I have an '89 E-350 with FI 460. The engine was recently replaced with stock remanufactured but compared to the old engine (which had some badly burned valves) power is significantly less and gas mileage dropped from an average of 12mpg to only 6mpg highway with the same driver and general (easy) driving conditions.


It starts and runs okay but I'm suspecting the cam is retarded. I put a manifold vacuum gauge on it and with idle ignition timing at 30deg. the idle vacuum sits at 16" Hg. Anyone with 460 experience care to speculate?

 

EFI engines run straight up cam timing.

I don't think anyone sells a retarded timing set for '88 and up.

What is your ignition timing set to with the SPOut plug removed?

 

As far as I know the timing sets are interchangeable and they could have also got it off a tooth.

Base ignition timing without SPOUT is 12deg. Retarded ignition timing can contribute to lower vacuum but that is not the case here. It runs at stock 30deg. at idle with SPOUT. 16" Hg seems lower than it should be but I thought I'd check with others.

 

16" does seem kind of low.

Certainly your mileage and power loss are coming from somewhere.
Are there any stored codes?

How many miles on the rebuild?

 

There are presently no codes, but when I first got it back it generated two codes, one for the evaporative canister solenoid and another for lean. I fixed the solenoid issue (connector was broken and disconnected) and the lean code stopped occurring.

There's about 2k on the rebuild.