OT - Ford V8 coil pack problem

SteveF · Jul 18, 2019

F-150 4.6L V8, coil pack is F5LU-12029-AA. Two on the truck each with four plug wires.

So I'm getting a misfire and check engine light. OBD reader shows an "Ignition Coil #1 problem". Order two Motorcraft ones from RockAuto which arrived today. The Chilton manual says they should test at 12.8 - 13.1 Kohms between TopLeft and TopRight and between BL and BR. These test around 13.7 - 13.9. Checked with my neighbor's multimeter to make sure it wasn't a testing tool problem, same numbers.

Went and looked up RockAuto reviews - Holy Crap, mostly bad.

Since these are out of spec in the box I think the smart move is to send them back.

Anyone have any opinions on who makes some decent aftermarket ones or on RockAuto in general?

Thanks.
Steve

crossthread · Jul 18, 2019

Repair manual voodoo:

The Most Useless Ignition Coil Test

"In my experience, testing the continuity (of the Primary and Secondary circuits with the multimeter in Ohms mode) of the ignition coil has never ever helped me to diagnose a BAD ignition coil. But testing them on the car and in action with the HEI sparker has been THE guaranteed way of finding out if it's good or bad.

Sometimes I've wondered if this testing method (testing the Primary and Secondary resistance) is some sort of cruel joke on the part of the technical writer who wrote the Repair Manual because of the utter uselessness of this type of test. So, in this article, we won't be exploring this testing method at all."

I have an F-250 that spits spark plugs out of the head when it damn well feels like it. I eventually fixed the problem by installing time-certs in the cylinder head. Needless to say, when the spark plugs launched themselves, they took out the COP. I have replaced them with Advance Auto and Rock Auto units and they worked fine.

Garwood · Jul 18, 2019

I've probably spent $100k with rockauto in the past decade. I don't think I've ever had an issue that wasn't resolved super fast to my satisfaction.

Their shipping can be slow and confusing, but you cannot beat their prices.

rat_stomper · Jul 18, 2019

I've never had any quality issues with RockAuto.

The resistance discrepancy is pretty minor...you're really looking for big differences like the pack is open or shorted. Since the coils are driven by a pulsed signal, DC measurements are largely invalid and the coil's inductance would be a better indicator of good vs bad...assuming you had access to an LCR meter.

If you want to go aftermarket, look into the MSD coils. I've run them on an older 4.6L and although it could have been my imagination or the original coils were weak, I swear the engine was more smooth and had better throttle response.

kustomizingkid · Jul 18, 2019

Jam them in and see if it fixes the problem... its not like they are hard to change, they sit front and center. I will second my love for Rock Auto.

rat_stomper · Jul 18, 2019

Just make sure you clean everything up real nice so they don't look like they have been installed incase you return them...most places won't take installed electronics back without a fight.

That being said they are "technically" out of spec and RockAuto would probably take them back anyway.

ewlsey · Jul 18, 2019

I'd not worry unless the resistance readings are 0 or infinite. Your numbers are pretty close to the target.

You might consider doing some basic testing. Sounds like a waste spark system. In a waste spark system the current goes through one plug, through the block, through the companion cylinder spark plug, and back to the other side of the coil. So, the coil could be shorted internally. But, a bad wire, bad plug, or any other link in the circuit can give you issues.

You can swap coil packs around and see if the missfire follows before buying a new one.

SteveF · Jul 18, 2019

Tbartoletta said:
Just make sure you clean everything up real nice so they don't look like they have been installed incase you return them...most places won't take installed electronics back without a fight.

That being said they are "technically" out of spec and RockAuto would probably take them back anyway.

That was my first concern so I emailed RockAuto customer service who called me back about 45 minutes later (damn, that was fast) and said that since I have already measured them and they are technically "defective", if I install them and they don't work I can put them back in the box and return as defective.

Thanks for the thumbs up on RockAuto from some of you. The problem with "review" web sites is the 10,000s who got good parts and everything was fine never post reveiws, it's mainly the small percentage that have a problem that find a place to post a complaint.

Think I'll install them over the weekend and see what happens.

Steve

jjxtrider · Jul 19, 2019

When several of my OEM coilpacks started misfiring on my '05 5.4l I swapped them all out with MSD coilpacks and all the misfires went away, however a year later the #5 cylinder started throwing a code in the rain and I had to put in another new one. Don't know if they're any better , the rest have been fine thus far.

.

jim rozen · Jul 19, 2019

Another diagnostic: wait for a drizzly night, pop the hood and have a buddy give the
throttle a few quick shots. Watch for the light show - wires/coil/coil pack.

SteveF · Jul 19, 2019

Yeah, learned that lesson many years ago when I wanted to twist the distributor slightly on my Mustang to adjust the timing and grabbed the top where all the wires came out. Apparently it's not just the rubber on tires that goes bad with age.

Have replaced all the plugs and wires. Just down to the coil packs to finish getting the problem with misfiring resolved.

