I have a 1998 XJ8 that was running rough when purchased and the timing chain clack was very audible. I changed the tensioners on both sides and car still runs extremely rough. I can pull the spark plug wires on the driver side and engine gets worst. However, I can pull any spark plug wire on the passenger side and the there is little to no change in the engine idle. My thoughts are that the right side (passenger side) camshaft chain skipped a tooth on one or both of the cams prior to my changing the tensioners and I put it back in the exact wrong spot. Is there anyway to determine if one or both of the cams are out of time or how to accurately reset?

 

put the crank lock tool in the oval hole on the flex plate, it's 40 deg after tdc

move all the cams till the flats point up then put the chain back on

 

I guess part two of the question was answered, but first rotate the engine round by hand until all the camshaft flats line up. If one cam has skipped a tooth, it should be pretty obvious. Maybe get one bank to line up but the other side then has one or both cams out of phase. Sounds like you bought it with an undiagnosed problem and the previous owner may have continued to try to drive the car for a long time after the first sign of tensioner failure. If my logic is correct, its the exhaust cam you have to worry about piston strike because if it skips, that means the exhaust valve stays open later while the piston is approaching the top of the exhaust stroke. Don't know if one tooth will make it hit or two. An old shade-tree mechanic test is to hold a dollar bill up to the exhaust pipe (you can find videos on youtube) and if its being blown like a fan, then its fine but if it seems to be getting sucked back into the exhaust, fluttering in and out, then you have something wrong with the exhaust valves (either timing, damaged seats, bent stems, etc). Its at least an easy check that anyone can do. HTH.

 

Thanks Phil. I'll give it a shot when I'm off the week after Thanksgiving and let you know how it goes!