1989 XJS with Marelli ignition:

I've been slowly working on getting this car back together, poorly maintained and then taken apart by fools.

You've seen a few posts from me searching for solutions to running problems and I was able to solve the multiple engine issues that caused a no start condition.

However, even after it started I still thought it revved poorly and didn't run that well. I didn't investigate because car wasn't drivable. In the process of replacing front suspension and fixing rust holes in pan I removed exhaust system. Then decided to remove downpipes and gut the cats since no emissions needed where I live for this year model. (also, decided to wrap downpipes in header wrap to reduce heat).

Well look what I found, The right side catalytic converter was melted, it was nearly water-tight when I sprayed hose into it. I'm surprised car ran at all.

I'm not going to replace cats but cats might be added to a tune up procedure since they are $250 a piece on eBay.

Intact cat:



Melted cat:

 

I should clarify last sentence. I saw down pipes with cats for $260 each on eBay. Since it would be difficult to verify the condition of the cats, it might make sense for people with cars with an unknown history (future searchers on this site) to consider simply replacing cats on Marelli cars to rule out exhaust system problems.

My car started (after I fixed other stuff) and idled smooth. The only symptom was that it revved slow (I never drove the car on the street) and the right side exhaust (the melted side) was noticeably cooler than left side. I'm certain that if i'd driven the car for any distance the cat would've been glowing red.

Good luck future searchers!!

 

The melt down could have been caused by a faulty ignition amp which can shut down half the engine allowing unburned fuel to be pumped into the cats where it then ignites. Replacing the cat may not cure the problem.

 

Do you have emissions testing in Atlanta? If not, leave em out!