Hello All,

I have a 2004 XJ8 that I LOVE. 111K Changed plugs at 95K. I have had a rough cold idle for several months, but it never threw a code (or at least no Check Engine light, and no restricted performance). Well now that it is getting cold I have 8 codes.
P0171
P0174
P0300
P0302
P0304
P0307
P1316

Can it be that many bad coil packs? Is there any other known cause?
I also replaced the Throttle body at 95k.

Any advice on where to start would be great! Thanks in advance.

Vince

 

Geez! I put this under the wrong forum, but I don't know how to move it.....Help?

 

You have an air leak, very likely the big tube from the filter to the throttle body. Remove it and check for cracks, particularly on the on the underside. If you find some tape them and check again. It's unlikely you have coil failure to that extent, it may be a function of the lean mixture.
If you get rid of the lean codes and still have the coil codes, try switching them and see if the codes follow the coils.

 

Hey RJ,

I am not near the car, so I can't check right now, but I do remember that the nib (?) that mounts the pressure tank, attached to the hose is broken off. I wonder if there is a crack in the tank. Thanks for the info. I will report back.

 

Thanks for the tip RJ! I pulled off the intake cover, and low and behold, the hose end at the throttle body was not secured properly! I reattached it, and the rough idle at cold start was all but gone. I let the car warm for a couple of minutes, and headed out into the snow. The car ran fine, but it did idle rough at a stop sign about half a mile from my house. Does the computer have to reset or something? I went to my friendly neighborhood Jag guy, and he cleared the codes for me. I will see if it throws any more codes to the reader on Friday. The check engine light does not come on the first time there is a misfire, does it?