2002 Chevy S-10 Poor Gas Mileage

SPRINTERMAN52

MEMBER
2002 CHEVROLET S-10
4 CYL
2WD
MANUAL
103,000 MILES

My truck used to get 22 around the city and up to 28 on the highway. Now I am barley able to keep it at 21 on the highway. Put new spark plugs in, wires were fine and still getting no better than 21 mgp highway. All fluids are at good levels, tire pressures are all good. The only other problem with the truck is that a bearing is worn out in one of the engine pulley's. But would that cause the poor mileage? Why is my gas mileage so poor?

1 Reply

CARADIODOC

MECHANIC
33,873 POSTS

A bearing could cause lower fuel mileage only if it is making a vibration that is picked up by a knock sensor. I don't know if your truck has one, but GM typically needs them to prevent spark knock. When those vibrations are sensed, the Engine Computer momentarily retards spark timing. That reduces power and fuel economy.

You might also look into dragging brakes. Park on a slight incline, push in the clutch, and release the brake. The truck should roll downhill on its own. If it doesn't, we should talk about some things to check.

A leak in the exhaust system can kill fuel mileage, but typically only by about 10 percent. These things can be found by watching sensor values with a hand-held computer, called a scanner, while driving the truck on the highway. Reading long and short-term fuel trim numbers will provide some clues too.

Caradiodoc