Ok Im stumped now.. My truck has a stumble to it Its only at very light throttle. I'd say about 1/4 throttle, If you give it gas it pulls hard and not a problem with it, At low throttle in all gears it jerks and stumbles some kinda bad. I thought it needed a tuneup So I put new plugs and wires. Cleared up at first...But once its warm it goes to stumbling bad, especially in traffic. So I replaced the fuel filter...It def. needed that but problem is still the same. Like I said, you give it a little more throttle, its totally fine. Its carbed, and the carb was rebuilt before I got it. And it idles and starts like a champ and pulls and drives great except at low throttle...Like in traffic or slow speeds in subdivisions and stuff...Any ideas?

 

I'd be searching for a tiny vacuum leak from somewhere. Or check the EGR valve.

 

I had a similar problem recently. Replaced my o2 sensor a the problem went away.

 

It idles perfect though, not a sound out of it, its only at low throttle...And mines carbed...no o2

 

This is common with carb engines; have your accelerator pump checked. It sounds like it's dumping too little or too much fuel in when you apply light throttle. if you look into the carb when you're pushing the throttle, you'll see a fine squirt of fuel--that's the pump doing it's job. If it gets worn, sometime is puts too much or not enough fuel in that squirt and causes stumbling like you've described.

 

I've rebuilt these carbs on older Toyotas before, I know accelerator pump problems. I might conisder upgrading carbs if its the problem