My engine seems to have a miss. I trying to test the coils and get a primary reading of 0.5 on all 8 coils and secondary readings ranging between 5680 and 6150 ohms. Is this within specs, are the coils ok? Thanks!

 

I guess as they cool down, the readings change. Secondary now reads between 5390 anf 5630. Any Ideas?

 

Primary resistance should be .55 ohms.
Secondary resistands should be 5500 ohms.

I would say your coils are ok...

 

At what point are they bad?

 

I do not know what the tolerance is for the cop's. I would also say it is normal for the resistance to increase as the temperature increases.

Is your truck giving you a diagnostic code where it is always missing on one particular cylinder.

Do you get diagnostic codes showing misses on several cylinders?

 

That's the whole frustration, there is no SES light and no codes, but the truck is misfiring and doesn't accelerate as well as before! There's a slight shudder also.

 

Do you have 4.6L engine?

How many miles on your truck?

When did you last change the fuel filter?

 

No it's the 5.4, only 38k miles. I've already changed trans oil, fuel filter, spark plugs and cleaned IAC and throttle body but still have the problem!!

 

Wow! Does it miss only at idle? Mine misses once in a while when it idles. I have been meaning to check my TPS setting.

 

Not only at idle, it doesn't accelerate strong. The TPS was my next thing, but I'm trying to work thru the coil issue first.

 

I used to have a Maxima and the fuel pump went squirrley. The car seemed to run ok but It did not have good acceleration. It accelerated poorly at times and fair at other times. It changed each time I started the car. I could hear a faint whine from the rear of the car where the fuel pump was in the gas tank. The fuel pump was replaced and it ran like a scalded dog.

I personally would check fuel pressure or clogged injectors if you run out of idea's. Sounds like you have a bitch of troubleshooting session in progress.

Good Luck!

p.s. Be sure to post back the solution if you find one...

 

I've heard of getting misfiring but no CEL.

So you could try scanning for codes just in case it is throwing codes but not the light.

 

I'll look into the fuel issue.

I have tried scanning it to see if there were any codes, nothing, "PASSED, NO CODES READ"!!!

 

I had the same problem with my 02 5.4 ---drove me crazy for about 8K miles (and 4 trips to the dealership). Turned out the #3 and #4 COPS had gotten wet (I guess by A/C condensate). The trouble with our diagnostic system is that it won't throw a light if there is an "intermittent" problem with the COP. However, that same miss will retard the timing and make the truck run like crap. I found my problem myself when after the truck's 4th visit to the dealership (it had stayed there for 5 days), I decided to put a set of plugs in it myself---it couldn't hurt.

I replaced the plugs and moved the #3 and #4 COPs up to the #1 and #2 position (so I could get to them easier). I did have to replace the one that had been on #4 and as long as I keep some dielectric grease on the one that had been #3, it does fine.

NAPA has the coils for our engine--even though their books do not yet show it. Ford changed the coil, I believe, in 2000 as a "running change" The NAPA # for the COPs for my truck is IC-369. It took some doing, but I found the number.

If you power-break your truck and it misses at about 1500, I would be willing to bet that you have a bad COP.

Sorry to be so long winded,

Sidewinder

 

Sidewinder,
Thanks for the input! It is driving me crazy. it's been like this for around a month and I've gone through so many things and feel that it is a coil problem also. I've inspected all the coils when I was changing my plugs and visually I didn't spot anything such as condensation or anything and so did the resistance test and got the readings I posted above. I'm running out of things to check and getting damn frustrated!!!!!