I have a 1998 Bonneville SE which has the 3.8L V6 engine. With the car at idle or any gear the tach nettle starts to go up and down slowly then it moves faster from near stall to 2000 RPM. After doing this for about 25 seconds it stalls. I think it is the EGR valve staying open. It runs fine with more gas but I can smell fumes. The car has 133,546 miles on it.
I haven't done anything yet. I am having a person checking it out. Nothing is showing up on this computer. No check engine light. Someone else did say it could be a vacuum leak or the EGR valve.
I will have my friend clean the MAF,