I received this dreaded evaporative emissions leak large the other day. i wanted to do know where to start. a minor misfire is noticed when the car barely has any gas applied and while idling down it misfires a minor amount. the car seems to run fine and drive fine but has a low idle and has that misfire while idling down. other than that the car seems to run great. any ideas on where to start first with these symptoms? thanks in advance joel

 

The possible causes of P0455 are:

1. fuel cap off
2. fuel cap seal defective
3. EVAP system leak (canister damage, pipework damage)
4. EVAPP valve to ECM drive circuit - open circuit, short circuit, high resistance
5. EVAPP valve power supply circuit - open circuit
6. EVAPP valve to engine purge pipe damaged / blocked / leaking
7. EVAPP valve operating vacuum hose leak / blockage
8. EVAPP valve failure
9. Fuel tank leak

Hope it turns out to be the simple fuel cap seal issue.

Graham

 

everyone hopes its a gas cap, yet rarely are we that lucky. Yes, I too had the same code. Canister Close Valve (CCV) and new vent tube needed on mine. CCV stuck open due to rust from the tube dropping into the valve. Never overfill your fuel tank when filling, it goes right down that tube that was meant for vapor!

Misfires are bad for engine/catalyst health long-term, you should also be getting a code for those; each number which will narrow it down to a cylinder or cylinders affected. Don't wait on diagnosing this, please. Its normally a bad coil-on-plug, spark plug, or water/oil in the plug well(s) from a leaking valve cover that is the most common cause.

 

I was thinkin the same thing about the gas cap issue. where is the canister located and the pipe so i can check them for rust? i haven't received a code for the misfire as it is extremely slight and can barely be heard through the exhaust but it is definitely there. it isn't causing rough idle or poor performance its just making the car idle rather low. i'm thinkin she needs a simple tune up as well. new plugs an wires and fuel filter? thanks again joel

 

Here's the Evaporative Emissions system description:

JTIS - 2001 XK8 Evaporative Emissions.pdf

This explains all the components and how they interact.

This next one details removal of the canister:

JTIS - 2001 XK8 Evaporative Emission Canister.pdf

It shows location and connections which should help you to check the pipe for rust.

Graham

 

Did you have any luck? My 1998 xk8 is reading same code. Trying to decide if I'm going to kerp this car or look for another one.

 

My new-to-me 1999 XK8 Convertible just threw this code after a long time of trying to get the Evaporative System Monitoring to reset. I have noticed a slight fuel smell from the left front of the car, and also in the trunk, so it might be multiple problems. I've ordered a replacement purge valve and a new fuel filler cap; hopefully that will fix it. Also probably going to try to replace vapor vent housing seal in the trunk. Will update with results.

 

Also spend some quality time under the car inspecting the connections and hoses to the two black rectangular plastic boxes (the evaporative canisters) between the rear wheels.