1998
Pontiac Grand Prix SE
3800
162k

Its been a couple months since succesfully replacing the intake manifold on my grand prix. Car ran like new for about 3 weeks. Then one day it began to idle rough and accelerate rather rough, to the point it vibrates all the plastic components on the dash to an irritating rattle. Gas consumption also seems to have increased rather significantly. After popping the hood with engine running, I noticed a rather large vacuum leak. It was coming from the MAP sensor. I took out the sensor and noticed the orange seal was damaged (most likely due to taking it off/on when replacing the manifold) I put some ATV silicone blue around the seal and it stopped the vacuum leak, but did not fix the performance issue with the rough vibrating idle and accel. I checked out some symptoms of defective MAP sensors, and some of what the car is doing, seems to relate to that. Anyone have any suggestions before I spend $40 - $60 dollars on a sensor that may not even be the problem?

The MAP sensor controls fuel mixture. Long periods of driving it with an over rich mixture will would the spark plugs and cause a misfire. I suspect your well past that point. Remove the spark plugs and if any are fouled, I would replace them all.




78 Corvette Pace Car For Sale-18k mi orig-Florida