Quadrajet problems.

[irishman999]

This is going to get complicated...

The truck is a 85 gmc high seirra, it came with a 305. The 305 got switched out after wearing out for a 305 out of a burned down car in the early 90's.

While preparing this truck for the road i was not planning on using any emission vacume lines so i unhooked and discarded most of them.

I got my quadrajet rebuilt and put it back on not realizing wich vacume lines went where because im still a dumb young kid i guess and threw away most of the hard lines connecting to the carb and various emmision components.

So i have the chilton manual with a vaccume diagram, i started running new vaccume lines but since i have a diffrent motor in the truck than origional i think i have diffrent emission components than what origionally came on the truck.

i started targeting the vaccume problems starting with the carb, the engine sounds like the timing is off, it idles rough and backfires a little bit when i rev the engine high.

I ran a vaccume line from a port on the back of the carb to the distributor and it almost seemed to help the timing issue, ran a little smoother and did not backfire as much.

The strangest thing is the vaccume port on the front of the carb, its pulling vaccume and if i hold my finger over the port when it is idling the engine dies.

Is there anybody very knowledgable with the quadrajet that could tell me what the vaccume ports are supposed to supply vaccume to?

[datguysaL]

how does it act without the vacuum lines?

[irishman999]

With no lines connected its idling rough but runs ok, as i throttle up it pops and backfires. I connected the vaccume advance to one port that didnt have suction at idle and it seemed to rev up beter but still popping a little bit.

There is one vaccume port on the front that will kill the engine if i hold my finger over it.

i think the tank is really low and its running on the nasty old ass gasoline, could that be cauing the popping?

[datguysaL]

yup, old gasoline can be the cause, and also timing. clean out that fuel first.
lemme know how it changes.