Was going over my injectors and coils yesterday, checking connections etc.. when I noticed that when I unplugged the front passenger side coil (not sure what cylinder number and I don't think it matters), there was no change in the idle. Same happened when I unplugged the injector. All other coils and injectors changed the idle when unplugged. I also noticed when I removed the coil from all other plugs while the engine was running I could hear the coil spark jumping before I got the coil out, but this was not the case on the one on the passenger side. Tried a simple test of putting a test light inside the coil boot and was barely getting any spark, the others were jumping out of the boot. I replaced the coil and still no change.

Any suggestions?

 

Is the connector making connection to the coil?

 

That would be #1 cylinder. It should be labeled.
you might need a new pig tail or the wire is shorting out somewhere.

 

It is clipped on, so that seems fine. I'm wondering if there is a way to check the connector itself?

 

Are you talking about the entire coil pig tail?

Also it idles fine, except for the occasional miss, but when I accelerate it misses bad. It will eventually smooth out but it gets rough (jerky rough) around 45 to 55 mph.

I am thinking it has to be either a fuel or spark problem. What else is there?

Maybe the pig tail connector is shot?

 

I would get a voltmeter and tap the metal pins inside and see what you get. Compare it to a good connector and see the difference.

You may have a ground issue?

 

One other thing I thought of, is the spring inside the boot corroded? Are you getting good contact with the coil?

If that is ok, then I would check/replace the spark plug.

If you're due to have the plugs changed, I would bite the bullet and have that done and replace all the boots as well.

 

I will pull the plug and check it, but I changed them out when I got the truck 40,000 miles ago, and I used Bosch so they should still be good.

I put a new coil on the #1 plug and the low spark is even in the new coil, so I am thinking it has to be a harness/wire problem. Not sure how one wire might lose power but it seems that's the case.

 

OK, let's think about this a minute. You have a 12 volt signal fired to each of the 10 coils at the proper time. In order for you to have a "low spark" condition, you either have a whole bunch of weak COPS, you do not have a 12 volt signal firing the COPs, or you have a bad ground on the engine itself.

Why do you think you have weak spark?

Oh, and yes, the Bosch plugs can go bad at 40,000 miles. These modular engines seem to really likes Motorcraft platinum plugs.

 

"or you have a bad ground on the engine itself."
Ok, so this should be an easy fix. Just get a ground cable and ground the engine, right?

you do not have a 12 volt signal firing the COPs
Is this possible and is there a fix? One member suggested the pig tail might be bad.

"Why do you think you have weak spark?"
On the #1 cylinder, I removed the connector to the coil and the engine idle did not change. I also removed the connector to the injector. (while coil was connected) on that same cylinder and no change. The idle did change on all other plugs and injectors when I did the same thing.

As well I pulled the coil out of the #1 plug while the engine was running and was not getting any spark jump, but in the others that I did this to I did. I put a simple test light into the boot of the coil and wasn't getting any spark jump like I did with the others.


"Oh, and yes, the Bosch plugs can go bad at 40,000 miles. These modular engines seem to really likes Motorcraft platinum plugs."
Thanks, I will remember this next time I do a change, which might be soon.

 

Bad COP would be my first guess. Swap it with another cylinder, see if the problem follows the COP.

 

I will do that, but I just put a new one on it. Thought it was bad. I am going to check my plugs too. The truck idles fine with some rough spots now and again. It really runs rough on acceleration.

 

I am going through a similar issue with a misfire. Even though your engine light is not on, you should still have a misfire code (P0301-P0310). It may be worth the effort to go to a local auto parts store to see if you can barrow their ODB scanner and check.

 

I have a 2000 F-550 with a V-10 and 70,000 miles. This fall it started running poorly. Idled fine but had no power. No CEL. Replaced all sparkplugs with Motorcraft and all coils with aftermarket from Amazon. Runs great now! The difference was amazing! I inspected all of the original coils and many of them had hairline cracks on the top.

 

You may want to pull the plug and have a look at it. Weak spark and misfires will make the plug look black, with carbon deposits.

I would guess that you'll see the opposite, the plug will be white. It should be light brown. White would indicate a lean mixture, which is probably caused by a vacuum leak.

Spark Plugs