I noticed awhile ago that while I am driving at a constant speed, my RPM gauge would rev up and go back down to normal over and over again. It did this for about a month or longer so I talked to my mechanic. He said that it was probably bad fuel. I started putting Marathon's premium fuel in it, which coincidentally is when the RPM's started shooting up. So I took my car to a Casey's General Store and put normal unleaded in it. It runs a lot better since I started doing that, but I noticed that every once in awhile the RPM gauge will shoot up like it used to, but this time, when it shoots up, it takes longer for it to get back to normal RPMs. I'm wondering if my problem is still fuel related and if I should replace the fuel filter and fill the gas tank up with a can of seafoam to help clean it up. If someone knows more about this any advice would be appreciated!

 

A new fuel filter is a good Idea between 20 and 50K, some Lucas Oil fuel additive should clean up your injectors as well. Any idea when the fuel filter was changed last?

 

I bought the car over three years ago with 96k on it. It now has 117k and as far as I know it has never been changed. I know I've never changed it.

 

When the rpms surge up does it feel like the car slows down or like a downshift or there is resistance going forward?

 

I'm not really sure. It doesn't feel like it's slowing down. It doesn't do it very often so I don't have much experience with it

 

I'd check for vacuum leaks first.
Assuming it has not been done, at that mileage consider changing plugs and wires as well (even if it's not part of the problem, it's good maintenance). OR, if the plugs were replaced with BOSCH, rip them out (I've had too many weird BOSCH plug related issues.
And I echo the same comments about the fuel filter.

You may want to check this for other maintenance ideas that could relate to your issue:
https://montecarloforum.com/forum/fw...0-miles-46078/

 

I changed the plugs and wires at around 100,000 miles. I used NGK brand plugs. I'm planning putting a new fuel filter on today along with an oil change so we'll see how that goes. I'm probably going to try some Seafoam or some other kind of injector cleaner to see what that does