Hello,
I have an '88 Grand Marquis 5.0L V8 with about 102,000 miles, which is having a variety of (small) performance issues that I suspect are the result of a vacuum leak somewhere. Unfortunately, these problems are intermittent, and I can never seem to reproduce them when anybody who really knows his or her way around cars is nearby. I was hoping somebody here would be able to give me their own opinion on the likely cause of these problems:
- Engine surges at low speed. When I put my foot very gently on the gas to accelerate the car from rest, the engine will accelerate normally for about two thirds of a second, hesitate for approximately the same amount of time, then surge briefly and subsequently resume normal acceleration. (If I bring the car out of rest with a greater amount of gas, this behavior cannot be discerned.)
- Occasional stumbling at highway speeds and less frequent stumbling while accelerating around 35 MPH or so.
- Air vented through the windshield defrosters. When I turn off the car after a couple miles' worth of driving on a cool day, warm air from the windshield defrosters causes the windshield to fog up on the inside, just above the vents. Could this possibly be related? The really weird thing is that the windshield never seems to fog up while I'm driving the car, but only once I've stopped it after a drive.
Any guesses at the likelihood of these three symptoms being related? Does a vacuum hose leak sound like the most logical thing to check for first? Thanks in advance!
Mark