Try going thru these tune-up procedures might help find what making it comsumes fuel like crazy.
An engine check-up should start with a scan for any current, pending or past fault codes. This requires plugging a scan tool or code reader into the vehicle diagnostic connector so the tool can communicate with the powertrain control module (PCM).
The onboard diagnostic system does an excellent job of monitoring all the key systems, and on most 1996 and newer vehicles it can even detect engine misfires.
If no faults are found, and the engine is running normally, the check-up is not over because there are additional things that should also be checked (especially if the engine is NOT running normally or any fault codes were found with a scan tool):
Power balance or dynamic compression (to identify any mechanical problems such as leaky exhaust valves, worn rings, bad head gasket, bad cam, etc. That could adversely affect compression and engine performance)
Engine vacuum (to detect air leaks as well as exhaust restrictions)
Operation of the fuel feedback control loop (to confirm that the system goes into closed loop operation when the engine warms up)
Check exhaust emissions (this should be a must in any area that has an emissions testing program to confirm the vehicle's ability to meet the applicable clean air standards, and to detect gross fuel, ignition or emission problems that require attention)
Verify idle speed (should be checked even if computer controlled to detect possible ISC motor problems); Idle mixture (older carbureted engines only, but injector dwell can be checked on newer vehicles to confirm proper feedback fuel control)
Check ignition timing -- if possible (should be checked even if it is not adjustable to detect possible computer or sensor problems)
Operation of the EGR valve.
Checking the oxygen sensors and fuel injectors
Tuesday, February 19th, 2008 AT 3:48 AM