Hey! Having an issue that I have been trying to chase down for a month with no success. 2010 JCW with around 88k miles.

Problem:
When stopped the engine idle is inconsistently rough. It's not always rough, and seems to be worse after the car is warmed up, but it will dip down and kick itself back up. Occasionally it will dip low enough to throw a CEL for P1497 but I think that is just consequential of the idle dropping too low and the car almost stalling. I don't believe the P1497 code any indicator of the actual problem. I noticed today that I can get the idle to do it's thing by turning the A/C on and off. When it's cut off that's when the idle drops too low. When it is turned back on, the idle raises back up. Thinking now that perhaps the car is idling too low overall and it's not an issue when the car is making itself idle higher to compensate for the A/C compressor drag. At least that's how old cars worked haha.

The following things have been done in the last 3000 miles to try and figure this out:
- Walnut blasting
- New valve cover (old one had a small leak and I was really convinced this would fix it)
- Spark Plugs

Thanks in advance for any help!

 

All signs point to a vacuum leak. Get it smoke tested if you can't find it.

 

I forgot to mention that! It has been smoke tested before with a different issue revealing a leak that was fixed prior to this issue. I THINK they did another smoke test when they found the valve cover leak but I will double check. I don't know if they stopped looking after they found one leak but I will inquire.

FWIW I have done an vacuum test at idle and the numbers were right on par, but perhaps I will re-test now with the A/C off and again with it on just to see.

Thanks!

 

PCV valve?

 

The PCV Valve is part of the valve cover isn't it? Or am I thinking of something different? If it's part of the valve cover then it has a brand new one.

 

PCV Valve is part of the valve cover. So if or when it does go bad you need to buy a whole new cover. I've had the hamburg tech one on my car for the last year and a half with no issues. I do have to say the holes for the bolts don't line up great, but theres a reason its cheaper.

 

New OEM valve cover went on last weekend. Old one did have a leak but the new one didn't fix my issue unfortunately.