I recently had to replace an injector due to a warn O-ring. After replacing the injector the car still runs rough but not rough enough to put it into fail safe mode. I replaced the replacement and it still runs rough. All electrical connections seem intact. Any ideas? Is it possible to have a single cylinder wash down?

 

Maybe something else is wrong - start by checking fuel trims.

 

Might want to pull a compression check on that cylinder and the adjacent ones.

 

Fouled plug from the previously malfunctioning injector?

 

Is it throwing any codes?

 

Why would you assume it's only one injectors O ring? Most likely you have some others that are cracked and leaking but not enough to trip a code on their own.

You're also in the X150 forum for the newer XK's so you might find better answers in the X100 sub.

 

No, no codes but starts and runs like crap.

 

Is it running rough at idle or at speed as well? A better explaination is needed especially if no codes are thrown.

Not sure why an injector has a worn o-ring unless it is dry, cracked or damaged through service repair, if that is the case, Ranchero is probably right in pointing to other injector o-rings as a problem source too.

If the o-ring failure is the on the bottom it would induce an air leak...on the top of the injector could produce a very real fire hazard.

 

Does the cruise control work? I know, this sounds like a stupid question. Years ago I had a '97 coupe with similar problems - no cruise control and rough idle. There is a T fitting that feeds vacuum to the cruise control from the intake manifold. My T broke [old brittle plastic part] and the cruise stopped working and it idled roughly. I replaced the T and fixed both problems.

 

That's not stupid at all.

It would show up in the fuel trims (but you'd still have to find what was throwing them out).