dmelhorn

So I bought have a 85 Toyota pickup I got it a year ago. It was having a hard time starting. I ended up rebuilding the carb. I don't have that much experience with rebuilding them, so after I got it in I started having issues with it having slight back fires. Now it is getting worse and worse. Happens most when the truck is at lower crusing Rpms. Like when I shift into 4 gear it will do it. I can even use 5 th gear anymore. I have a feeling it has something to do with the carb. But I did check the timing it is right. So I am not sure what it could be any suggestions?

xxxtreme22r

How did you check the timing? Normally backfiring is due to timing.

dmelhorn

I used a timing light and the light was right on the mark on the timing belt.

dmelhorn

I mean on the pulley

xxxtreme22r

with or without vacuum? Should be 0 without vacuum @750rpm and about 12-15 degrees with vacuum at normal operating temp.

dmelhorn

It was without vacuum. I am not the most knowledgable at this part of mechanics but being it was right at the mark that is 0 right?

rokblok

iTrader: (1)

Kinda also sounds like plug wires could be breaking down. Or some ignition component. All plugs, wires, dist cap, and rotor are new?

Does it do it only at hard throttle but low rpm's(accelerating)? Or if you are letting off the throttle does it still do it? Idle is good?

dmelhorn

All the wires, plugs are newer. And I believe the cap and rotor are as well, they look that way anyways. It does it a lot most when it is still warming up. But it will start to do it after I shift into a new gear. So say I am in 3rd accelerating I will shift into 4th, then as it is now lower rpms it will start to backfire. And 5th just is unusable as it puts it into probably the lowest rpms.

I have been looking around at some info and I am pretty certain it is a intake manifold backfire not an exhaust. It is throwing a lot of sute up into my hair cleaner.

I am going to try and check the timing again, double check.

But is there any way this could have something to do with the carb as it seemed to start after I rebuilt it. Did I do something wrong. Or is this just a coincidence?

dylan_doomsday

Generally, if the timing is right, an intake backfire is caused by a lean mixture (the combustion chamber is hotter causing the fuel to combust without a spark) and an exhaust backfire (technically called an "after fire") is caused by a rich mixture (the excess fuel is burning off in the exhaust). Where you just rebuilt your carburetor, I'd check your mixture, in particular your idle mixture since it happens primarily at low RPMs. If it were me, I'd richen it up a bit at a time and see what happens. Running rich is far less dangerous than running lean.

dmelhorn

Great I will give that a try.