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SuperBob, Ford Senior Master, Mazda Senior
Category: Ford
Satisfied Customers: 2609
Experience:  18 years Ford, Lincoln, Mercury, Mazda Dealer ASE master, diesel certified. Specialize electrical
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2001 ranger: Changed spark plugs..3.0..plug store

Customer Question

Changed spark plugs on 2001 ranger, 3.0, crossed plug wires, started engine, corrected plug wires, still has miss. Checked codes at parts store, shows miss 5&6. Replaced coil pack, plug wires, still misses.
Submitted: 7 years ago.
Category: Ford
Expert:  SuperBob replied 7 years ago.
HelloCustomer when you say still has miss do you mean it was missing from the crossed plug wires? or do you mean it was missing before you started these repairs and that is why you are putting new plugs in? How many miles on your truck?
Customer: replied 7 years ago.
Ran fine, changed spark plugs and accidently crossed plug wires, of course it missed. Changed plug wires to correct firing order, but now still misses. Took to local Autozone and they checked the codes and showed has miss on 4 and 5. Also check engine light comes on. Tried new plug wires, coil pack and another set of plugs, sill misses.
Expert:  SuperBob replied 7 years ago.
Did you cross the 4 and 5 cylinders previously. perhaps you have crossed more than two. From front to back starting on the passenger side of the coil. list for me where each plug wire is going. Then list for me starting on the front of the coil on the drivers side.
Customer: replied 7 years ago.
At work, will have to do in about an hour on break
Expert:  SuperBob replied 7 years ago.

Meanwhile, I will see if I can get you a diagram to show you the cable routing you can take with you when you check it.

Expert:  SuperBob replied 7 years ago.

graphicPrint this diagram and take it with you, verify the plug wires go to the correct cylinders



Customer: replied 7 years ago.
I'll check and get back to you asap
Expert:  SuperBob replied 7 years ago.
I will be here. Thank you.
Customer: replied 7 years ago.
OK, checked and double checked, and the plug wires are on the right way.
Expert:  SuperBob replied 7 years ago.
What gap did you set your spark plug electrodes to and what brand of spark plugs did you install? Please do not say autolite!
Customer: replied 7 years ago.
Bosch platnim plus, gapped at .45
Expert:  SuperBob replied 7 years ago.
Did you hang onto the old plugs and wires?
Customer: replied 7 years ago.
Yes, tried old stuff and have put 2 new sets of wires, 2 sets of new plugs, new coil pack, same miss, and check engine light on. Also looks like oil gauge fluctuating. Truck ran fine before I crossed wires.
Expert:  SuperBob replied 7 years ago.
Do you have access to a compression gauge, or know somebody who does?
Customer: replied 7 years ago.
Truck ran fine before I crossed the wires, its not a compression problem, and yes I have a compression gauge.
Expert:  SuperBob replied 7 years ago.

At the dealer level we perform tests in accordance with the symptom. I must take your word on the wires and plugs. You say it was fine before, you know you created a missfire with the crossed wires, If the engine sparks the unburnt fuel in the cylinder at the wrong time and forces a valve shut as it is opening or is burning the fuel with and open valve because the spark is lit at the wrong time, you could cause an internal problem. A simple comparison is all we need to verify combustion chamber integrity. check cylinder 6 and 4, look for a 20% or greater difference. All you need to have to run an engine is fuel, spark, compression and air. the coil shares power from three separte coils inside the coil pack cylinders 1 & 5, 2 & 6, 3 & 4. You do not have a miss on cylinders 1 and 2. this tells me the coil is working. four cylinders have air, because they do not missfire, four cylinders have fuel. You say the plugs have spark. Put all this together it leaves the fuel injectors and compression. Odds on two injectors going out at the same time, very uncommon. What do we have left? Compression.

Customer: replied 7 years ago.

The miss is on 5&6, sorry I keep saying 4&5, the test said miss between 5&6. I can check the compression tomorrow afternoon. Does this model have an ignition module like the earlier rangers?

Expert:  SuperBob replied 7 years ago.

The spark is controlled by the pcm. I have attached the workshop manual ignition system overview for you.