My engine missfires at between 1600 and 1800 rpm regardless what gear it is in. So far mechanics have not been able to find the source of the problem.

The truck is a 1989 F-150, 6 cylinder, fuel injected with 93,000 miles. Lariat with dual tanks, fore and aft.

I am wondering if the problem could be with the fuel pumps? If anyone has had similar problems, please let me know what it took to fix this.

Thanks very much for your input.

 

Try unhooking the vacuum hose at the egr valve and drive it. See if problem is now gone. Even if it is I won't be able to tell you wat to do to fix it. My 89 300 6cyl has done this for years. I work on these daily. Have replaced egr valve, egr solenoid, evp sensor, flushed injectors, and have learned to live with it.

 

Don't know if this will help but it doesn't cost much. Some times at a certain rpm and fuel flow, the ability to burn the fuel will decrease to the point that the plug wire can miss fire to the block. Try putting some dielectric (plug boot grease) inside the plug boot then putting them back on. Coat them well but keep it off the contacts. A very inexpensive fix and from what I remember of that engine, easy to do...

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Black 1997 F-150 Supercab Flairside. 4.6L with Superchip, Jacobs DIS, K&N Generation II, Cat back Exhaust with Flowmaster 40 and MEG'S Stainless tip in front of rear wheel (nice rumble). 17" Off Road wheel pkg. Lots of body mods. 5 yrs old and still turns heads...and now paid for!! New is NITTO NT404 275/65/17's and Hellwig 1/7/16 front and 1 1/8 rear bar.

[This message has been edited by WLF (edited 04-02-2001).]