1996 F 150 w/ EFI (straight 6) 300 cid w/5 Speed Trans.
It get's poor gas mileage and when weather is 90 degrees or above you drive 10 miles
or less then starts running sluggish and when you shut it off and try to start it again it
runs very rough and takes awhile to pick up RPM. After it picks up RPM's motor will
smooth out but when driving still runs sluggish. The motor is not over heating I know,
about 6 months ago I replaced water pump, thermostat,fan clutch and belt it runs a lot
cooler than it did. I've been to part stores to get them to hook their code readers up to
it but they won't read it for some reason. I live on a small fixed income and can't afford
a lot of guess work. I hope you can help......Thank You !
I've run into a few issues with the 300 six. First is the intake/exhaust manifold gasket. Because there is so much weight hanging off of one side of the motor and because the two manifolds run at different temperatures along side of each other, the nuts can loosen, manifolds warp, gaskets fail and vacuum leaks occur. In my opinion: those Manifold studs and nuts should be checked every year. More often if you haul or tow. The other big concern I've seen is a failing Ignition Module. Their faults are heat related. Especially when you allow it to cool off and it starts up and runs fine. Realistically, this is a big 6, I hope you mean worse gas mileage than usual because it doesn't get great mileage to begin with. It's likely that the parts stores don't have or don't know how to read codes from your truck because it's an older OBD1 system and, lets face it, most of the people in parts stores are Retail Clerks, not mechanics. So, there's a few things to look at but you may consider calling around to a few shops (yeah, the dealer too) and pricing a diagnosis - some shops will soak up the cost of a diagnostic in to the repair. You're right though, guessing gets expensive.
Thank You...Tracy, I think I will try a shop and let them run diagnostic. In the long run this may be cheaper. Thank You again my Friend !
You are very welcome.
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