1 cylinder misfire??? Black plug...

[endeffect0]

Just recently finished a complete 6bolt engine swap and im using the first gen coil pack with the plugs swapped. When I fist put the car back together I took it for a drive and it ran good with a minor hesitation before it hit boost. Since then iv taken a few mile or so trips trying to work out the kinks and its run worse and worse. Iv been checking the plugs every time and cylinders 1,3&4 come out really lean but cylinder #2 comes out black. I’ve done a compression test and they all come out strong and with similar numbers. Changed out the coil pack with no effect and even swapped injectors between cylinders thinking perhaps one is stuck.
Im out of ideas at this point and I have no experience with turbo cars or DSMs what do you guys think on this one?

 

[Joshewuhh]

You're running rich in bank 2.
Check your fuel spray, fuel pressure, and above all.. the o2 sensors.

 

[Littlebeeper]

mine was doing that on #1. turned out the ecu was going out and would periodically shut off #1 injector for a couple of seconds. i found this by testing the injectors and #1 would fire back up a fter the test with MMcD. this was on a 1G though. Maybe you have a connection keeping the injector open too long or something

 

[tonygk85]

your running rich in bank 2 to like he said

 

[endeffect0]

I agree that it seams like i am running rich on that cylinder but i just cant figure out how after swapping the coil packs and the injectors (and the possibility of it being a oil blacken plug has been in the back of my head even if it is unlikely).

I don't have a way of checking fuel pressure at the moment and i dont really understand how that could affect just one cylinder,(not to say it couldn't just that i cant grasp it).

as for the injectors i thought one of them might be stuck open so i swapped the injector from cylinder 2 into 1 and it didn't change the way the #2 plug came out.

I dont have any way of reading the o2 sensor but my suspicion is that its seeing the over all mixture as rich if i'm dumping fuel into #2 and trying to lean the whole thing out. that would explain why all the other plugs come out lean. makes sense to me, but then again its a DSM and so far nothing has made much sense to me on this car...

Littlebeeper: i have a feeling that my problem is similar to the situation that you described but i don't know how i would test an injector to be honest, ill have to look that up. does anyone know if its likely that the ECU could cause a problem like this. that sounds like the most likely possibility to me.

thanks for the help..

 

[Talesin]

Did you try swapping the spark plug wires between #2 and 3? A bad plug wire on 2 would be the easiest explanation, and since cylinders 2 and 3 are 'buddy cylinders' (as are 1 and 4) they fire spark at the same time, every time they fire. So reversing 2 and 3 won't alter how the engine normally runs, but if the problem switches to 3, you know you have a dead plug wire.

Fuel pressure would affect all injectors, not just one, unless you had one RIDICULOUSLY weak injector that needed replacing anyway.

If you have a mechanic's stethoscope, use that. If not, get a long screwdriver and put your ear against the end of the handle, and touch the #2 injector with the tip of the screwdriver. Listen for if it clicks, and listen to the other injectors so you know what it's supposed to sound like. If it's not clicking, try giving the injector a smack with a relatively weighty tool, in case it just got stuck. The screwdriver mentioned above could work, or a standard 3/8" drive metal ratchet can get the kinetic kick to free up the aperture if it's just gotten stuck in place. Just a good firm tap, don't haul off and bash the crap out of it. (tempting as it may be)
If it's still not clicking and you're CERTAIN that the injector isn't stuck, could potentially be a bad resistor in the resistorpack, an aging injector connector lead (the part that plugs into the injector to give it pulse might not be clipped on securely, with the retainer wire), a broken wire somewhere (likely on the lead), any number of things. Get a noid light (or just a cheap LED with the resistor already on the proper leg) and plug it in where the injector would normally go, electrically speaking. Run the car, watch for the light to flash. If it flashes, you have signal and the injector may be the problem. Also check inside the fuel rail for any blockages if you haven't. If the light doesn't flash or stays solid-on, you have an electrical problem, not a mechanical problem.

Never heard anyone refer to cylinder 2 as 'bank 2' before. Usually bank 1 and 2 are for V6 or V8s, to distinguish between sides of the engine for carb or TB tuning on individually-controlled manifolds (as opposed to a single throttle body, like on ours).

Only the front O2 sensor matters as far as running right. The rear sensor is just there for ODBII sensing if your cat is going bad. It'll throw a CEL, but it won't affect how the car runs.


I'm assuming you've got NGK BPR6ES spark plugs installed, and properly gapped?

 

[endeffect0]

Did you try swapping the spark plug wires between #2 and 3? A bad plug wire on 2 would be the easiest explanation, and since cylinders 2 and 3 are 'buddy cylinders' (as are 1 and 4) they fire spark at the same time, every time they fire. So reversing 2 and 3 won't alter how the engine normally runs, but if the problem switches to 3, you know you have a dead plug wire.

--- i have replaced the plug wires and the coil packs but still swapping the plug wires between 2 & 3 is easy enough and ill try that in a few mins, cant hurt to be extra sure...

Fuel pressure would affect all injectors, not just one, unless you had one RIDICULOUSLY weak injector that needed replacing anyway.

--- thats what i thought, and given that i have swapped the injectors between cylinders 1&3 with no change in how the plugs came out i assume it wouldn't be a problem, mechanically anyway, with the specific injector...

as for the rest of it, i am using properly gapped spark plugs and i have been swapping them between cylinders every time i check the plugs to keep from any possible carry over in the results.

I am throwing a CEL but i don't see how that would affect one specific cylinder if it was an o2 sensor so I've been ignoring it till i get this nailed down..

im about to go put the rest of my newly quired wisdom to good use, you have been incredibly helpful Talesin, thats just the kind of information and knowledge that i needed and would have otherwise not been able to find...