Hey everybody have been having some trouble with my 460 in my F3 50 lately been getting about 5 to 6 miles to the gallon I know In previous estimates I was getting 9 to 11 I've recently replaced the starter spark plugs spark plug wires distributor cap air box air cleaners and done a full oil change but my question is is what could be causing the idle to want to idle around 1100 RPM. I recently replace the catalytic converter and I know it was plugging up the exhaust forcing exhaust to go through the EGR valves and emissions control up in the engine compartment. Does this sound like something that could've gone bad and EGR's from having the exhaust come through or what would cause a problem like this. Any help would be greatly appreciated thanks.

 

Little more info on the truck. 1989 f350 custom 4x4 manual trans. Around 140k fuel injected. Check engine light is off. Runs all day just idles high and burning a lot more gas than normal. Exhaust stinks, not rotten egg smell more like chemical smell. Brand new cat put on 1k ago. Idled fine for first 500 miles or so now its always high. Noticeable power lose as well. Thanks

 

Sounds like the EGR is FUBARED.

 

I've got an egr on the way so hopefully that will cure the dent the fuel mileage is putting in my bank account. Keeping my fingers crossed this will be all I have to do.

 

If it's not the EGR, check for vacuum leaks. Spray something like WD40 or carb cleaner around vacuum lines and fittings, and listen for a change in the engine.

 

Check engine light off means just about nothing. There can still be lots of codes with no light. Check for codes, and do the KOEO and KOER tests.

 

Full metal did you ever figure this out? I am having a similar issue with my 89 efi 460

 

I'd start by checking the fuel pressure. It sounds like the pressure regulator is stuck. Search on here for more info on this.

 

I will have to get a gauge to test the pressure. I pulled the code and all I got was 85 which has to do the with the charcoal canister for the fuel vent.

Also where is there a port to test the fuel pressure? I looked along the rail but didn't see anything.

 

Most Fords have a Schrader valve on the fuel rail somewhere; I don't even know exactly where it is on my current truck but all of the other Fords of that vintage that I have worked on do have one.

If no test port, they do make adapter fittings that go between the fuel line and the rail (which have a test fitting on them for gauge attachment), but those adapters tend to come in the really expensive fuel pressure test sets that only the bigger shops can afford.