P0300 and C121C Problem - '06 XK 3.7L

[Matt]

I would definitely load the stock tune before doing anymore troubleshooting.

Normally ECU issues that result in P0300 result in an new ECU, not just programming.

Fuel supply issues could be anything from pressure bleed-off to the pump going bad. Doubtful that its an injector issue because you have a better chance of getting struck by lighting while you're on your way to collect your mega millions lottery winning than you are to have multiple injectors go bad at the same time to cause P0300.

I'm not sure what the compression numbers are off the top of my head.... but that engine would have had to been neglected for a long time for carbon buildup on the valves to do this. Again, it would have to be multiple valves at the same time to foul all those plugs.

How's your oil level?

[FLYCAV]

How's your oil level?

Oil level is good.

......... because you have a better chance of getting struck by lighting while you're on your way to collect your mega millions lottery winning than you are to have multiple injectors go bad at the same time to cause P0300.

I just wish the odds of winning the Mega Millions jackpot were more like the odds of my Jeep throwing a P0300 code on the way to pick up a 12 pack.

Normally ECU issues that result in P0300 result in an new ECU, not just programming.

I was afraid of that.

Fuel supply issues could be anything from pressure bleed-off to the pump going bad. Doubtful that its an injector issue because you have a better chance of getting struck by lighting while you're on your way to collect your mega millions lottery winning than you are to have multiple injectors go bad at the same time to cause P0300.

I just might have to invest in that service manual afterall.

[Matt]

Use this
https://dl.dropboxusercontent.com/u/...2005-WK-SM.pdf

[thance]

Use this
https://dl.dropboxusercontent.com/u/...2005-WK-SM.pdf

Do you know of a similar link for a 2010xk?

[Matt]

No, but they're practically identical except for the body and accessories.

[FLYCAV]

Thanks for the link Matt. Thats' awesome.

Replaced the PVC valve this morning and reinstalled factory tune. Still throwing the P0300 code. I guess I'm just about out of cheap solutions.

...and to kick me while I'm down, last night while online researching the issue more I got the dreaded "FBI Cybercrime/MoneyPack" virus and locked me out of my computer. was up most of the night and spent half of today getting that off my computer. (fingers are crossed)

[Matt]

Do you have a scanner that you can see which cylinders are misfiring?

I'd also check the PCM connection. Disconnect it, check the contacts, use some electrical cleaner, and reconnect.

With the engine running spray some carb cleaner around the throttle body, valve covers, etc to see if there's a vacuum leak. You'll know if there is one because the engine will rev up when it sucks in the carb cleaner.