How to spot a bad coil?

[Ict_Lx]

I have recently developed an engine stumble while at idle on my 97'. It has progressed to a loss of power until right after 2000 RPM's. The engine feels like it is really bogging down and then it takes off. At first I thought that I got a bad tank of gas so I waited until I needed to fill up again and replaced the fuel filter and put a gas additive in. Needless to say the problem is getting worse. I scanned the computer and no codes were present. The guy at Advance tried to tell me that if there was no code then the coils couldn't be a problem. He also said that I would get a code for spark plugs being messed up....The plugs are almost new. They were replaced at 37,000 miles when the cams were welded (49,300 right now). Any help would be appreciated. Thanks.

 

[Ian Macoomb]

I haven't been able to determine any difference between a bad coil and a good coil. You can't look at it and an ohmmeter doesn't always work either. The only good way to find a bad coil is to get the Ford stealer to run a power balance test on their WDS (Worldwide Diagnostic System). Or you can wait till it gets real bad and sets the check engine light. I've found that I can sometimes get a pending code by throwing the shifter in 2nd and hammering the gas from a stop. The engine will bog and you get your pending code if you've got a code reader hooked up.

 

[Ict_Lx]

That's not good. I don't have a code reader so that wouldn't work very well. I would just start guessing and changing coils but that would get pretty expensive pretty quick. With my luck it's going to be one on the rear bank too. Does this even sound like a coil going out or am I looking at the wrong thing as the potential problem?

 

[Ian Macoomb]

Definitely sounds like a coil to me. They tend to go bad after being handled like during a cam weld or a plug change.

Might as well replace the rear 4 all at the same time so you don't have to do the job more than once. Murray's has got the coils for ~$60.

And while you're at it you might as well get a code reader. Consider it an investment. Every Ford owner should have one.

http://www.harborfreight.com/cpi/ctaf/displayitem.taf?Itemnumber=46030
http://www.autobarn.net/eqobdiicodre.html
http://www.midwayautosupply.com/detailedproductdescription.asp?3352
http://www.actron.com/whats_new_detail.php?id=20

 

[Ict_Lx]

Thanks Ian. I'll probably get the one from Harbor Freight on Monday. Where do you get the Murray Brand Coils from? I checked Rock Auto and they had a couple different brands, all for more than $60. The motorcraft part was $100.99 for one! That's a little rediculous. I guess it is a SHO. I don't know why that surprised me so much. Thanks again.

 

[Ian Macoomb]

Ask and ye shall receive:
http://v8sho.com/SHO/MurraysOnLineSourceofReplacementCOP.htm
http://v8sho.com/SHO/SurgeTank.htm
http://v8sho.com/SHO/BestSourceforQualityCoils.htm

I could go on but you get the point.

 

[SHO_of_SD]

MAF getting dirty??

 

[Ict_Lx]

MAF getting dirty??

I guess that's something easy to check out. I hadn't thought about that either.


Thanks Ian.

 

[KILLA]

I this exact same problem not 3 weeks ago. My check engine light didnt come on until it was missing 90% of the time.
It could be a coil. The WDS will be the easiest way to check.
Cross your fingers its not in the back 4 cylinders.

 

[nik97]

Yea, power balance will be a good way to reveal a missing cyl. However, if a WDS is not available and there is a suspect coil, pull injecors one by one at idle and feel/watch for the one that causes no change.

 

[Ict_Lx]

Yea, power balance will be a good way to reveal a missing cyl. However, if a WDS is not available and there is a suspect coil, pull injecors one by one at idle and feel/watch for the one that causes no change.

Can you reach all of the injectors pretty easily? I have pretty big hands so some things that a normal person can reach doesn't work out so well for me. What is WDS? Some sort of Diagnositic system i'm guessing.


Nik97: Is that picture of your car in your sig photoshopped? I could have sworn your car was red. Looks badass though. I really like the all black look. Headed that way myself one of these days.

 

[greg geraci]

Can we tell by the color of the spark wether it's blue or yellowish ?

 

[nik97]

Can you reach all of the injectors pretty easily? I have pretty big hands so some things that a normal person can reach doesn't work out so well for me. What is WDS? Some sort of Diagnositic system i'm guessing.


