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Edward
Edward, ASE Certified Technician
Category: Ford
Satisfied Customers: 2768
Experience:  ASE certified. Auto Transmission rebuilder for Ford Motor Co. from 91 to 2000
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99 e150 4.2l has a random intermittent misfire. I have

Customer Question

99 e150 4.2l has a random intermittent misfire. I have already replaced the coil pack, wires, plugs, and number 3 injector because that's what the code showed at first. So after doing the injector I did a cylinder contribution test and it is showing that numbers 2,3,4,5 are all misfiring at random times, they never miss at the same time. Any ideas?
Submitted: 1 year ago.
Category: Ford
Expert:  Edward replied 1 year ago.

Hello, Eddie here and I will do all I can to help. Are you now receiving misfire codes? such as P0302? P0303 etc. ? What codes are you getting now after coil pack replacement? or is it setting any?

Customer: replied 1 year ago.

It isn't throwing any codes. That's part of why I'm confused

Expert:  Edward replied 1 year ago.

Alright, It's running bad all the time now? or just occasionally? You double checked the firing order and made sure you had the wires on correctly when you replaced the coil pack correct?

Customer: replied 1 year ago.

I did double check the wires after everything was done. It does it all the time but only a few rpms above idle and it starts shaking but then smooth's out with higher rpm. Any time above that lower rpm area and it's fine

Customer: replied 1 year ago.

Am I looking at a bad pcm or could it maybe be going out?

Expert:  Edward replied 1 year ago.

That is a high possibility, there are coil drivers in the PCM that do go bad, and the only thing between the PCM and the coil pack itself is a wiring harness. If that harness is good, and it is misfiring, I would likely try another PCM if it was mine, Make sure you don't have any vacuum leaks, one hose is bad to crack near the EGR valve at the end. You should be able to hear it if it is, or spray some carb cleaner around the intake when it's running and and then it runs good when you hit the leak with carb cleaner and the engine speeds up noticeably. Keep in mind you can't just swap a used PCM on this model, it has to be programmed. It is that way due to the Ford PATS system with the chip in the ignition key. a mobile locksmith will usually do this for minimal charge and is much cheaper than the dealer. Let me know if you have any further questions.

Expert:  Edward replied 1 year ago.

Hello, Following up with you, Any luck with it?