bucking and backfiring

[coolcoupe]

Just wondering where a guy would do with a 1947 car (stock) when the car idles really nice but giving it the gas it bucks like its running out of gas, once its doing over 20 mph and you let off the gas it starts to backfire? Any ideas?

 

[petehoovie]

I'm thinking a bad condenser....

 

[FlatheadTed]

Dirt in carby ,Could be low on voltage check if the spark is yellow on revving it up ,Ted

 

[rotorwrench]

It could be a bad condenser since most available now are not made well. The points are generally burned if the condenser is failing.

Sounds like the idle circuit in the carb is working OK. The main metering circuit may have some blockage. The accelerator pump might not be working as it should. There also could be a power valve problem. The float valve could have a problem with blockage or adjustment of float is off.

The fuel pump out put might be off or maybe a partial blockage or a crack in the fuel supply line circuit allowing air bubbles in.

All are possibilities that will have to be eliminated, easiest one first till it's fixed.

 

[Ken Bull]

I had a simular thing and it turned out the vacuum hose to the wiper moter went bad .

 

[Tinker]

Same thing happened to me. Hesitation,backfires, and misses at low rpms.

A New NEW condenser. second new one.

MMO down the carb for a bit at idle. Then fresh gas and MMO in the tank.

Drove it 10 plus miles and it leveled out. No issues now.

 

[coolcoupe]

Thanks guys, I will start at one thing at a time until I get it !!