I bought a 1995 F150 5.8 4wd about 2,000 miles ago. It was getting pretty good mileage when it suddenly dropped to about 10 mpg. And starting became somewhat erratic with rich exhaust.

I immediately thought O2 sensor, ordered a new one, and installed it, but no change in performance.

My question is, what could affect the mpg that drastically? I read the PCV valve can cause some, but that much?

The idle is fairly smooth except it seems to hunt up and down a little. Sort of like an engine that might be a little rich and leaned out a little, then back again. Or vice versa. Dunno if that could be related or a separate issue.

If it had a carb and a distributor, I'd know what to look for. As it is I don't have a clue with out taking it to someone with a hook up.

Thanks, Harold

 

Need to hook up a scanner and look at sensor values to be sure what the problem could be. Before that I would check for vacuum leaks with some carb spray.
.

 

Thanks, i'll work on the vacuum. Be a few day before I can go to town. I'm even out of WD40. I'll report back what I eventually find.

 

Turn in your man card immediately!! LOL
.

 

Hey cut me some slack. I live 50 miles from the nearest grocery store and parts house.

I actually have a part can but the **** newfangled spray device failed.

That said, that was funny. I shall purchase two cans so as to ALWAYS have a working model henceforth.

 

It was the fuel pressure regulator. Read about it at http://www.howstuffinmycarworks.com/..._ford_trk.html

Fit my truck's behavior to a T.

Checked it with a jury rigged compression tester and it went over 60 PSI key only on and was leaking.

Ordered a new one that came in the mail today and installed. Started like it used to do with a high idle that dropped at an appropriate time.

Funny story. Bought the truck for $2,100. Has had a basket full of small problem but engine, tranny, and 4wd all seem solidi so can't complain.

Bought the truck during cold weather. Started and ran fine. Warmed up and neither fuel pump would get enough gas to the engine to run. waited for a few hours until it cooled down and made it home.

Fuel filter. Right? Wrong! Ordered one and when I pulled the old one it looked new and was clear.

Replaced both fuel pumps and it ran in hot weather on either tank just fine.

Except for that funny starting, idling, and high fuel consumption.

Apparently the weak pressure regulator was fine with weak fuel pumps but could not handle a new one.

Brakes surge on hard application so rotors are next. Fingers crossed that will be the end for a while. It's been a long list.

BTW, to my surprise I had already bought another can of WD40. Used it to hose down the dust around the regulator before attacking it.

May I please have my card back? NOW!