This is my second MINI Cooper Hardtop. My first I bought brand new, a 2012 S auto and I bought a used 2009 Justa two years later, also an auto. This issue is regarding the latter.


The Justa had a few issues when I first bought it, but the dealer took care of them save for one. Just a brief history, I took the car in right after delivery because of a rough idle upon start and it would nearly stall at times when coming to a stop. The dealer claimed that the rough cold start/idle was due to the car being given 4 extra quarts of oil while it was serviced before I took delivery. They made sure the level was correct and replaced a thermostat out of courtesy. Later that day, coolant light comes on and I had to get the car towed to the dealer. They said they put in the "wrong type of coolant" which resulted in them having to replace many parts involving cooling the engine, including a new water pump. The jerky gas pedal inputs and almost stalling issues remained so I took it back a few days later. This time, they found out that the ATF was leaking into the valve body wiring harness. Dealer resolved that issue. I took it back again because the almost stalling issue was still present. Their fix was to replace the spark plugs.


The jerky gas inputs and almost stalling issue remains, though not as harsh as when I first got the car!


Here are the symptoms:


- While in stop and go traffic or on a road with many stoplights, at about 30 or so mph, when pressing or releasing the gas pedal, the engine would respond abruptly, in a jerky manner. This only happens half the time and not nearly as harsh as when I initially took delivery of the car.


- When coming to a stop, the tach needle would dip way below 1000 rpm and almost stall, but quickly shoots back up. This happens a third of the time in varying degrees of severity.


- I've noticed that these symptoms are exaggerated when going up or down a steep grade of road. Reverse also seems to exaggerate the symptoms.


Unfortunately, since the symptoms don't frequently happen, it's hard to demonstrate to the dealer or an outside mechanic. A shop owner told me it could be the throttle actuator being gunked up or needs replacing. What's your opinion?

 

The jerky response may be worn motor mounts, the almost stalling sounds like a vacuum leak somewhere.

 

I'd say throttle body...