J30 Injector/Coil Pack

[Mayhem_J30]

On a 93 J30 will a CEL illuminate when an injector or coil pack fails?

The J started idling very rough yesterday. You can see the whole car shaking. With some throttle it feels like a cylinder is dead. The exhaust pulses on the passenger side tail pipe are only have as strong as the drivers side. Crude method, but I think it gives me a lead on which side to start on.I'm going to try to do my own power balance test w/o a consult by pulling wires to injectors one at a time. After that I'm going to get some Ohm readings from the injectors.

Anybody have any tips for me?

[Mayhem_J30]

With thanks to Ned at Stein Automotive and his stethoscope we've narrowed it down to the #6 Fuel injector. Figures it would be the one hardest to get to. :rolleyes

[Mayhem_J30]

Update: The stethoscope sure saved a lot of time of going through each one of those injectors and doing an Ohm test. I tested #6 injector and it was 24 ohms; way out of the spec range of 10-14 ohms.While I was in there the coil packs were all easy to test. Luckily they all hit 0.9 ohms dead on! So all of those are still in good shape.I've got Scottsdale Infiniti hooking me up with a new injector. Thanks Joe! And hopefully I can get this thing out and back in without having to pull the plenum (crossing fingers). The twin turbo Z guys have metioned using a dremel tool around the upper manifold to help get the injector out. I assume it'll be very similar on the J30. If I can get this done without taking off the plenum I'll save tons of time and cash. Too bad #6 is in the hardest to reach spot. Lots of wires back there. I'll keep you guys posted. I've never replaced an injector on a VG before.

[DAEDALUS]

When coils fail, often they ohm fine because the wiring itself is OK. The problem is that the insulation begins to go, and the coils will begin to arc while you're driving. Doesn't happen anywhere near as often as injector failures, but it does happen. Just be aware. Arcing at the coil usually leaves tell-tale signs on the plugs. Don't forget to bleed the fuel pressure in the rail before removing the injector.

[Eswift]

yeah, the fuel pressure will really mess you up.. i would wear safety glasses just in case.

you will either need to dremel, or remove the plenum. luckily the J30 balance tube makes things easier to deal with. might help to remove or swing back the hood, its pretty tight back there.

at my injector failures, i believe the CEL came on... and there was definiltey the injector ohm code in the ECU. right on with the stethescope! thats the way to do it! ( a beer bottle works nearly as well)

good luck, ive never had a 6 myself!

[DAEDALUS]

I know for the Q, the injector has to ohm really high for it to throw a code. I've meaured about 50 ohms on an injector (harness) without the CEL coming on.

[Q45tech]

The 90-95 ecu are dumb as rocks when it comes to self diagnosis of sensors............other than opens or shorts.Outputs like injector open time and applying current to coils are just done and not checked because there is no direct way to see that something actually happens.

How do you monitor a plug firing or an injector squirting without introducing a level of complexity similar to OBD2.......The engine wouldn't be smooth if you were constantly doing a power balance ========running on 5 or 7.

OBD2 uses the O2 sensors and a powerful computer to analyse each cylinders resulting A/F ratio at least during idle and cruise......a misfire will make the mixture richer for the small time period when the exhaust valve is open.......if the injector works and the plug does not fire and the exhaust will be extra lean when the injector does not work.

[Mayhem_J30]

Well using the dremmel worked! WOOHOO! Next hardest part, pulling the injector out. I've yanked and yanked and now there isn't much left of the top of the injector. Soaking it with Liquid Wrench right now and maybe by tonight it'll come out. I can turn it, but it won't budge to come out. If this thing doesn't come out I guess I'm gonna learn how to pull the plenum. The learning and time I got it's the extra money involved when pulling the plenum that the problem. {keeping fingers crossed}

[Mayhem_J30]

Got that biatch out yesterday! Soaking it with the Liquid Wrench over night must have done the trick. Put in the new one, which looks a little different, put her back together and she fired right up and was smooth as butta.I took pics while doing it so I'm going to attempt a write up.

[Eswift]

sweet!

[VimyJ]

sweet!

Ditto