1997 Jeep Wrangler Mileage and the exhaust manifold

1997 JEEP WRANGLER
85,000 MILES • 6 CYL • 4WD • MANUAL
Avatar
REDDOG7854
  • MEMBER
  • 1 POST
Recently my exhaust manifold decided to crack in 3 places. Parts are on the way to replace. Previous to the cracks my gas mileage was standard for a 4.0L Jeep but now it has dropped to 10-12mpg. Is it possible for a cracked manifold to affect the mileage that much or should I be looking for a different culprit?
Jan 11, 2009 at 9:13 PM
Advertisement
Avatar
BLUELIGHTNIN6
  • CERTIFIED EXPERT
  • 16,542 POSTS
The cracks will allow air to enter the manifold and this air will make the oxygen sensor(s) say engine is lean. Then the ECU will force very rich fuel injections. This will cause very poor gas mileage and eventually will harm the catalytic converter(s).


Thanks for using 2carpros.com!
Jan 11, 2009 at 9:33 PM