My 99 SVT has re-developed a strange tendency to suddenly surge RPM when releasing the clutch while driving, escalating to about 3,750 RPM for a few seconds before slowly settling to where it should be so I can shift. During idle, the engine sits at about 500 RPM versus the normal 750. It even stalled once in traffic.
Last fall my mechanic cleaned out the manifold and MAF of deposits and grime, and it seemed to work much better. However, it's as if the clean-up never happened. I don't know if this matters, but the engine is almost at 195,000 miles.
Have any of you encountered such a problem? Any thoughts as to what this sounds like?
Thanks in advance!