C33 Laurel RB20DET running rough...

[kumasan616]

well I got the thing running and idling (after cleaning out the AAC), although it runs rough/misfires at all RPMs and wants to stall until warm. could be a set of bad plugs, coilpacks, or what? Any ideas? The motor is pretty much stock except for Air filter and intake piping , 3 inch exhaust, and possibly a slightly tweaked turbo (not sure yet).

[jdmae86]

if it turns out to be an ecu prob... i have a rb20 ecu fs... more than likely its not

check the timing?

[kumasan616]

I think its not a timing issue, as the CAS is installed correctly... I think I have it narrowed down to one of several causes:Likely:-not getting 12v (could be an old battery, cranks fine but runs rough)-bad coil/s or plugs-going bad ignitor-bad grounding (ground wire going from harness to ignitor mounting bolt -on coilpack cover is old and may be inadequate)Less likely:-fuel pressure (seems fine but I need to test it to be sure)-injectors (maybe one isn't firing/dirty, although I don't think this is the case b/c plugs are coming up fouled on cylinders that are not sparking)-compression bad (getting done this week)-bad ECU-bad CAS (seems to work fine, it passed the "clicking" test)

Any other ideas? I did test the spark by laying all 6 coils with plugs out and spinning the CAS to check for spark and 2-3 seemed at random to arc outside of the coil pack boots and onto the block of the coilpack...

[nizmo zilvia]

Mine did the same thing until my CAS died. Timing was all over.

[kumasan616]

I'll test it out tonight with the other CAS I have lying around, although when it idles, (albeit rough with misfiring) the idle does not jump all over the place as expected with a dead/dying CAS. I think I'm gonna try a new battery, test the alternator, and change the coilpacks with the spares I have along with RTVing the coil pack boots... gotta make sure the spark is going in the right direction!

[kumasan616]

UPDATE: I did a compression test, all cylinders are between 145/155 with no leakdown so that's all good. I then did a comprensive test on the coilpack harness, testing each coilpack on each harness plug, and each coilpack on each plug. All good, a little weak spark through the current plugs, but good. I cleaned the plugs, regapped them, it helped some but on one or two the electrode was a bit worn/sparking poorly so I changed the plugs to Z32 300ZX TT Bosch platnum plugs, cleaned up the intake a bit and IT RUNS! Rough idle (sounds like a WRX engine at times), still trys to stall when cold, but spools/revs freely once past 2000 RPM on all 6 cylinders.

Next t I am going to test/do the following:-Timing-CAS (I have a spare)-ECU codes-voltage of charging system (cranks nicely but may not be producing enough voltage to coils)- maybe new battery/alternator-fuel pressure (pulling the vacuum line to the regulator to see if I get any change in running)-change fuel filter-injector test-AAC is good, but need to check/clean the IACV (the other element under the intake that works with the AAC)-double check all intake piping, SMIC, and vacuum lines-replace any leaky heater hoses, radiator hoses (found 1 so far)-replace belts-remove or rebuild A/C system (its there but not sure if its worth the effort yet, as it has kinked A/C lines that are hard to replace)-clean up any errant wiring-replace/rebuild water pump, P/S pump, Alternator, etc.

[kumasan616]

Another UPDATE: Found out I had the wrong MAF on the car... turns out the one I had on there has a purple tag, and the correct unit should have a green tag (for RB20). Plus as soon as I pulled the harness connector off of the MAF the car would die, which indicated that the MAF itself was bad/wrong for the car. Bad news was the shop was fresh out, so they have one on order along with my laurel hood emblem which someone swiped while at the shop, so I get to wait until they arrive...