Done and running...but another code has shown its ugly head just to keep me on my toes.
I replaced both upstream O2 sensors with Bosch bought from Amazone for $ 117.00 (what a difference from the original Denso sold by dealers for $ 400+!!). I drove the car for 1500 miles from PA to NC and back , averaging 25.6 mpg while cruising with a top down around 70mph. Better gas mileage than my Volvo V70. Anyway, after driving about 250 miles a "check engine" came on. Fortunately, no "restricted performance" . Code P0455. I erased it, not wanting to deal with it on the road, but after another 180 miles it came back again. It seems, it kicks in in a heavy or city traffic. Looking through forums I learned that a purge valve is the most likely culprit. But I cannot find it (1999 XK8 convertible). Where it is supposed to be mounted is only a black metal mount. I wonder whether there are some variations of the valve location, or if the previous owners modified the set-up?

 

P0455
Possible Causes

Fuel cap off
Fuel cap seal defective
EVAP system leak (canister damage, pipework damage)
EVAPP valve to ECM drive circuit open circuit, short circuit, high resistance
EVAPP valve power supply circuit open circuit
EVAPP valve to engine purge pipe damaged / blocked / leaking
EVAPP valve operating vacuum hose leak / blockage
EVAPP valve failure
Fuel tank leak

bob gauff

 

I have this list, but I thought that somebody with a similar experience can lead mi closer. A fuel cap is OK. I cannot find the valve where it should be. I did not take the wheel well plastic cover off yet - some screws solidly corroded in, so I do not want to disturb it unless it is really necessary.

 

it is necessary to get the purge valve, sorry. it could be worse...

 

more likely a CCV and vent tube though, its common.

 

what is CCV and where is it located?