If anyone has any idea what else could be wrong with my truck please reply!!

I've got a 97 f150 thats getting 10-12 MPG on the highway and I think it should get 17-20. About a week ago I found that the control valve for the vapor canister was plugged up with dust, so I cleaned it and the canister out with air. It set off code 1451 the next day.

Here's what else I've tried.

Gutted both cats and Put a used one further back (also moved O2 sensors)
New Plugs
New Wires
Replaced 2 O2 sensors (No more O2 Codes)
Replaced Air Filter
DPFE Sensor
Cleaned Bypass valve on Vapor Canister
Replaced Fuel Cap
Cleaned EGR port
Cleaned VCV for EGR valve.

Also when I extended the O2 wiring harness further back in the exhaust I used solid core wire, and someone told me this might be a problem.

Thanks A Lot!!



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You cannot move the Ox sensors back farther away from the engine.
They must operate at 650 degrees or higher to work.
The heating feature is only to help get them up to operating temerature faster.
If they do not provide the computer with a "controlling" signal that controls fuel injection levels, the computor will go to open loop operation and very rich fueling results.
There goes your fuel milage.

 

Thanks for the help. I guess I'll just have to replace the factory cats and move the O2 sensors back to their original spot. I'll keep ya'll updated.