1991 xjs v12 Occasionally the left bank ( Nearside ) will missfire, backfire and exhausts will get red hot mostly at low speeds but will kick down and accelerate okay but on slowing down will missfire etc again. Sometimes the check engine warning will light but not always. My local garage who is a jag enthusiest has done all checks but no result. Any ideas?
Norm.

 

Welcome to the forum Norm,

You've found the right place for advice on the misfire.

When you get a minute, please follow this link New Member Area - Intro a MUST - Jaguar Forums - Jaguar Enthusiasts Forum to the New Member Area - Intro a MUST section and post some info about yourself and your vehicle for all members to see. In return you'll get a proper welcome and some useful advice about posting to the forum.

Graham

 

You have Marelli ignition which means each half of the engine runs on a separate system, so it is very easy to lose half the engine if one of the components fails (ignition amplifier, coil, something in the distributor)

Do I understand it right it is an intermittent issue ? ie sometimes the car runs fine, but then sometimes it misfires on one bank ? Does it only do it when the car is hot ?

Does the car have catalytic convertors ?

Your exhaust is glowing red because you are dumping unburned fuel into it, which is igniting. This is not good.

I understand your mechanic saying all is ok if the issue is intermittent, and the car is probably behaving when he looks at it. Did he take the car out for a run?

 

Exhaust getting red hot and back firing is usual retarded ignition timing.

 

From what I understand these symptoms are classic Marrelli failures. I would check that system 1st.

 

My thanks to Oddrods, Icsamerica and Sarc for your replies and advice. To answer Sarc's questions; intermittent, yes; hot, yes; catalytic converters, yes and my mechanic has tried runs and static idling. The first time problem occured was about 18 months ago then about 1 month ago then just last week. The check engine warning often lights for the four years I have owned it and also the previous owner, ( A good mate so I knew about it ) Just stop the car, turn off and restart the ignition and warning light is off. My mechanic has done diagnostic checks but I don't know if that covers the Marrelli issue. I will pass on the Marrelli tip to my garage and post their reply.
Thanks again,
Norm.

 

Check connections to the O2 sensor on the hiccuping bank. Also the rotor and of course go to the XJS book on checking / fixing the rotor issue for Marelli 12s, ref comment above. As it has been going on for a while also check condition of the dizzy cap for tracking. And do it now! Else the car might catch fire.

 

Thank you Per. Will do.
Norm.