3.1 Liter very poor mileage, no engine light

[positron 12]

Hello All,


I have a 1997 Skylark, 3.1 Liter engine. I have had an intake leak, cracked rubber plug, and with such was averaging 37 mpg highway, approximately 65mph on cruise control. This condition has been for several years.

I just found and repaired the leak, a small crack on a rubber plug. Since correcting the condition, I now get only 21,5 mpg highway, 65 mph cruise control, same distance and route as before.

The engine light did not and does not come on. Nothing in "history".

The oxygen sensor has been replaced some 5 years ago.

Total mileage is 120,000 miles.

The spark plugs were replaced some 30,000 miles ago.
Spark plug wires were also replaced some 30,000 miles ago.

Any ideas of why no engine light?

Any thoughts on what could cause the poor mileage.

Thanks for time and efforts.

Pos 12

[positron 12]

Originally Posted by positron 12

Hello All,


I have a 1997 Skylark, 3.1 Liter engine. I have had an intake leak, cracked rubber plug, and with such was averaging 37 mpg highway, approximately 65mph on cruise control. This condition has been for several years.

I just found and repaired the leak, a small crack on a rubber plug. Since correcting the condition, I now get only 21,5 mpg highway, 65 mph cruise control, same distance and route as before.

The engine light did not and does not come on. Nothing in "history".

The oxygen sensor has been replaced some 5 years ago.

Total mileage is 120,000 miles.

The spark plugs were replaced some 30,000 miles ago.
Spark plug wires were also replaced some 30,000 miles ago.

Any ideas of why no engine light?

Any thoughts on what could cause the poor mileage.

Thanks for time and efforts.

Pos 12

Problem solved.