Nik97: Is that picture of your car in your sig photoshopped? I could have sworn your car was red. Looks badass though. I really like the all black look. Headed that way myself one of these days.

Yea, my car is toreador read. No photoshop, just messed around with the red eye reduction while in iphoto. I wish it was jet black like that tho...someday.
Some of the injectors are a little tricky to get at. Get one finger in on one side of the clip and a flathead on the other and gently pry up.
Oh, WDS, the windows '98 based diagnostic system used in Ford dealerships. Replaced previous NGS and is soon to be replaced by laptop PC compatable software(much faster date rate than Windows'98). :type:

 

[nik97]

Can we tell by the color of the spark wether it's blue or yellowish ?

If you haven't already, pull your'e apperance cover and check the front coils first. Run at idle and disconnect coil terminals one by one. If this doesn't spot a bad coil, start diconnecting injectors.

 

[Ict_Lx]

Yea, my car is toreador read. No photoshop, just messed around with the red eye reduction while in iphoto. I wish it was jet black like that tho...someday.
Some of the injectors are a little tricky to get at. Get one finger in on one side of the clip and a flathead on the other and gently pry up.
Oh, WDS, the windows '98 based diagnostic system used in Ford dealerships. Replaced previous NGS and is soon to be replaced by laptop PC compatable software(much faster date rate than Windows'98). :type:

Thanks. I pulled the four injectors I could reach without tearing into anything when I got home this afternoon. All four of them made the misfire worse. I'm guessing that means it's one of the back 4...

 

[nik97]

Thanks. I pulled the four injectors I could reach without tearing into anything when I got home this afternoon. All four of them made the misfire worse. I'm guessing that means it's one of the back 4...

You pulled the the four injectors or the front 4 coils? If you pulled the front coil terminals individually and the misfire got worse, then yeah, it may be one of the rear ones. If at all possible, try to undo each injector one by one or at least the right bank(rear). At least by doing this you can determine if an actual misfire is present before removing the manifold. If so and you do remove the manifold to replace one, be very carefull when handling them as they are extremely shock sensitive. I found this out the hard way and had to dive right back into it as soon as I thought I was done :cry:

 

[crixtopher]

Yea, my car is toreador read. No photoshop, just messed around with the red eye reduction while in iphoto. I wish it was jet black like that tho...someday.

that answers one of my questions

the other is, are those stock wheels powdercoated black with cap removed and blue tread rubber ?

nik, thats one sweet a&% ride

 

[Mr Anonymous]

Thanks. I pulled the four injectors I could reach without tearing into anything when I got home this afternoon. All four of them made the misfire worse. I'm guessing that means it's one of the back 4...

You have to listen very carefully for the misfire cadence.

Since most misfires from weak coils are intermittent, after you disconnect each coil/injector, you need to listen for a bit to see if you can still hear the intermittent miss underneath the steady miss you have just induced. When you can no longer hear the skipping in the background, then you have identified the cylinder in question.

 

[crixtopher]

You have to listen very carefully for the misfire cadence.

Since most misfires from weak coils are intermittent, after you disconnect each coil/injector, you need to listen for a bit to see if you can still hear the intermittent miss underneath the steady miss you have just induced. When you can no longer hear the skipping in the background, then you have identified the cylinder in question.

Dear Mr No Picture, not trying to hijack the thread but didn't you and others mention a "ghost misfire" condition that happened relating to the X-Cal ? can't remember the details now.
Before I got my tuner I had zero problems , but a few weeks after installing it I noticed a slight miss at idle which seems to be getting worse. but it seems* to go away once its nice n warm. wondering is this is what you were talking about before and if so anything I can do ? I don't wanna just start swapping coils, though its not quite bad enough yet to do anything. I also developed an SES that I need to go have read since my moronic **** doesn't have a code reader : )

 

[SHOZ123]

With my Xcal2 tuner and the Advantage software I richened up the mixture. On the cold fuel and spark tables I went back to stock. Took most of the miss a way.

Try disconnecting the battery to see if the miss gets better.