460 efi gas mileage problem

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Mar 28, 2004 | 06:19 AM

Bill Meyer

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Joined: Mar 2004

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460 efi gas mileage problem

Just bought an '89 with a 460 EFI & 5 speed. 95,000 miles showing. It runs very strong, no apparent problems but is getting horrible gas mileage. Maybe 5. Exhaust pipe is very sooty black. No apparent leaks or other visual problems. Starts easy, idles fine, etc.
Got any suggestions as to what I should check first?
Thanks for the help.

Bill

Mar 28, 2004 | 08:54 AM

c_rossman

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Joined: Mar 2003

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From: Cloud USA

You could check the O2 sensor, ignition timing. I would check the codes also. I have a 93 with a 5speed and I get about 11-12 mpg

Mar 29, 2004 | 05:57 AM

DeenHylton

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Joined: Jan 2000

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From: Crooked River Ranch, OR

Same problem I had when I originally purchased my 1989 460.

First I changed the O2 sensor...it helped just a little but did not cure the whole problem.

Next I changed out the ACT sensor (air charge temperature) and the ECT sensor (engine coolant temperature)...problem solved! Do not confuse the ECT with your temperature gauge sensor, they are NOT the same thing.

I now average 11.5 MPG unloaded.

Deen

Mar 29, 2004 | 07:35 PM

doccamel

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Joined: Mar 2004

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One thing you may want to try AFTER you do the rest of the work, including a good old fashioned tune up is to check the fuel pressure. If it is to high or to low it will cause millage problems. Crane makes an adjustable FPR that will work fine. It is for a late 80's early 90's 5.0 Mustang but it will bolt right in and aloww you to use a guage to set the pressure were you need it. P.S. the stock pressure may not be what you need. Play with it to find the best power then stay out of the pedal.

Also if your getting anything better than 10 I wouldn't worry to bad. My crew cab gets around 7-8 in town and 9-11 highway. 14 personal best.

Last edited by doccamel; Mar 29, 2004 at 07:37 PM.