I have a 1998 XJR, probable Nikasil victim with 130,000 miles. I know the engine has some problems - there's excessive oil blowby from cylinder #1 (the only cylinder where the spark plug is covered in oil) - I haven't had a compression test yet, but I'd guess that it's not great in this cylinder.

that nightmare aside, the car starts up fine when the engine is cold, and then runs great while the engine is warming up. A few minutes after it reaches normal operating temps (at least according to my dash guage), the car will start setting off random misfire codes and kick into limp (i.e., restricted mode) - it's very rough starting when the engine is hot (long crank), even though it fires up no problem when the engine is cold

I'm under no illusion - I need to replace the engine or sell it 'as is' in the not too distant future - but I still would like to figure out why it random misfires, and starts rough when the engine is hot. Any ideas would be appreciated.

 

any codes.. if there egr is full of carbon.. can cause some problems as well.. i sent you a quote .. earlier.

 

the only codes are the P0300 (random misfire) , and the 'misfire above limit' code. EGR was full of carbon - I cleaned it out, but it still may not be working properly - I plan to replace it to see if that helps. Something didn't seem quite right with the spring/valve part -- I think if anything, it's stuck closed.

It's running lean, if a new EGR doesn't help, it may be injectors? fuel pump? The injectors in the 98 xjR are a pain - it looks life the supercharger needs to be removed to get to most of them. Hopefully a new EGR will do it.