I keep getting a #7 injector improperly functioning code. I swapped the #5 injector with the #7 and cleared the codes. I drove it around a few minutes and the code came back as still the #7. So, I know the injector is working. Next, I checked to see if power is getting to the injector and that was good. Next, I traced the signal wire back to the pcm and I have continuity in that wire. Unless I am missing something, the only thing left is that the pcm is not controlling the #7 injector. Right? This problem just started happening all at once. I was just driving down the road and it started running like crap. It is missing bad, it idles at about 550 rpm's, and it is running crazy rich. Does anybody have any ideas? Sorry so long. Any help will be greatly appreciated.

 

update.....
it is still running the same with the #7 injector improperly functioning code, but neither of the back two cylinders are running. After its running for a couple of minutes, I can touch the #7 and #8 header primaries and they are cool. The others are too hot to touch.I checked the voltage to all the injectors and they are good. I pulled the fuel rail up enough to see if they are spraying and they all are spraying just fine. I would like to put a noid light on them but I don't have one. Thay are spraying in sequence so it must be working. Also, I checked the spark on all 8 cylinders and they are all firing too. WTF is going on? Is it possible it could have jumped a tooth on the timing chain? Does that even make sense? Anybody please help.

 

First, start by changing out the 7&8 spark plugs, and ohming out the plug wires. If you've got fuel and spark, there's no reason not to fire other than catastrophic stuff. Well, there is one other possibility, but I doubt if you got a bird a rag or small child down each of those fuel/air runners, I could understand one but not both:O) As far as noid lights go, you can easily make one from just a few radio shack parts

Hope all goes well

 

How do the plugs look? How many miles do you have on the motor? Over 70K already? If you've got a compression gauge, check the compression. With 2 adjacent cylinders down I'd look at a head gasket leak. I'd also get some CR electronics cleaner and be sure all of the contacts are good. Also, a little bit of ohm difference in resistance can mean a big difference with the pulse width of the injector.
Also:
1. Check plugs and wires, anything loose? Change the plugs as mentioned.
2. Swap a coil around to see if you have a coil issue.
3. Bad injector wiring

If anything, check back and let us know what you have found.

 

63k miles. Plugs, wires, cap, and rotor are all brand new. It is the #7 and #8 cylinders. They are the back two on the left and right bank. Now the thing won't even start. I am still getting spark and fuel to each cylinder. I haven't measured the compression yet but I do know the back two cylinders are getting good compression. I took the plugs out and turned it over. I am trying to locate a pcm right now just to test that theory. Does anyone know if I can pull a stock pcm out of another one and stick it in mine? Or does it have to be programmed to the specific truck? Thanks for the replies so far. It has been a big help

 

I just found out that these pcm's have to be flashed. I can't just use one for test. Anybody know of a way to test the pcm without replacing it?

 

I'm guessing you have the 5.9L motor? I'd also check the intake plenum gasket. It is known to leak and casue problems on this motor. Do a search for 5.9L plenum gasket in the 2nd gen truck section. I'd also clean out the TB.

 

yes it is the 5.9 bored and stroked to a 402. The intake gasket just got changed so I am aware of the problems they have. The TB still looks brand new so that should be ok. I still can't figure out why it won't even start.

 

Check compression and look for a leaking head gasket.

 

Are you absolutely sure you are getting fuel flow from the #7&8 injectors. Recently a little problem came to light about the injectors. Occasionally, the inlet screens get plugged with rust, ie no fuel. Since those are on the back of the runners I believe, it might be possible. The solution is to pull them out and simply clean them, but to prevent it from happening again, the rails have to be replaced with an upgrade to the tune of 350 bucks.

Hope this helps--good luck!