So this has been happening even since I got my project Banshee running (I bought it without knowing if it ran or not). I completely rebuilt the engine and now it runs fine, except it wont idle and when I let off the gas to coast and then gas it back up, it backfires. I figure that the two are related, so i need to fix this. Ive played with the idle screws, the idle air screws and I switched the slides. Nothing. It seems to run fine as soon as that TORS switch clicks off. This is really getting annowing and the neighbors dont like the "gunshots" that keep going off. Help

 

well it sounds like you mite have a crack in your rubber boot between the carbs and the intake..Or you exhaust is leaking around the header leting in air..couseing it to back fire..but the idleing sound like you got a leaking carb boot...

 

but if it was a crack in the boot, then wouldnt one side try to idle?

 

The other side would slow it down, the pistons are connected.

 

so then the boots are most likely the cause?

 

Yea the boot is most likely the prob as driverdoyle said and if its not cracked make sure it has a tight seal all the way around and make sure it has a hose clamp on it...I also had a prob with my gaskets on my head pipe on my ds650 and it would let cold air into the exhaust and would backfire due to a vacuum being made...My other guess would be that the timing is off but you said it idles fine so i don't think that would be the cause of the problem in this case...just pretty much do wat doyle advised and I think the problem will be solved.

 

428 mustang what year of a mustang do you have my dad has a 1968 428 cobra jet with a police interceptor and a convertable which ford doen't admit to making but the vin says that it does and is all original.

 

the backfiring on deceleration is a lean idle circuit, either too much air or too little fuel flow. Think about it- when the engine is running fast, and then you close the throttle, all the fuel and air that goes into the engine must go through the idle circuits, right? so, check your air intake boots over good for tears or cracks. If they are ok, start checking over the carburetor adjustments, it's gotta be something simple.

 

so i was thinking these two were linked because i figured that it isnt idleing right, most likely not getting enough gas/air through the idle circuit. This mean that it wont idle and the backfires are the small amount of gas that goes through and detonates in the pipes. This sounds like I just diagnosed my problem, so my question is am I right and if so, how do I fix this. My floats havent really been working right lately, so might that be some part of this?

P.S. bombrider04, my friend used to have a big block mustang, and I fell in love with the car and it has been one of my favorite classic cars ever since.

 

nice hope you figure out what the prob is