Injector Wiring Question

Probaly barely discernible on engine operation. At high RPM and high load, injectors are open 80-85% of the time to provide the required fuel, then they are not really timed to valve opening, they are open much longer than the valve is open. (low pressure) Sequential injection allows mainly to smooth the engine operation at ildle and mid-range but does not make a significant difference at full power.

In any case, to be safe, plug it as initially planned. Simply check from the ECU connector which plug is for which injector. pin 31 to injector 5, pin 35 to injector 6, ...

 

IACV?

 

If you can, check the 02 sensors. Pull a spark plug from each bank, if a bit sooty, and the O2 sensors are over 3 years old you may have one or both mis-reading and being borderline to when they go open/close circuit on their own (eg. the ECU ignores them).

Secondly, ensure your idling valves are working properly (don't know if you are Motronic 2.7 or 5.2, this is for the 2.7) and reset the idle after cleaning the idling screws and the hole they fir it with some carburettor cleaning spray. You should balance the vacuum between the banks.

If you are on a Motronic 2.7, a final thing it to clean out the MAF's and measure the CO screw setting, which should read 393 on pin 1 and 6 with an ohm meter (as it does from Bosch). If the ECU goes open-loop then it reads the CO screws. 393 is quite rich (stoichiometry is around 450-550 ohm)

This is the whole injection system.

The ferrari 348 and up (incl. the 355) have individually timed injectors, that still have discrete timing up to about 9000 RPM. So if you swap cables, you will not cause damage, but feel like the engine runs a bit rough. The fuel will be sprayed on the closed valve instead of into the airstream, reducing atomization and affecting the fueling curve, but will still run a bit rough. If you pull the cable the cylinder will not get any fuel and you'll get a 1/8th drop, which is noticeable at idle and more so as you rev.

Marco

 

Yes injectors are timed with regard to the valve opening but at 9000 RPM and full load they are open MUCH longer than the valve is open (80 to 85% of a complete 2 crankshaft turns for the injectors, while the intake valve is open let's say 40%). So anyway lot of fuel is injected while the valve is closed. No difference in these conditions IMO. In addition, a lot of cars are running great with all the injectors opening at the same time. The difference is may be discernible at idle, may be ....

Tom, have you recorded the OBD data during your cold starts : air temp, coolant temp, ignition advance, closed/open loop status, O2 sensors, MAF, ... Can you see any difference in these parameters when you have a high or low idle?