I just bought a 99 Cougar V6 with a manual transmission and it was perfectly pristine when I purchased it. I did overpay a little, but I was in desperate need of a car. I have only had it for a month, just got my plate in the mail today, and I'm starting to have some issues.

Twice now (not consecutively) I have started the car and the RPM surges and falls regardless of whether I'm pressing the accelerator or not. There seems to be very little torque and the other day when this happened and I stopped at a stop sign the RPM surged and fell repeatedly until it finally stalled. It started up again after a couple of tries and ran fine all the way home. Could this be a fuel or vacuum problem or am I looking at something more expensive and serious?

 

I had just the same problem. I too have the 1999 Cougar V6 5-speed manual. When it was happening, I had no idea what it was. The engine was revving high and idling low all by itself. I stopped at a service center to have it looked at and - just as you suggested - it was diagnosed as a vacuum leak.

They replaced the intake manifold gasket. Then they suggested I change the spark plugs while they had the engine apart and I said yes.

It cost me $430 for the manifold gasket, spark plugs and oil change.

Let me know what you find out