so my buddy Josh got this '81 2wd wagon from our buddy here on the board and it has some issues. First off, when it gets to operating temp, it doesn't want to idle. Now the carb was rebuilt so maybe its a tuning issue or something. Problem 2, it backfired really badly when the motor is revving down, also me thinky its a tuning issue even though it was timed with a timing light so I'm not sure. Any help would be appreciated so lemme know guys:D

It could be that the Anti-Backfire valve has failed, because it sounds like it is not doing its job, or the EGR system is screwed up, or both.

Check those then retune the carb.

could be the ABV

 

but don't rule out the AIS ( Air Injection system)

notorious for causing major back fires.

 

These started being used in 82,but it may have one.

 

note if the reed valve in the AIS is bad it can melt the silencer and

 

the carb has been known to

ingest the melted plastic.

 

see this link, it talks all about it

 

AIS defined and described

could be the ABV

 

but don't rule out the AIS ( Air Injection system)

notorious for causing major back fires.

 

These started being used in 82,but it may have one.

 

note if the reed valve in the AIS is bad it can melt the silencer and

 

the carb has been known to

ingest the melted plastic.

 

Didn't think about the AIS b/c I never had that kind of trouble when mine was carbed. Glad I didn't tho

oh I forgot to add this motor came from an '86 Brat and has the '81 manifold and carb on it. I don't think it's the AIS system cause I found out last night before I went to work, that it really wasn't timed with a light, just by ear..... I hate it when people lie to me...