What causes this. My car will back fire from the exaust when I first crank it up and its just sitting there ideling. Also when I am driving it will do it when I coast at about 70MPH and let off the gas and lightly put it back on it will make a couple pop noises. Oh btw I have a manifold exaust leak and the rest of the exaust is stock besides the fact that the muffler was replaced with a Y Pipe

 

leak could be part of the problem......little backpressure b/c theres no muffler....any cats??

u always need a sometype of backpressure.......my car only did it when it was first started and reved it up when cold after it warmed up it didnt do it ..

some say its b/c of thewarm air touching the cold exhaust pipe....like the same way thinder is made cold and warm front colliding etc u should know no need for me to teach u earth science lol

 

yeah mine does that too. it backfires in the morning when its cold usually just after i fire it up or right when i shift as i pull out of my driveway. i thought that i might need new o2 sensors or something, mabye unburnt fuel hanging around in the exaust????

 

It will always pop when cold.

An exhaust leak will cause it to possibly pop even when it's warm.

Dan

 

Exhaust gases/mixtures, whatever, build up in a hot exhaust manifold..bla bla bla..lol..

 

??? Confused as to why you quoted me before your reply. ???

Dan