Purchased a 2002 lancer rally edition a few months back. 75k miles, new timing belt, automatic transmission. Recently I've noticed something odd. Fuel economy seems to have been reduced, and when in drive at a stop light, the engine gives a pulsing feeling, with the rpm bouncing between 700 and 1200 at a regular rhythm. I plan on going on long distance drives with this car and want to figure out the problem and have it fixed soon.

Any advice would be greatly appreciated!

Thanks

 

Do you have the same effect at idle? Is there Air conditioning on or off? Could be number of reasons... Throttle position sensor if exists, O2 sensor, air leaks into exhaust/inlet. I would start checking from these components.

 

During driving the air conditioning was off. The RPM only bounced while in drive or reverse. It stayed steady while in neutral.
Turning on the AC made the pulsing a bit more intense

 

spark plugs??

 

Do you have a check engine light? Could be a vacuum leak or an iac going bad.