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RJ
RJ, Ford Technician
Category: Ford
Satisfied Customers: 1574
Experience:  Ford senior master and ase master certified 19years Ford dealership experience
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2001 F-150: apparently has a misfire on one cylinder..coil..replacing

Resolved Question:

My 2001 F-150 apparently has a misfire on one cylinder. The dealer and two seperate mechanics say they're not sure of the problem (plug and coil have already been replaced but still no fire).
The mechanics tell me it's better to replace the engine since it has about 150,ooo miles. So, the problem has not been identified but three mechanics all told me I'm better off replacing the engine. I don't want to spend $5000 can you help?
Submitted: 5 years ago.
Category: Ford
Expert:  RJ replied 5 years ago.

RJ :

Hello Thankyou for Choosing Just Answer.

RJ :

Are they able to tell you which cylinder is missing ? Have they performed a manual compression test ?

Customer:

The compression test is fine they say. Not sure of the cylinder number but it's the 3rd from the fire wall on the passenger side

Customer:

So what do you think?

RJ :

That would be number two cylinder. Is this a miss all the time or just sometimes ?

RJ :

Verifiying engine integrity is first and formost in determining the failure here. If a compression test is ok then a engine replacement is not likely needed ?

Customer:

Pretty much all the time. One of the mech's said the valve may be stuck or have a broken spring but he didn't recomend any solution.

RJ :

If you have a valve train issue this would show up by doing a vacume test and if the gauge bounces during the missfire then you would need to inspect valve springs.

Customer:

Can this be repaired without removing the entire head?

RJ :

Broken valve springs are not uncommon , but they dont break often

Customer:

I don't know if I have a valve train issue or broken spring. What do you think?

RJ :

Yes a quality tech could replace a broken valve spring with the head installed as long as the valves are sealing and the compression is ok. When i say valve train i am refering to the valves, valve springs, tappets etc.

RJ :

Performing a vacume test and verifying compresion is what i would do first. I would also swap the fuel injector to another cylinder and verify the miss stays on cylinder 2 .

RJ :

We have certainly had more injector failures then valve spring failures.

Customer:

The ford dealer charged me $110 to evaluate the problem and said they were not sure of the problem and would have to open-up the engine to do more evaluation. The fuel injector has alreday been swapped out and determined to be fine.

Customer:

Is there anyway to determine what the problem is without spending abunch more money?

Customer:

I wonder why the dealer didn' do the pressure/vacume test?

Customer:

Assuming one of the other mechanics did a vacume test but still recomended engine replacement, what would you do after the vacume test checks out OK?

RJ :

Everything cant check ok , it just dont work that way ! If the have done all the tests and there is a verifable missfire then one of these tests would show a fault. Maybe something is being lost in the translation between you and the tech. I would not based on the info you have given me advise dissassembly of your engine. One of these test would have to indicate a fault.

RJ :

The only other test would be a cylider leakage test , but this is normally done when a compression issue is found, this would allow one to determine if the low compression was caused by valves, head, or if the concern is in the piston , cylinder area. Then tear down would be required , or i may advise on a complete do to miles.

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