Running On 5 Cylinders (not Coils)

[l6a6w6s6]

Hi everyone,

the car is a near stock (cat back exhaust and POD) a31 Cefiro, factory manual RB20DET. I've just changed the motor for another from a wrecker because the old one cooked and had very bad compression. I purchased an automatic spec a31 rb20det (but with clutch/flywheel on back), but switched over the loom, ecu, sensors, injectors, coils, plugs, ecu, flywheel, box, etc. Previously the old engine with these parts ran fine apart from being gutless and overheating.

Now the engine seems to be running on 5 cylinders. It sounds like a wrx and unplugging the coil for cylinder 1 has no effect. I switched coils and plugs for cylinders 1 and 2 and the problem remained for cylinder 1 only, leading me to believe the coils and plugs are ok.

I then unplugged number 1 injector plug, which made no difference to the running of the engine. Multimeter at the loom plug for this reads 0.7volts while running so I figured I had a busted injector.

Switched it for a spare today and it made no difference. This fresh injector clicked with 12v applied so it shouldn't be seized.

I ran the eccs diagnostics and got code 54: Signal Circuit From A/T Control Unit To ECM which puzzles me. The car is factory manual with the same electronics as before, so why would it be telling me it wants an auto signal? Only thing I can think of is that I've missed a plug somewhere switching the looms, if so where might it be?

Anything else I can try?

I hope people don't just dismiss this as another coilpack fault without reading because I'm sure it's not from my tests. Thanks in advance for any assistance, this has me stumped

Edited November 10, 2005 by l6a6w6s6

[blind_elk]

I wouldn't worry too much about the ECU error code right now.

It would appear that one of the wires to #1 injector has a break in it somewhere. Use your multimeter to check continuity of the wiring. 1 side will connect to the ECU (possibly pin 101). The other side is +12V when the IGN is ON.

[l6a6w6s6]

So the injector fires by having a constant 12V but is only grounded by the ecu at the proper times. Ok will test ecu pin cheers for the help.

[l6a6w6s6]

Ok, did some tests. Both injector wires measure 12v when ignition is ON and no engine running. Tested continuity for pin 101 (white with silver dash) and it matches one pin of injector plug, pin 109 (white with black stripe and silver dash) matches the second injector plug.

I've also tried two different ecus, one an a31 manual and the other an a31 auto and the car runs exactly the same with each, and also they both give diagnostic code 54.

Any more help is appreciated.

[RB30-POWER]

Have you actually tested spark output from Coil/Cyl 1?

If you don't have spark it will be a faulty ignitor module (on top of cam cover at rear of motor).

The ignitor module has a transistor for each cylinder that switches the coil on and off for spark! So if the transistor is stuffed for Cyl 1 it will never spark.

It could also be a faulty/broken wire that goes into the module as well for cylinder 1.

If you measure +12 on both sides of the injector plug i would say the injector drivers are fine. (To confirm injector operation, its easiest to measure the duty cycle (with capable multimeter) of the injector whilst running, to confirm its opening)

[l6a6w6s6]

I've run the engine with the coil disconnected from the spark plug hanging out to view, with number 2 along side it to compare. Both sparked so I assume that meant they were ok and the ignitor channels as well.

I just did another test, plugging in spare injectors into the loom whilst the engine was running (injector just loose/not in fuel rail) and could get any to make a sound.

Could the ecu be purposely cutting cylinder 1 because of the code 54?

Edited November 11, 2005 by l6a6w6s6

[RB30-POWER]

You can put a test light or test led onto the injector connector and see if its actually pulsing?

[l6a6w6s6]

Ok just did that and I have an identical looking pulse for injector plug numbers 1 and 2. Cylinder 2 is still working fine so I assume the signal to the injector is fine too.

[RB30-POWER]

Hmm, you have injection and spark, but only running on 5.

Maybe there is a big hole in the piston and no compression?

Sounds stupid, but are the plugs from the wiring harness connected to the correct number injector and number coil? Usually there is enough wire length for cylinders that are side by side to be put on back the front.

Edited November 11, 2005 by RB30-POWER

[l6a6w6s6]

Ok so all of a sudden it just starts working. I knew the plug was getting pulse

but wasn't sure if the injector was firing or not (rtoo much vibratio and noise t hear or feel the click. So I took the cas out of the head but still plugged in, and rotated it with the ignition on. The number 1 injector definately clicked then. Even so I decided to change it back to the original one which I tested with some direct 12v, clicked on command as well. Switched them over and then it just fired up properly like nothing was ever wrong. Unbelievable but true, this is with the same initial components with what the problem started.

Car running well now except for a slight miss as it hits decent boost, but that's not to worry I'll put it on the dyno this week just to check the mixtures and what not. Thanks to everyone who posted with ideas your help is much appreciated. Special thanks to BHdave for some solid time going through everything with me on ICQ.