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Chris (aka- Moose)
Chris (aka- Moose), Technician
Category: Ford
Satisfied Customers: 44505
Experience:  16 years experience
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Put mild cam in 1997 F150 sohc 4.6 romeo engine. After

Customer Question

Put mild cam in 1997 F150 sohc 4.6 romeo engine. After installing, can disconnect injectors or plugs on passenger side of the engine and it does not affect running of engine. Engine does not have the power it should have under load. Compression is good in all cylinders. Changed injectors, did not help. What could be causing this problem?
Lee
Submitted: 3 months ago.
Category: Ford
Expert:  Chris (aka- Moose) replied 3 months ago.

Welcome, I'm Chris (aka Moose) I prefer to work when others don't, I am here around lunch and after dinner till after midnight.

Since none of the cylinders on the passenger side are contributing but compression is fine. This means we need to see if there is no spark or no fuel injector pulse getting to those cylinders. Can you do that?

This is my 1st answer, but does not have to be my only answer. You the website and myself expect you to have a great experience with my help. Please let me know if you are pleased by selecting a star rating above or by replying and saying your pleased. Not rating or rating 1-2 stars does not benefit you nor me in any way. Follow up and reply as often and when needed, there is no extra charge to do so.

Thanks Moose.

Customer: replied 3 months ago.
Forgot to put test light showed injector plugs hot (on) but test light not pulsing as I would expect. Also, spark plug wires are firing. Spark when disconnected from spark plug end or other end.
Expert:  Chris (aka- Moose) replied 3 months ago.

Most test lights can not detect the ground pulse do to the style of the bulb. Do you have a noid light? If it ends up being no ground pulse then the PCM or wiring is to blame.

Customer: replied 3 months ago.
Do not have a noid light. Thought about ground and used my cables to establish a ground. No luck.
Expert:  Chris (aka- Moose) replied 3 months ago.

That leaves the PCM or wiring to the injectors for no ground pulse to those 4 injectors.

Customer: replied 3 months ago.
Could low fuel pressure cause a similar problem?
Expert:  Chris (aka- Moose) replied 3 months ago.

Can a fuel pressure concern cause a misfire, yes, to one complete side of the engine, not likely.

Can fuel pressure make an injector not pulse, no.

Expert:  Chris (aka- Moose) replied 3 months ago.

Hello again Chris here,

  • I am following up with you to see if you got everything you needed from my answer. We're you pleased with my help?
  • If you were not pleased with my help, please let me know by replying so I can help more.
  • This post is coming up on the 7 day mark where it times out. When a post times out, that means it's no longer on my active list (you reply and I may never know it.)

Thanks Chris

Customer: replied 3 months ago.
Cut cats off. All injectors firing except number1. Any ideas? Straight wired ground to injector plug 1, live but not pulsating like the others. Bought a noide light.
Expert:  Chris (aka- Moose) replied 3 months ago.

For an injector to work it needs constant power and a pulsing ground from the PCM. Straight wiring ground to an injector will not help. Are you missing the power or ground pulse? Have you checked the wiring? Have you checked for ground pulse right at the PCM connector?

Customer: replied 3 months ago.
In the morning I will check for ground pulse at the PCM connector. Also, taking one step forward and two back. Rechecked compression and no compression on cylinders 6 & 7. Need to remove valve cover to determine if those rockers fell off.
Expert:  Chris (aka- Moose) replied 3 months ago.

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