Truck can't keep up with traffic
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Senior User
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Truck can't keep up with traffic
So my 1990 f150 4x4 4.10 5.0 efi 5 spd is slow. I know its a 5.0 but this is ridiculous. I have almost no power away from lights (slower than an 18 wheeler or bus). I can only hit 65 mph downhill and reving the truck out at 2500 rpm. I've done a complete tune up (plus, filters, wires, etc) and not much better. I run 32" bfg all terrains. I lose so much power on hills even when I drop it into lower gears. If I hit a hill at 55mph I drop down to 45 reving it out. Is this normal. I can keep up with traffic. I almost have people rear end me a lot.
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Fleet Owner
Joined: May 2009
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From: Gilbert, PA
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Postmaster
Joined: Aug 2005
Posts: 4,728
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From: Cleveland, TN
Maybe you need shoes with more grip on the soles to wear when you're pushing!!!!!!! Seriously, I'm with Brad here, check that converter!!!!
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Lead Driver
Joined: Aug 2006
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From: Sand Lake, MI
Check the fuel pressure lately?
And to further Brad's suggestion, easiest/quickest way check CC for back pressure would be use of a vac gauge, opposed to taking the system apart to check it.
And to further Brad's suggestion, easiest/quickest way check CC for back pressure would be use of a vac gauge, opposed to taking the system apart to check it.
Laughing Gas
Joined: May 2004
Posts: 1,062
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From: Dallas, TX, USA
I had an 86 that did the same thing. It was a fuel pump that would start failing when it got hot and let the EFI pressure bleed off. So, yeah, check to make sure you have at least 30psi at the rail especially when revving it to 2500 or so.
Senior User
Joined: Dec 2010
Posts: 295
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From: Ca.
This is off the wall here but i'd strip it of all it's junk at the front of motor. Go with manual steering. That result is more unbridled power Install an electric fan, too. Consider an ignition curve box where you control the advance timing from the cab. Those above ideas are also good.
Laughing Gas
Joined: Dec 2007
Posts: 959
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From: Imperial, MO
On a 4WD with 32's? 
There's obviously something wrong with the truck if it won't even reach 65MPH on a flat surface with 4.10's and 32's. OP, what do you mean by "reving the truck out at 2500 rpm"? That isn't a particularly high cruising rpm or anything. How many miles are on the truck? Stock exhaust?
There's obviously something wrong with the truck if it won't even reach 65MPH on a flat surface with 4.10's and 32's. OP, what do you mean by "reving the truck out at 2500 rpm"? That isn't a particularly high cruising rpm or anything. How many miles are on the truck? Stock exhaust?
Post Fiend
Joined: Oct 2003
Posts: 6,214
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From: New Jersey
Why not start with the simple stuff.
Measure vacuum at idle, and at a given RPM.
Measure fuel pressure.
Measure oil pressure.
Measure cylinder compression.
Low figures on any of those things can tell you a LOT about what is wrong, codes or not.
Measure vacuum at idle, and at a given RPM.
Measure fuel pressure.
Measure oil pressure.
Measure cylinder compression.
Low figures on any of those things can tell you a LOT about what is wrong, codes or not.
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There's obviously something wrong with the truck if it won't even reach 65MPH on a flat surface with 4.10's and 32's. OP, what do you mean by "reving the truck out at 2500 rpm"? That isn't a particularly high cruising rpm or anything. How many miles are on the truck? Stock exhaust?[/quote]
197k on truck. Unknown on motor as its a used replacement. The truck only really revs to 3k max if its not first or 2nd gear. Aftermarket dual exhaust with flowmaster to y pipe
197k on truck. Unknown on motor as its a used replacement. The truck only really revs to 3k max if its not first or 2nd gear. Aftermarket dual exhaust with flowmaster to y pipe