My 140K mile 2000 S-Type 4.0 runs perfectly with the odd exception of ever-so-occasionally when it's hot it will run extremely rough on startup. Sometimes turning it off and restarting will rectify the problem, sometimes it will smooth out driving it.

No codes are being set. For the hell of it, I replaced all the coil packs with no change. I'm baffled.

Any ideas?

 

Started the car this afternoon and it felt low on power - revved it and it would not go over 3K RPM - does this sound like the 'limp home' mode I've read about?

 

Was this "not going over 3000rpm" at a stand still or not being able to accelerate past 3000rpm?
If the former, that is normal, it's a protection mode.
If it's the latter, it should have thrown a code or two, possibly with an engine light?
Do you have an OBD reader?

 

Standing still - good, it's just to prevent retards like me from grenading the thing.
I do have a code reader and no codes have been set or are pending - that's what makes this so difficult. The only thing I know is it is somehow heat related as when it happens, it's only on startup when hot - but not every time

 

Hmmm, fuel vaporising maybe with the heat...........
Just a wild stab in the dark I'm afraid, hopefully someone will come along with a better suggestion

 

When it's OK, watch fuel trims so you know what they do.

When it's not OK, watch again in the hope of clues.