1997 F250 351w E40D

[GentryJr]

So my truck had been sitting for awhile, It cranks fine, but seems to have an issue when I press the accelerator it sometimes doesn’t want to go, also it won’t go over 40 to 45 mph, I’ve changed my TPS, plugs, distributor cap, rotor, fuel filter, oil, and oil filter along with the air filter, now today I was messing around with it, I tried to get it to go, I started in low gear 1, then shifted to 2 then around 30 mph to 3rd, it seemed to work a lot better but still won’t go over 40/45 mph, I also was thinking that maybe it’s a transmission issue, because today it threw a check engine light, I couldn’t check it cause I don’t have a reader, but if I’m not mistaken I believe it’s a 4 gear transmission, so I ordered an transmission output sensor and some new spark plug wires today, I also was thinking of changing the mAp sensor but didn’t want to get to crazy, now on these transmissions is the transmission output sensor for my year on the differential it’s a 3/4ton? Any help would be most appreciated as I really love my baby

[GentryJr]

Also it’s an automatic so when I say shifted I mean low gears to drive

[glc]

I would highly suspect the MAP sensor. Also, I'd check the cats and the rest of the exhaust for blockage and excessive backpressure. You definitely need to read the codes, parts stores generally do that for free. However, most parts store scanners can't read transmission codes if it's OBD2.

[GentryJr]

Thank you sir, I’ll do that