Injector missing pulse

[LOve04expedition]

Hi.

I have misfire in cyl#1. I have changed plug, coil and even injector.. still misfire. My car (04 expidition 5.4) also drives on LPG. When LPG are ativated there are no misfires at all.. latest check I ran was with an noid-light.. that do not flash at cyl#1.. I have same voltage at #1 like the other injectors... but on the others the Noid-light flashes. It seems to me that I'm missing pulse at this cylinder.. and out of ideas how to futher proseed troubleshooting.
Anyone had this issue?
(I am from Norway)

 

[TomB985]

I'm not familiar with the differences in configuration with your LPG conversion, but I imagine the injector wiring is very similar. I've attached the wiring diagram for my 04, and it looks like the PCM drives each injector individually. So if you're getting voltage at the injector without a pulse, I suspect you have a failing PCM.

 

[Yupster Dog]

Don't forget to check the wiring harness as well.

 

[1955moose]

If you've got voltage but no pulse, check the wires as the others said. Do a continuity test. I'm betting you've got a broken wire or pin somewhere. You can buy the separate sections of wiring harness for the injectors. Check it out and let us know what you come up with.

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[LOve04expedition]

Thanks, I will try out this.. and hope I dont have to change the PCM.. yet..

 

[stamp11127]

Proceed very carefully. Do not apply power to any wires that connect to the pcm when they are connected to it. If you ignore this warning just make sure your test instrument is approved for use with ecm/pcm.

The pcm should be disconnected prior to checking continuity on the harnesses. Do not pierce the insulation with a probe or you will have issues later on with corrosion. I use small sewing needles inserted into the connector plugs as test points.

A multi meter doesn't respond fast enough to sense the pulses on the injectors or coils. If you wanted to test the circuit pulses with the engine running you will need an oscilloscope.

Diagrams are attached.

 

[John Stephan]

PCM is ground side switched pulse meaning that the pcm grounds the voltage to close the circuit. If your wiring is in tact it's the PCM. This is somewhat common.

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