Hello all, been a long time since I last posted but I have been lurking around for a long time. So my truck, 1996 f250 HD extended cab short box 4x4 7.5 5spd 4.10 gears. I want to try and not be long winded but my question is odd so I'll do my best. Truck is in good shape and it also runs well, no obvious issues with the way it runs. Truck seems somewhat powerful with the motor, gear combo. My issue is that out of nowhere it will feel like a different truck in a good way, it will feel all around more powerful, crisper throttle response, better acceleration, etc. I am not crazy I'm 100% certain of that lol. Now the truck never runs bad, meaning if someone who wasn't familiar with it got in and drove it they would probably say it ran well and felt plenty strong but since it's mine and I'm familiar with it I can tell when it's running "extra" good. I have not been able to make any connection between atmospheric conditions or anything like that that would cooralate with an improved condition. I did a tune up last month with good quality wires,cap,rotor o2 sensor. Hooked timing light up and checked it with sprout in and it was advanced and then I removed the sprout and base timing was dead on at 10 btdc I actually played around and advanced it about a degree and a half and picked up a little benefit from it. So I was generally pretty happy with it. So just recently is when I started noticing that it would run better at times. So my question I guess is has anyone else ever had a situation like this? And does anyone have any idea what would be causing it? I'd like to know because I would love if it ran in the "improved" mode all the time. I should also add that I switch between front and rear tank and that doesn't seem to affect anything. When it runs like that it makes no difference what tank I'm on. I was thinking at first maybe a weak pump etc. like I said tho just to be clear the truck never runs obviously bad in any way. I apologize if I'm long winded or not clear enough and I tried a few different search parameters and could not find a similar question or at least wording that was similar. So I would love any opinions of what might cause such a thing

 

I should add that for some reason fuel pressure is on my mind and I think I should pick up a gauge so I can test. I'm wondering if maybe fuel pressure regulator is acting funny. Is that a possibility? Meaning could fuel pressure be low but not low enough to necessarily make truck run poorly but then increase and make it run like it probably actually should run all the time? I had bed off last year about this time of year when I did a ton of work. At that time I replaced both pumps, I had both tanks out and they were both very clean on inside so I don't believe the socks on pumps are clogging up, fuel filter was also replaced at that time. Being that both tanks were clean I'm not thinking the filter is the issue but I picked up a new one yesterday anyhow because it has been a year and it's cheap and easy so might as well rule it out as well. So anyhow I just thought I'd add that about the tanks and pumps

 

Well, tony b., I've noticed the same subtle performance differences in my truck. It's a 97 F350, 4x4, RCLB, 460, ZF5, 4.10, Gear Vendors OD, underdrive pulleys, elec fans, KN drop-in, hot Accel coil, wires, cap, copper Autolites @ .050, timing @ 14-16*, Flowmaster 3" SISO, stock converter, 265/75/16 tires, no lift (actually lowered the back with 2" F250 blocks). On E zero gas I get 11-13 mpg winter, 13-15 summer. I cut out the intake "horns" but seemed to lose some down low "tip-in" snap with no gain up top...so I reinstalled them. I've scanned, checked fuel pres, sensors, no CEL ever...I keep this unit in top tune. Seems that when the engine is cool (not cold) along with cooler air stream, probably still in open-loop, running on look-up tables, more timing/fuel for driveability...that's when mine is the guttiest. Warmed up in closed-loop, I suspect the computer pulls timing/fuel slightly to minimize emissions, plus hotter air stream...ergo, more sluggish performance. We know our trucks...no one else would notice. Most any engine will make more power when "cool" than when heat soaked, I guess. I've always wanted a tach-like guage to show real-time ignition timing as I drive...just for kicks. I suppose some of the latest and greatest tuning systems embody such a capability. BTW, this my first reply. I like FTE and have garnered much useful info over the past few years.

 

So I'm not alone in thinking this. What you mention about the computer running open loop vs closed loop etc is along the lines of what I was thinking about. I was wondering if there was something correctable with the computer, meaning I was wondering what was cause of the computer changing parameters. I know it's supposed to change and adjust for different conditions I just wanted to be sure there wasn't something that needed fixed to make it more consistent. Oh and also I went ahead and changed fuel filter on Saturday and I was very surprised to find how restricted it was after almost exactly one year on the truck because of how clean the tanks were when I was in them one year ago. Must be a lot of crap in the station I stop at regular. Well thanks for your reply. This forum is good if you have s problem and get replies from guys. There are some very knowledgeable folks on here.

 

Tony. b...If you get your fuel issues fixed, I'm sure it's timing. I doubt there is any thing "wrong" other than just the lazy advance curves programed into our systems. This is fine for heavy work and low emissions...but not fun when we're playing. Too bad our 460's don't have knock sensors. Back in the day I had an '85 Ranger, 2.3, 5 speed...set static timing at 20-22*, then the KS would pull timing at higher RPM as needed...no ping. Unplug the KS and it would ping like crazy! I ran these settings for over 100K miles with no ill effects...sure helped the low end snap! I've thought about putting an after-market dist in my 460...fully adjustable mechanical and vacuum advance. Is that possible? Or get the computer reflashed. Actually, I'm quite pleased with the way it runs...I just don't have the "fire in my belly" for performance like I did back in the 60's during the muscle car era. Here's hoping to continue this thought experiment...

 

I have the same truck as the OP, and I've always noticed it has significantly more power on a cool damp day. I live a 6000 ft above sea level, so I've always assumed that there's more oxygen in the air making the truck run better.

 

...and our bodies, as well. More O2 per gulp. "It's the MASS, baby...not the volume".

 

I have also noticed that on cool damp days that it runs stronger that's for sure but what I've been noticing is beyond just that. But that definitely does affect power. I really notice the difference on those cool damp days with my 60 ho Johnson 2stroke outboard on my boat. Actually ends up running a bit lean because the air is so dense. I always notice this later in the summer season in the evenings once the cooler weather starts to set in. So it's definitely a fact that atmosphere can affect an engine. Really notice subtle weather differences with the nitro engines in my r/c trucks too they run different one day to the next.