Hey guys, new to the YotaTech fam. I’m going to be honest and upfront. I’m not much of a mechanic in terms of diagnostics and symptoms so bear with me, please.

I have a 1986 toyota Pickup 22r(carbureted). My issue is I can’t get up to highway speeds. Usually tops out at 55mph. When going downhill, it will obviously increase speed but drops back down once on level ground. Anyone have any insight on where to start looking and checking?

 

There could be a lot of causes and more info would help.
Is the truck 2 wheel drive or 4 wheel drive, stock wheels and tires or taller off-road stuff, Type of transmission (4 or 5 speed, manual or automatic), mileage on the truck, how long since the clutch has been changed (time or mileage or BOTH), at 55 MPH is the engine running well (no misfiring), carburetor ever been cleaned, rebuilt or replaced and when, ANY recent service done to the truck, what type of gas are you using (ethanol blended gas or non-ethanol), has engine timing been checked lately, any strange engine noises that are new, how old is the battery.

Answers to these would help me to maybe narrow it down some. If it's 4 wheel drive & the transfer is in 4 Low you aren't going to get highway speeds out of it. Tall, off-road tires can also cut down top speeds. On an Auto Trans your torque converter could be slipping (rare). If the clutch is worn it could be slipping at higher RPMs/engine speeds. Any thing recently done to the truck could have knocked loose a wire, a connector or a vacuum line. Use of Ethanol blended gas with old fuel lines can cause the insides of the line to degrade, releasing small rubber particles that can clog up carburetor passages or cause fuel line leaks (this happened to me). Engine timing may have changed due to worn or broken parts; the timing chain guide is known to sometimes break, causing excess slack in the timing chain, which could change the timing. Any strange ticking or clacking sounds near the front of the engine could indicate this. An older battery could have internal problems which can affect the whole electrical system.

These are just some of the things I can think of off the top of my head.

 

You should still fill in the blanks as 13Swords mentioned, but one quick check that could save you a lot of headaches is to see if you are getting full throttle travel. Have a helper mash the gas pedal to the floor and then try to move the throttle linkage on the carb. If it has more travel than you get with the pedal you need to adjust the cable linkage.