Dead Injectors 4 and 6?

[MIB]

I have been experiencing a misfire. I have high BLM's @160. I can bandaid it by raising my fuel pressure from @44 PSI to lower them. I have replaced all hoses. Checked the exhaust, EGR, check valves, throttle body, PCV, CCI, coils. I have sent the ECM to Bob to have it tested. It's fine. I have found that when I move the 2 injectors plug over to 4 or 6 the motor does change pitch. It also changes on 1,3 and 5. I just pulled my injectors to have them cleaned. Any and all help would greatly appreciated.

My combo:
.30 over 109, JE's, ported irons, 70BB, 208/208, 72's, FM, TPlus, single shot, etc.

 

[SouthernCal GN]

Change the injector harness- over time, it (like everything else) becomes brittle and decays.

 

[MIB]

Change the injector harness- over time, it (like everything else) becomes brittle and decays.

Thanks I replaced the harness over a month ago with a RACETRONIX.

 

[turbows6]

Is the problem continuous or intermittent? I would think if it had 2 dead cylinders the engine would barely run at all. I'd clean all the connections with electrical cleaner and inspect the connector going to the injector harness for any damage. How do the plugs look? do they look really lean on 4 & 6?

 

[BlackBandit]

Do you have a node light?

 

[DynoTune]

If you don't have a noid light, check this -

With the injector plugged in, key on, engine off you should have power on both wires (power to the injector from fuse on one side, and power through the injector on the other side) The PCM fires the injector by grounding one side of the injector.

You can try back probing the signal wire from the pcm with a low impedance test light, but it may not be fast enough. Your test light should blink with the engine running, and the injector plugged in. You may need to pick up a noid light to see this, they are cheap at most auto parts stores.

If you are getting power, and the injector is getting a signal (ground from pcm), you can pretty much figure it's the injector. If you missing either the power or ground signal, time to look at wires.

 

[MIB]

Is the problem continuous or intermittent? I would think if it had 2 dead cylinders the engine would barely run at all. I'd clean all the connections with electrical cleaner and inspect the connector going to the injector harness for any damage. How do the plugs look? do they look really lean on 4 & 6?

Continuous problem. I don't think the 2 cylinders are completely dead. I inspected and cleaned all pins and cables. My plugs are wet but dark after the latest plug change so I know it's not real lean.

 

[MIB]

Do you have a node light?

Yes, I am firing at least to the harness.

 

[DynoTune]

My plugs are wet but dark after the latest plug change so I know it's not real lean.

If they are wet, your getting fuel from the injectors, I'd be looking at the ignition system a little harder... Do these two cyl's share a coil (My Buick is at the shop right now, and I can't remember the cyl. pairing on the coils)

 

[MIB]

If you don't have a noid light, check this -

With the injector plugged in, key on, engine off you should have power on both wires (power to the injector from fuse on one side, and power through the injector on the other side) The PCM fires the injector by grounding one side of the injector.

You can try back probing the signal wire from the pcm with a low impedance test light, but it may not be fast enough. Your test light should blink with the engine running, and the injector plugged in. You may need to pick up a noid light to see this, they are cheap at most auto parts stores.

If you are getting power, and the injector is getting a signal (ground from pcm), you can pretty much figure it's the injector. If you missing either the power or ground signal, time to look at wires.

I am going to double check everything and try to figure out what I did last. This problem started after I installed the injectors, hot-wire harness and turbo from my other car which also had a misfire (wiped cam). I know it's either in the harness to ECM or injectors. The injectors are being cleaned so that will eliminate 1/2 of the equation. Thanks I appreciate all help and am open to any other suggestions.

 

[MIB]

If they are wet, your getting fuel from the injectors, I'd be looking at the ignition system a little harder... Do these two cyl's share a coil (My Buick is at the shop right now, and I can't remember the cyl. pairing on the coils)

I wish . No they don't. I have tried 3 different coils packs and ignition modules. All tested good with caspers tool. Car sounds strong in the midrange. I know it's not right though because it has never knocked 16 counts up top.