K&N filter.
Yuck.
Get rid of that.
Put the original box and filter on it.
The original box has a temp sensor for ambient air.
That has to be hooked up.

Use
http://enginecodemaster.com
for codes

 

Thanks for the reply. I heard horror stories about people using a K&N so I removed it right away and installed a stock air filter. It does have the original box which I thoroughly cleaned. I don't see any temperature sensor. I searched but can only find an ambient air temperature sensor mentioned for the TD5 diesel engine. Is there one for the V8 engine?

 

The air temp sensor is built into the MAF

 

I have read through a significant number of misfire threads on this site and others, and it does seem that when the standard procedures fail to fix the misfires, a 'valve job' (uncertain exactly what this involves) is suggested. Maybe the shop guy suggested that as a possible problem because he knew he did shoddy work in that area??

Hope you figure it out.

 

Valve job is cleaning the heads and checking the valve guides, rockers, and springs, then seating the valves using an abrasive compound (to make sure they seal)--replacing anything out of wack.

If wikipedia says different it is lying.

If the exhaust valves "stick" they are stuck open, to my understanding, because the valve is not sitting perfectly flush with the head (because it is bent, there is goo in the way, or whatever), which bleeds off a little of your gas explosion and, I suppose, could suck exhaust gas back into the cylinder when the exhaust valve should be closed and the intake (fresh air valve) should be open.

If you remove the heads and pour water in both the intake and exhaust passages, tight heads will not leak the water. Heads with bent or "sticky" valves will leak little droplets or full blown streams. (This is a poor man's--mine--way to check the valves while the heads are off). You can also check the valves' seals by putting each cylinder at TDC (so both valves are closed), then seeing what air pressure they hold and where you hear a hiss (intake or exhaust).

Anyway, that's what I learned on youtube.

 

Some rover engines have been known to build up carbon on the valves. At some point they re-designed the valves with a "carbon cutting" design to help keep them from sticking. I'm not in anyway suggesting this is your problem.