Hey all, the engine on my 1999 Tib feels like it's 'surging' ever so slightly...up and down with revs...when the cruise control is on. As I drive an hour each day on the interstate, I think this is causing me to use up far more gas than I should be. The CE light isn't on, it's just something I can feel in my butt dyno. Any thoughts?

 

How much is ever so slightly? 10RPM? 100RPM? Does the speed change? I'm assuming you're talking about going on a straight/level road.

When's the last time you cleaned your throttle body? Does the accelerator pedal feel sticky/jerky when operated manually?

 

It's enough to be noticeable. It's not like it's snapping my head back in awe-inspiring acceleration or anything, but it's enough that I can feel it. When I think to look at it, the tach doesn't look like it's moving up and down, but half the time I'm so tired from work I wouldn't call that credible info. I haven't cleaned the TB since I've owned it, and the accelerator pedal moves freely. And yes, this is on straight roads. They occasionally have a very slight (7% at the most) gradient, and are for the most part very straight.

 

i had a very similar problem a while ago, went away when i swapped to a manual trans.

 

Check the amount of play you have for the Cruise Control throttle cable. It should be right next to the cable going to your gas pedal. Adjust the cable tension if it feels too tight or too loose. I know when I have too much slack on the cruise control cable it causes a delay after you turn on cruise control. If its too tight it creates an oversensitive feeling cruise control.

Also check for a vacuum leak.