Symptons: Engine speed will suddenly fluctuate (short burst of high revs) then settle back down. Happens at idle or coasting. The other day my wife was moving the car on the driveway, foot on brake, put it in Drive and the vehicle took off on her (as she describes it). She had to hit the brakes HARD to stop. My son says sometimes he'll be driving, take his foot of the gas and the engine will speed up on it's own, to the point where he too must hit the brakes to slow down. He stated that this happened when he was coasting to a stop sign. Any ideas? This has never happened to me while I've driven it, so I can't personally relate to the actual "feeling" of the vehicle during this episode.

I checked the vehicle over and everything seems fine (runs fine, idles fine, nothing out of the ordinary, drove it last night and nothing out of the ordinary). Other than the coolant level being WAY low (no visble leaks, but I suspect a faulty radiator cap and I will replace that today), I'm stumped.

Only other problem reported is that the brake pedal mysteriously goes to the floor, but it doesn't happen when I drive it. Brake fluid is full and all new pads (fronts and rears) within the last month.

Mileage = 105K

Your thoughts, ideas, guesses. Thanks in advance.

 

Clean the TB and IAC.

 

TB is squeeky clean. Cleaned and polished when I had the intake off 2 months ago to replace fuel pressure regulator and clean intake manifold. Will check IAC though. Air filter is new. Will clean MAF for the heck of it, too. Please keep any ideas coming. I appreciate any and all helpful hints.