I saved my 89 XJS v12 from the scrapper a few weeks ago and just recently got it put-put-putting its way to being a running car. However, while looking under the car to make ensure nothing was on fire, I noticed that the exaust headers back to the first can (a pre-cat maybe?) were RED HOT. To me this would scream that something is plugged in the exhaust. Anyone know the ins-and outs of the exhaust that could explain to me what I'm about to cut off or suggest a good alternative?

 

Does yours have Marelli ignition? It was introduced about half way thru the '89 model year.

If so it sounds like a typical Marelli failure where half the cylinders are not firing and raw fuel is dumping into the cats and burning off.

You'll probably need two front cats but not before fixing the ignition.

Post back

Cheers
DD

 

Thanks for the quick reply! It's a Lucas and FOR SURE I'm dumping fuel into the cats because right now I'm only running consistently on maybe 10 of 12 (eh, not bad for having sat outside for 4 years). All 12 are occasionly firing. I have a new cap and wires (and plugs if I need em) that I have yet to put on. I assume I'm getting good spark because I pulled off 4 diffrent plug wires and got a good blue snap out of all of them (however I haven't pulled a plug yet). Aside from fire, what damage could result from allowing it to run and clear up?

 

Good that you have Lucas ignition although the problem we're talking about is usually associated with Marelli.

After you getall cylinders firing all the timeyou can run it and clear the cats....hopefully, with no more fuel being pumped in, they dry out and won't overheat any more. There's a possibility, though, that they've melted down and are clogged. Some guys remove them and knock out all the innards, leaving a hollow can. Illegal, of course.

Might wanna change the engine oil, too. Raw fuel may have gotten past the rings and into the oil.

When you are installing the ignition parts make sure the advance mechanism inside the distributor hasn't seized and the vacuum advance cannister still works

Cheers
DD

 

Yeah, the oil is getting done today, I can smell the fuel in it! I'm probably gonna take the exhaust down to get a look inside the cats to see if they are plugged. Thanks for the tip about the ignition, I'm still familairizing myself with this XJS. I have a 94 V12 Coupe but haven't had to do a whole lot of engine work. Electrical....thats a whole diffrent story (more like a nightmare).

 

Check the passenger side air filter. When the modulator control valve goes bad on the transmission, it will allow tranny fluid up into the intake. It then gets into a couple cylinders. It will foul out a bit. but sometimes run fine. If there is tranny fluid in a one inch circle at the air filter, that happened.

I suggest dumping one can of SEAFOAM in for eachfive gallons of gas in your tank. Run 92 or higher octane when you do this. Run that entire tank. It may pop a bit (sea foam lowers the octane and causes pre-ignition ping in some engines). The higher octane you can get the better. IT willhelp clean out the crap. I do this to my antique bikes all the time. They run like CRAP, popping and backfiring sleightly for the entire tank (which I try to empty in one long trip) and then 90% of the time run purrrrrrfectly on the very next tank with no other modifications.

So YOU are the guy that still has the cadyletic converter still installed? I heard there was someone, but was not sure the rummor was true. It is my unprofessionsl opinion, that if you dont have an O2 sensor downwind of your converter, then all it does is choke the exhaust. But what do I know. I am stupid enough to buy an XJS *wink*

David.