Hi - I have a 07 MSC just purchased which needs quite a bit of work. Several issues have been addressed so far (cosmetic / interior related), and now am starting on the engine. It has a lope to it at idle. When I log the timing and mass air flow at idle they both are all over the place. Timing fluctuated from -1 to 18 deg, Mass air flow seems to fluctuate accordingly. It had code p115c, Replaced the mass sir flow sensor and cleared the code, but the behavior remains.

If I unplug the mass air flow sensor while running, the timing settles down and fluctuates from 1-5deg. I know the car needs a timing chain (measured out of spec), and valves are badly carboned (visually checked). Question is: what would cause this behavior? I appreciate all suggestions - thx!!

 

Throttle body?
https://www.northamericanmotoring.co...115c-code.html

 

Thx Nik!! I'll try that. I also received some good advice to check if I have an internal leak through the valve cover body itself. Which, would not surprise me one bit. I'll report back what I find.

 

So I checked for leak through the valve cover, and that didn't change the idle. Then I removed the intake manifold, and searched there for any leaks. Couldn't find any. I removed the throttle body - and it had a lot of carbon on the throttle plate. I cleaned that and operated it several times. Then reinstalled everything, and...it's running MUCH better. Pretty dramatic improvement!

Thx Nik for the tip on the throttle body!

 

Glad you got the issue fixed! These cars are great fun, even with their little personality quirks.