Mileage dropped on 5.0 Mountaineer

[kitra]

A week ago I installed the rebuilt heads on our Mountaineer (long story, see previous posts of mine). The EGR system is all new - EGR valve, DPFE, and EGR solenoid. The PCV valve and hose assembly is also new as well as all gaskets, hoses, filters, etc. Our Mountaineer has pinged since new, even with using premium fuel. Since the rebuilt heads and all the other new parts, it doesn't ping - yahoo. It runs better than it ever has. I did time the fuel injection using the Ford tool. I forget the name of the component but it goes where the 302 distributor used to be years ago. Anyway, I set engine to TDC on compression-stroke and used to Ford tool to set the injection timing. It was off quite a bit as I probably moved it 15 degrees clockwise. We are trying 89 octane fuel since it doesn't ping. But now the bad news - this tank is showing 9.2 MPG! And the trip computer has always read too high. We've never recorded such poor mileage. I feel very confident on the engine top-end assembly. I'm a perfectionist so everything was Doctor's office clean before it went back and all bolts torqued to spec (except for compensating for anti-seize by 30% or so). The only thing that was a radical change was the timing unit for the injection. Any ideas what to check to hopefully get the mileage up a bit. It normally gets 11 in town and 16 on the highway. 9+ MPG sounds horrible. BTW, the battery was disconnected the whole time I did the mechanical repairs so the ECU would have reset.

 

[rhauf]

Since it is possible you're timing is now different than it was before, i'd say advance the timing until it pings under load (or throttle), then back it off a tiny bit (so it doesn't ping).

timing can have a huge impact on mileage.

also might want to test the compression to verify that the valves in your new head are seating properly and sealing well.

 

[kitra]

Adjust the engine timing?

Is the engine timing adjustable? I only know of the timing unit for the injection and the crank sensor.