99 2.2 no fire on #2 cylinder

[trox]

Stumper for the crowd.... I have a 99 S10, 2.2 with about 250 miles on the truck and 50K on a remanufactured engine. Out of the blue it started to misfire and I found #2 cylinder not to be firing by pulling the plug wire and getting no difference in performance. I pulled the plug and found it dry but black and sooty. Put a new plug in the hole and changed the wire and also checked the spark with the old plug and while running it has good spark. Started to think it was the #2 FUEL injector so I swapped the #1 and #2 injectors and the problem is still on the #2 cylinder. Now I’m at the point of checking for correct power to that injector. Can anyone tell me what I should see there? Is it power all the time with a timed ground from the computer? I checked the connector at the back of the engine that I think connects to the fuel injectors and I have power when cranking and running on one wire (white I think). Can I check there for a timed ground? Any help on this one is much appreciated. I just sold this truck to my Son in-law so I take responsibility for it at least for a little while.

[Blue Bowtie]

All the injectors get their voltage supplied via the common source pink wire from Fuse 10 (20A) in the UEC. Splices are in the injector harness/loom to distribute this 12V power. The individual injectors are grounded in sequence by the PCM, terminals A2 (Cyl 3), A7 (Cyl 4), B10 (Cyl 1), and B11 (Cyl 2).

For reference, it IS safe to intermittently ground the grounded side of the injector to test their function without fear of damaging the PCM, since the PCM switched these lines to ground as part of normal operation.

If you ground B11 does the injector fire? If you connect a test light across +12V and B11 does is flicker while the engine is running? It may be that the PCM sinking output transistor is damaged or has poor connection internally or at the header connectors - Unseating and reseating the connector can help wipe them clean.

[trox]

Thanks Blue Bowtie. I guess my dirty White wire is actually pink.Do you know the wire color of the B11 pin from the PCM? I swapped PCMs already and got the same result. Sorry I should have mentioned that. I should be able to check the ground at the same connector at the back of the motor that connects to the injector harness. If I don't have the intermittent
flashing light from all the other pins my main harness is bad. If I do have flashing light at all pins, my injector harness could be bad. I can try to get the harness off the #2 injector from under the intake since I've had it off once to do the swap between 1 and 2 injectors.

[Blue Bowtie]

Trox - That's good information. Your wire is probably gray, not pink. That helps define the system you have. In that case, the #2 injector driver wire should be light green/black (with a black tracer). #1 is black, #3 is pink/black, and #4 is light blue/black. All the +12VDC feeds are gray, and the feed is from the fuel pump relay source. Obviously, you have +12V on at least three of the injectors.

If something is wrong with the PCM or harness I would expect that you would see a test lamp flicker on all the injectors EXCEPT #2.

[trox]

Thanks again Blue Bowtie, I'll post what I find.

[trox]

Well I've put my test light across the two wires on the injector connector. Cranked the motor over and I got a pulsing light! Now what the heck???? I have spark at the plug. I've swapped injectors. I have checked continuity of thr grey power wire and the green with black tracer from the injector to the main connector behind the . V throttle body. Swapped pcm, changed plug, replaced plug wire. Anything I'm missing?

[Blue Bowtie]

Is there compression on the #2 hole? There could be a valve issue or something else preventing power production in that cylinder. If the exhaust rocker for #2 has slipped off the valve, a push rod is bent, or a stud pulled it might explain a lack of power output even with fuel, spark, and no other "normal" cause.

Slipped rockers and pulled studs happen in Chevy 60° V-6s fairly regularly, and create the same symptoms, and the design of the 134 inch four is not substantially different:

[trox]

I checked #2 compression and 150 right after swapping injectors. I can look at the rockers next. Thanks again

[trox]

The rockers are rockin. Everybody tight and looking good under there. Seems to be getting worse maybe. If I get a scanner you think I can see anything in real time?

[trox]

Bingo!! The thought crossed my mind that when I was checking the spark I had the plug laying on the motor but not necessarily grounded. When I cranked it the motor started and the plug had good spark. I thought I'd make sure it was grounded with a jumper cable and sure enough No Spark! Swapped out the 2-3 coil pack and it fired up good. Not 100% but waaaay better. Cleared my P0300 code with the scanner I just bought and drove a couple miles. Still have a miss but then P0300 means multiple missing cylinders. After a mile or so I got P0301 for the number 1. So I changed out the 1-4 coil pack (I had 2 sets sitting around for an old hard to start issue I've learned to live with. (pedal to the floor works every time) Thanks Blue Bowtie for the help on this. I was about to get crazy and pull the fuel rail again and extend a harness to watch the injectors shoot.

[Blue Bowtie]

Sorry about the long way around, but you DID mention that you had good spark.

At least, NOW you do. Way to stick with it!

[trox]

I always thought you would have no spark without a ground but in this case it did have spark without the ground and with ground it had none. I just assumed it was getting its ground sitting on the valve cover because I saw a good spark.
Thanks for staying with me on this