtr]

Buy yo self an good multimeter make it yo new friend get the wire diagram and do proper testing that's the only way.

[Skym]

I agree, most likely a wiring problem (MAF error code).

Usually the stock plugs are not good at holding onto the wires thus cause these types of problems (wiggling the wiring sometimes shows it up, especially with TPS that can make the engine stumble, then stall if wiggle the wiring enough). Some wrap the wires on plug side with I think tape to give extra grip.

Flooding is probably tune related, as ECU wouldn't be set for 750cc injectors and with fuel pump hardwired it would be supplying more fuel at idle than needed (MAF input affects the injectors, hence why I'm thinking that). The stock FPR has small orifice which causes higher fuel pressure thus engine floods. Nismo FPR or Tomei FPR or similar local made FPR can help, but I wouldn't back off the fuel pressure with bigger injectors (might run lean), I would do it via ECU tune. Sometimes it can be a small fuel leak. Monitoring fuel pressure can help to eliminate this area.

An easy way to eliminate the MAF issue is to buy a ECU with MAP, IAT sensors (LINK ECU, ViPEC ECU, etc) and dump the MAF's. Then spend the money on a good tune.

Stock ECU can run without MAF's. Also stock ECU rev limit's engine to around 2500-3000rpm when MAF's are disconnected.

AACV is known to fail (or stick) and make engine stall if started. IACV (manual choke on older cars) can cause starting problems too if it sticks closed. Cleaning them sometimes works or replacing them.