Hello. My 91 f150 has acceptable acceleration from 0-40 or 45, but getting up to highway speeds can be a bit slow. For safety reasons, id like to be able to punch it more on freeway on ramps. Since it jumps ok from 0, im wondering if typical performance issues like bad/old spark electrical system would be less likely for this situation. Im not 100% sure when the spark plugs were changed, since it bought it about a year ago, but i believe the guy i bought it from did change them less than 5k miles ago. Pretty sure he mentioned the plugs are relatively new.

Not looking to burn rubber anything, id just love to be able to punch it a tad more in case of emergencies. I have no idea what this thing felt like brand new, so i have no frame if reference to what it should feel like. Maybe this is just how its supposed to be. It would be amazing just get an extra 10% power or so when you have to floor it. Any ideas on where to start?

 

Compared to today's vehicles, 80s and 90s Ford trucks are relatively low on horsepower and torque, so some of your situation may be that reality.
The last full sized truck I owned, was a 1991 (other than Ford), that made less than my current truck's 185/270 horsepower/torque ratings. I never thought once that that truck was underpowered, but I was comparing it to '89 and '90 V6 powered mid size trucks.
I haven't had my current truck on the road legally since 2015, but my goal is to get it running as close as possible to factory condition.
I would look at tire size, gear ratio and automatic transmission function in your case.

 

Best advice is to properly maintain your vehicle's systems as spelled out in your owner's manual. .If your vehicle's fuel or ignition systems are running on the ragged edge, they will affect your engine most during peak demands. Low fuel pressure, a loaded up fuel filter and excessively worn spark plugs are the first to come to mind.
Your final rear end ratio will greatly affect the performance you seek at a cost of fuel economy.

 

Thanks for the message! Seems like final gear ratio is the common denominator from the responses ive gotten. I'll start looking into pros/cons, and price. Seems like a big job so not sure if I can pull that off. But really good to know what I'd need to do.

 

Good advice, thanks! Final gear ratio adjustments might not be in the cards for me. But I'll start looking into fuel pressure, filter and to be sure check the spark system. If that doesn't help much ill start thinking about final gear ratio. My fuel economy is already not spectacular, but it runs great and nice and quite at 65 so I'd hate to tinker with that. Thanks again for the advice.

 

What axle ratio do you have? And what RPM is it shifting at when you are trying to accelerate hard? If you are cruising and then punch it, does it downshift like it's supposed to?

 

Oof. I just realized that it doesn't down shift when I step on it . It's been a while since even had an automatic and that makes 1000% sense and kicking myself that it never occurred to me. It should downshift when i floor it, but it definitely does not. Just from a quick search, it sounds like a bad throttle position sensor can keep your car from downshifting while accelerating. I'll check on my axle ratio and report back and get on the highway tomorrow to watch for exact speeds when switching gears. I never really turned off overdrive either, would it be recommended to use for merging on freeways? Thanks for the message and questions.

 

My throttle has always seemed a bit loose, and my gas pedal is fairly close to the floor. It's definitely not a permanent solution but I attached an alligator clip to my throttle cable so the gas pedal rides higher and theres more room to floor it. Sure enough, the transmission now downshifts when you hit the throttle hard. It's not amazing acceleration but its a massive improvement. Now I just need to figure out why there's so much slop in my cable.

 

The cables stretch over time. The fix is to either replace it or use a spacer to pick up the slack. A lot of people use zip ties as spacers. Mine has two of them stacked next to each other and it drives great now.