Check STFTs and LTFTs to determine if there is a vacuum leak allowing unmetered air to enter the engine.

 

I agree. Vacuum leak somewhere.

 

 

See post 2 above.

 

I've had multiple cars give me fits w/vacuum leaks. Move, shake, squeeze, and no appreciable change. But disassemble, clean, and put on new hoses and BAM its working properly again. Often times its not just one fitting or hose. It's the sum of multiple leaks due to age of rubber parts.

A good strategy is to start at the MAF sensor and work your way down the air flow path all the way to the the intake-to-head gasket.

As mentioned above watching fuel trims live will give a good clue if vacuum leaks are happening.

 

https://www.jaguarforums.com/forum/s-type-s-type-r-supercharged-v8-x200-15/s-type-vacuum-leak-67710/

I had that rubber connector horizontally partially split. Any leak in that breather line will also cause revs to change when iddling and engine stalling.

Tip: if you cant locate the vacuum leak by sound, as I did, spray some starting pilot fluid on the intake hoses. Go over every hose meticulously. When the engine sound changes, you have found your leak. Fluid will temporarily seal the leak, untill intake has sucked it all in.

 

 

With a OBD2 scanner TPS values read something higher then 0 and never get to 100. Some readers have an option that might display it to you as 0 and 100. But the actual reading is never fully 0 or 100. You can also see V range as it moves.

Maybe a speed sensor?

 

Trims at idle should be small, not big like 10.

The TPS is high-precision so do not mess with it!!

 

Cleaning the contacts and making the ECU re-learn is a good thing in my experience. Been doing that since the 90s (don't remove it or loosen the fasteners)

 

In my FORD data logging.. a good idle when fully warm will show 0-3%. Hovering in the 0.5-1.5% area is common. 8+% seems too big with a fully warmed engine.