Went for a drive yesterday. Two minutes into it, this noise (listen to attachment) began and rapidly increased in volume. Just a regular drive, no full throttle or anything else. The $100 bill test shows that a cylinder is not firing on the right bank. The noise is tied to throttle setting, the more I throttle, the faster the noise. No maintenance has been done recently, this just came out of "nowhere". At the same time, the engine will drop from around 900 RPM to a few hundred, and will then surge back to 900. It does this in just a second or two.

Started it up today and the noise immediately appeared.

Thoughts?

Thanks in advance,

John
1987 XJ-S 5.3L V12
Around 75,000 miles.

 

Sounds like a really bad exhaust manifold leak at the head, or maybe a sparkplug backed out. Shouldn't be hard to find. An automotive stethoscope might help to pinpoint the leak.

 

I heard that once, a spark plug was backing its way out.
(';')

 

Good call gentlemen! Seem the rear sparkplug on the right bank lots its top. Of course it couldn't have been one of the easy-to-reach front plugs :-)

The fluid around it isn't oil, it's PB Blaster. Plug is stuck so I'll give it some time and replace it.

Thanks,

John
1987 XJ-S V12

 

If the number six plugs are that bad, how bad are the number one plugs under the AC compressor? Those are the ones that usually get skipped. Might be time for new plugs all around! Don't forget to gap them to 0.025", it matters.

 

Probably not a bad idea. I don't have a problem with the plugs under the compressor, as I took the compressor out (along with the cruse control hardware) a long time ago. Actually, I bought a Sanden compressor and hung it where the air pump use to be, so top work isn't as challenging in my case as in most.

Thanks!

John
1987 XK-S V12