Sluggish 351w
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Joined: Dec 2014
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From: MN
Sluggish 351w
Hey guys, hoping to get some thoughts on my truck. It's a 93 f250 351w 4x4 3.55 gears with 305/70/15 tires. The truck runs and drive just fine, just seems very sluggish. It will kick itself out of OD with the slightest incline or small amount of head wind. I have been doing a lot of work to this truck, so here's a list of things I've done recently that may have an impact performance wise. New oil pan, valve covers, shorty headers, rear tank with pump and sending unit, fuel pressure regulator, MAP sensor, plugs and wires, cap and rotor, fuel and air filter. It has dual exhaust with no cats and flowmaster mufflers. Couple years ago I daily drove a 94 Broncos with the same motor, so I am familiar with the kind of power it should have. Any input will be greatly appreciated.
thnx
thnx
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From: MN
Forgot to mention the only issue I've noticed so far is that it starts kinda hard when warm. Cold it will fire right up, but when warm it cranks longer and kinda stumbles as if it's not getting fuel. Usually I just press the gas pedal just a little and it will then fire up. Other than that it will idle fine all day and drive down the road fine, other than feeling kinda like a dog
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From: Ottawa, Ontario
15" tires on an F250? If that was a typo and you meant 16" then that is a 33" tire which is a bit big for a 5.8 truck with 3.55 gears IMO, you would get better performance and milage if you locked out OD on the highway.
You need to check codes and fuel pressure, don't assume anything. Also check timing with the spout removed to disable computer advance, it should be at 10deg BTDC.
How big is that dual exhaust?
You need to check codes and fuel pressure, don't assume anything. Also check timing with the spout removed to disable computer advance, it should be at 10deg BTDC.
How big is that dual exhaust?
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From: MN
Sry, typo in my part. They are 16 wheels. Exhaust is 2.25 inch duals. I will check the timing and fuel pressure. What kind of pressure should I be expecting? I know the tires aren't helping anything at all, just didn't think it would make that big a difference.
thnx
thnx
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Fuel pressure should be 30-40psi within a couple primes of the pump before the engine is started, 32-35psi with engine idling and 40-45psi if you remove vacuum from the regulator. What was stock tire size.. 235/75R16? That is a 30" tire so 33's will be noticable. The correct gear ratio for these small V8 HD trucks is 4.10 IMO, got that in my E250 with the 4.6 and it drives great on the highway.. climbs many grades without even unlocking the TC and gets better than average milage.. mid to high teens.
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Ok I finally got a chance to do some digging. I checked for code and all I got was 111, so I'm good there. Checked fuel pressure and got 30lbs with key in on position pre start. 32lbs at idle and 40lbs when hose pulled off fpr. Just for kicks I did the same test on the other tank and it was basically the same, about 1 lbs higher on each is all. I will try to get timing checked soon.
thnx
thnx
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Something I noticed today that I forgot about... It looks like the po disconnected the air pump and if I remember right from my previous trucks is that there is supposed to be a bunch of rubber hoses on top of the motor and other stuff that I thought was maybe related to that. Well all that is gone on this truck, and I also noticed 2 vacuum lines that go to nowhere. Any idea what they're for? Or what I should do with them?
thnx
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Tuned
Joined: May 2017
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From: C-town,MD
As Conanski said, you need some gears. Put the stock tire size back on there and see if your low end power doesn't pick right up.
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Are those vacuum lines connected to the TAB/TAD solenoids there next to the coil? If so those lines need to be plugged... they're not open all the time but when the computer activates the solenoids you would have a vacuum leak.
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From: MN
Well I finally got some time to tinker on the truck. I got those 2 vacuum lines capped off and I checked the timing. The timing was only at 7°! I bumped it up to 12° and it's like driving a whole new truck. Thanks guys for all the help! Much appreciated
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