Hi all, took the xjr out for its test run today after replacing both head gaskets, tensioners, timing chain guides and various other water hoses etc. After start up, which in itself was a nervous moment!, it seemed to idle quite lumpy. Plugged in scanner and no faults indicated. Took it out for a drive and after 5 minutes or so it went into restricted performance mode. Plugged scanner back in and it threw 2 codes at me, one for a misfire and the other misfire/emissions too high. There is nothing more specific um afraid.

So am I missing something simple, or is there something more sinister lurking? Could the timing be out & the car run lumpy? I used the correct timing tools etc and all appeared to be fine when set and all turned over by hand after & before I fired it up.

Any help or pointers greatly appreciated.
Cheers all. Si.

Are the codes cylinder specific ? If the timing was out a whole bank would throw codes...? What codes are you getting ?

Hi, the codes are P0300 and P1316. It has done the same thing this morning too. It fires straight up, drives ok but then goes into restricted performance mode again.

I thought that if the timing was out even a little that wold be game over and a dead engine!

It's detecting a random misfire. Have you checked for obvious air leaks. Check electrical connections.

There is a definite whooshing sound coming from around the supercharger area. I have resealed the rubber gaskets between the top cover of the supercharger and the charge coolers and the charge cooler manifold gaskets have all been replaced also. The electrical connections appear to be ok, but i will take them off again and put some electrical cleaner on it all and clean them up as they have been off the car since October last year.

I had an s type r with a tiny air leak. Was very had to trace. Maybe get some Wd 40 and spray it around the joints when the car is misfiring.

I only found my fault using wds and watching the fuel mixture changing as I sprayed around the joints. Hopefully you will be a bit luckier

Theres a little more info here :

http://www.obd-codes.com/p0300

And even more in the workshop manual - free to download - and no wrong code meanings in it!