Steve

mjk · Jul 19, 2019

I'm a big RA fan, buy most of my big ticket items, evan a gas tank, I've only had a slight bad experinace with them regarding a lost shipment, which was a Fedxxx problem. RA shipment lost policy is not user friendly

I had a misfire on a yota and although coil packs were easy to change, I swapped out plugs and wires first.
Problem went away
Some engines a misfire code can be an indication of an injector that's unhappy

ewlsey · Jul 19, 2019

mjk said:
Some engines a misfire code can be an indication of an injector that's unhappy

Miss fire codes can be caused by many things. Ignition (ECM driver circuit, coil, plug wire, plug), Fuel (ECM driver, injector, fuel pressure, etc), Compression (bad valve, worn rings, mechanical timing), etc. Other things can also cause miss fire codes, such as lean or rich condition, bad cam or crank sensor signal, faulty cam phasers, etc.

The computer just guesses at a miss fire by monitoring RPMs. I've seen them many times throw a miss fire code for say cylinder #1. After checking it out, the problem is actually on another cylinder. The ECM just gets confused. It knows there is an issue, but not exactly where it is.

Miss fire diagnoses is not always simple.

EPAIII · Jul 21, 2019

The underline on "Chilton manual" is mine. I will bet that manual does not say where those numbers come from. Ford? Did they SAY that is a FORD spec? I doubt it. Or did they just measure two or three of them? And, if they did just measure a few, how accurate is the meter that THEY used. Did they double check with another meter?

The difference is very little in electric/electronic circles. About 13K vs. 13.8K or about 6%. Common electronic parts vary by 5%, 10%, and more and still work just fine. When finer tolerances are required the designers add some kind of adjustment: I have seen a million of them. In this case I would not worry about it.

Install them and see what happens.

SteveF said:
F-150 4.6L V8, coil pack is F5LU-12029-AA.
...<snip>...

The Chilton manual says they should test at 12.8 - 13.1 Kohms between TopLeft and TopRight and between BL and BR. These test around 13.7 - 13.9.
...<snip>...

Thanks.
Steve

reggie_obe · Jul 21, 2019

ewlsey said:
Miss fire codes can be caused by many things. Ignition (ECM driver circuit, coil, plug wire, plug), Fuel (ECM driver, injector, fuel pressure, etc), Compression (bad valve, worn rings, ........

Miss fire diagnoses is not always simple.

What year Ford? Have you checked for: rainwater leak into rear plug well where hood meets he windshield cowl; coolant leak from a bad head gasket into sparkplug well?
I've had both.

crossthread · Jul 22, 2019

reggie...I just saw where you had issues with water leaking between the windshield cowl and the hood. I had the same thing happening with my F-250. I can't say really say too many bad things about the F-250 since mine has 247,000 miles on it and is still running strong. Other then launching spark plugs and drowning from the cowl it has been pretty dependable. The gasket on the cowl is a hollow rubber affair that gets squished over time and will sure enough fill the back spark plug wells with water. Not easy to get out either. Mine did it so much I started covering the front of the truck with a tarp when I knew it was going to rain. Not really a problem in normal rain but if we get a toad strangler the truck is going to run like crap until I dry out the wells. I finally took a stiff piece of nylon reinforced tubing that would just fit inside the gasket and greased it up with yellow 77. I shoved the tubing into the gasket from end to end and cut off the excess. Stopped the leak.

gustafson · Jul 22, 2019

You learn some fun stuff on this site.....

SteveF · Jul 24, 2019

I've also got the cowl leaking problem and have also resorted to covering the cab with plastic although now that I've carefully looked at it, it looks like the left and right side pieces meet in the middle and that is where the water is leaking. Am going to caulk that gap as see if that fixes it.

Unfortunately I installed the two new coil packs and it runs at about 95% with the check engine light on. Still getting a P0351 error code. Swapped in the old B side back and problem remains. Some checking on YouTube suggests a possible wiring harness problem. I live on a farm and have a rodent problem so will check to see if there might be a shorting section of wiring. Little buggers already cost me $325 when one of them ate a hole in the fuel line. Of course it was on top of the tank where I couldn't get to it. Hence the $100 flatbed bill and the $225 for my mechanic to drop the tank and replace the damaged section. Told my cats it better not happen again or it will be at least six months before they see any more treats.

Steve

ewlsey · Jul 24, 2019

A problem on the primary side of the coil should cause two cylinders to miss on a waste spark system. It will definitely not feel like 95%.

You can check the primary side with s test light. Should blink while running. Most systems are switched on the ground side.

Can your OBD 2 scanner show miss fire counters? Does the miss go away above idle?

SteveF · Jul 24, 2019

When I get up to speed it feels pretty smooth. My OBD scanner is a pretty simple one so I think I'm at the point where, if I can't find anything obvious in testing the wiring, it's time to get someone involved who actually knows how to diagnose and fix something like this.

At least it now has new plugs and wires, all installed into thoroughly cleaned spark plug tubes with a torque wrench and I even spent the time to clean out all the anti-seize from the last spark plug install in the block threads.

Steve

OT - Ford V8 coil pack problem

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