Gentlemen:

Do most shops have the ability to determine which of the ignition coils is bad?

My engine light is on and I have a rough idle. Tach is steady. My mobile mechanic (a Jag guy) says it's likely an ignition coil, but he doesn't have a code reader readily available.

If attached to a reader, will the car throw a code that is cylinder specific?

Thanks all...

SirJag

 

Yes, it will. A lot of the auto parts stores will read the codes for free. You will need two things:

A cylinder number drawing as the OBDII codes do not translate directly into the Jaguar numbering scheme:

Emmission Test Failure - Jaguar Forums - Jaguar Enthusiasts Forum

. . . and an OBDII code table:

 

Once you find out which cylinder it is, I would swap the coils with the one next to it, clear the codes and see if the misfire moved to the other cylinder. If it did, you know the coil is bad. Also, the Duralast coils available at autozone for ~$100 have denso stickers on them exactly like the stock coils, plus you get the lifetime warranty.

 

Great info.. thank you!

SirJag

 

Great idea. Will do. Thank you!

SirJag

 

SirJag,

Get yourself an Infrared Thermometer. Every modern tool kit needs one and they are $30 bucks or less from Harbor Freight.

Measure the temp. on each coil. The coldest one is the bad one. I have never actually done this myself but my Manuel says it works.

BTW-- what's the BS story on a Jag mechanic with no code reader? I'm just saying----.

 

now that is interesting. If I ever get a thermometer, I will definitely try that!

 

1) Don't trust a mechanic that doesn't have a code reader... he's not proficient in troubleshooting/repair of cars built in the last 15 years. These days a code reader is as important as any other tool, not a luxury.

2) The code (that you get read at Autozone or equivalent) will tell you where the problem originates - if it's a coil, it will tell you which one.

3) Please report back when the code has been read and we'll help you from there.

 

Harbor Freight has an infrared temp gauge on sale at the moment for $7.99. It is a small one, only slightly bigger than a key fob transmitter. I have one and it works perfectly. I tested it against three other digital gauges plus an analog one at both high and low temps and it was within the range of the others which was only 1 degrees plus/minus.

The guy that dies with the most toys . . . wins!

 

Clever idea... thanks.

He's semi-retired with decades of experience with Jags, Rolls, etc. I've watched him work. He knows his stuff. Except the rough idle, I haven't needed him to diagnose any issues. He's pretty much seen it all.

SirJag

 

Thanks QM. The AutoZone idea is pure gold. It's about 2 miles away. I'll report back.

SirJag

 

This is a really clever idea. BUT... wouldn't the engine heat push the temp of the ignition coils past whatever temp they'd achieve by electrical flow alone? If so, they'd all be about the same temp. Seems to me that the engine pumps out far more heat than those coils would produce on their own.

SirJag

 

SirJag:
I have heard, but have no independent verification, that in the People's Republic of California, only certified mechanics can offfer "code reading", which, I suppose, is to prevent resetting the CEL without fixing the problem. Can you report whether AutoZone will, in fact, read the codes there?

 

Wow... what a coincidence.

I just got off the phone from Autozone and was coming here to post about what I learned when I saw YOUR post about the same thing.

Autozone confirmed. They DO NOT offer code readings any longer, thanks to another stupid state regulation (thank you, government for intruding once again).

I'll have to go to the shop. Will keep everyone posted.

SirJag