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Ron
Ron, ASE Certified Technician
Category: Ford
Satisfied Customers: 23001
Experience:  23 years with Ford specializing in drivability and electrical and AC. Ford certs and ASE Certs
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2002 ford f150 5.4 runs rough and missfire replaced

Customer Question

2002 ford f150 5.4 runs rough and missfire replaced manifolds intake manifold and cleaned tb
Submitted: 2 months ago.
Category: Ford
Expert:  AZTechBrian replied 2 months ago.

Hello. Do you know which cylinder is misfiring?

Customer: replied 2 months ago.
it was po301 so i worked there but found my intake manifold
was leaking a bit so replaced that had po174 also
Expert:  AZTechBrian replied 2 months ago.

P0174 is a bank 2 lean code. P0301 is a misfire in cylinder 1 which is in bank 1, so they shouldn't be related. I assume that the injector and coil that you had replaced were both on cylinder 1? Have you tried a compression test to make sure that the misfire isn't the result of poor compression in that cylinder?

Customer: replied 2 months ago.
Not yet no and I had the po301 first changed the coil and injector then got the po174 and put a little water around intake it changed noise at idle so replaced the intake now no code just running rough and won't even up high
Expert:  AZTechBrian replied 2 months ago.

You changed the injector in cylinder 1?

Expert:  AZTechBrian replied 2 months ago.

did the condition get worse after replacing the intake gaskets?

Customer: replied 2 months ago.
No idles better but the same you rev up its slow on misses and if I rev to 4 k at idle it will return miss more
Expert:  AZTechBrian replied 2 months ago.

Ok. You cleared codes I assume, and the cylinder 1 misfire was all that returned?

Expert:  AZTechBrian replied 2 months ago.

the fact that it idles better indicates that you probably had a vacuum leak which was probably repaired when you replaced the intake gaskets

Customer: replied 2 months ago.
Ya but I have no codes right now and runs very rough and miss fires under acceleration or revving it up
Expert:  AZTechBrian replied 2 months ago.

Ok, then you have a code on it's way very shortly. I am sure it'll be another cylinder 1 miss. I would check compression in that cylinder right away to rule low compression out. You have already addressed the other causes of a misfire.

Customer: replied 2 months ago.
Ok will do
Expert:  AZTechBrian replied 2 months ago.

Please let me know how the compression looks.

Customer: replied 2 months ago.
162 on 1
Expert:  AZTechBrian replied 2 months ago.

Sounds good to me. If your compression is good, and your spark plug and coil are good, and your fuel injector is good, then have you verified that your fuel injector is getting power?

Customer: replied 2 months ago.
no i dont have a noid light
Expert:  AZTechBrian replied 2 months ago.

I would check that. alternatively, If you have a mechanics stethoscope then you can listen to the injector to see if it's ticking. We are running out of options here.

Customer: replied 2 months ago.
drove the truck got a po174 code if changed the forward o2 sensors not long ago. Not the aft ones
Expert:  AZTechBrian replied 2 months ago.

still a lean bank 2 code. No misfire code anymore? What is your bank 2 fuel trim?

Customer: replied 2 months ago.
No idea my reader is not going that far
Customer: replied 2 months ago.
No miss fire code yet
Expert:  AZTechBrian replied 2 months ago.

It runs bad at idle and at the higher rpm as well? or clears up at higher rpm?

Customer: replied 2 months ago.
Bad at both no power at high rpm and barly climbs
Customer: replied 2 months ago.
Worse as rpm goes up
Expert:  AZTechBrian replied 2 months ago.

Ok. You have more codes on their way. If your only misfire codes from before are cylinder 1, I would suggest checking for injector pulse. You could also do a power balance test where you unplug fuel injectors one at a time while the engine is running to see which one or ones make no difference in the way it's running. Those would be the misfiring cylinders.

Also, if you let it sit for a while, does it run fine when you first start the engine, then get worse as time goes on, or does it run horrible right from the start even after sitting for a bit?