So the ongoing saga of getting this 2005 XK8 4.2 has a happy note. I’m calling it my Desert Cat Revival.

Recaps - picked up this car dirt cheap from a neighbor, didn’t run, sat outside for a couple of years, but an Arizona car so not too bad overall. Got it home and fixed all the rat chewed wires, replaced just about the entire fuel system, pump (crispy), filter, rebuilt injectors, fuel pressure and fuel temperature sensors. Had lots of codes being thrown which all cleared except crank position sensor. New sensor but car wouldn’t start, at least most of the time. Had to replace the CPS again with a better quality part and it finally came to life.

So, started driving it a bit and started getting big clouds of smoke on cold start and even after sitting for an hour or so. It kept getting worse. Then the car would start to high idle after it started moving, say around 5 mph, and when you stopped it would take 5 sec or so to idle down from about 1000 to 650ish. Kept doing test runs and the smoke was getting really bad, especially after lumbering around at part throttle, low speeds, or down long gentle slopes. When you got on it the smoke cloud was horrendous. But it would clear and full throttle runs didn’t produce any smoke. I thought the worst, failed valve stem seals, or maybe head gasket, or whatever. Along the way here I did a check below the throttle body and did see some accumulation of oil. I didn’t think it was too bad so cleaned it up and kept going.

Decided to do some in-depth investigation so pulled all the plugs and got a scope to look at the cylinders. Sure enough the piston tops were “wet”, plugs were oil fouled (new plugs a couple hundred miles ago), the intake below the throttle body was soaked with oil. Did compression and leak down test with good results, amazingly low leak down BTW, like 8%, compression within 10% across the cylinders, all pretty good for 145k miles. Yes the crankcase vent valve was oily. So, decided to disconnect and plug the line from the CVV to intake and just let the CVV vent to atmosphere, kind of like the old days before PCV systems were invented.

Oh wow, what a difference. No smoke, idle problem resolved, and it runs like a raped ape. Unbelievable really but a no brainer now that I think about all the symptoms I had. I don’t know of any way to test these valves as air freely passes through in both directions if you remove it. Yet that have a spring and diaphragm in them. So needless to say I replaced it and it the car now runs fine with no smoking.

So, if you suspect this problem on yours, just disconnect and plug the hose from the valve to the intake and see what the car does. I hope this helps someone else out there…….

 

Could be pcv sucking oil into the intake

 

Yes that was the point of my write up, bad valve sucked oil into intake. A LOT of oil.

 

Do you have annual inspections in your state? If so, will the car pass?

 

Yes we do and it passes. It’s every two years and they just plug into OBD to read codes and a visual examination of gas cap.

 

I opened the valve and can confirm diaphragm is ruptured. That was the root cause of my problem.

 

Kudo’s and thanks for sharing your experience !

max