I been trying to figure this problem out for awhile but I don't seem to know whats wrong... I don't know if its normal or what... I have a 89 240sx with a SR20DET swap... The car always backfires when I start to slow down at a stop... It usually happens when I'm in 2nd gear and as the RPM starts to decrease when it gets to about 1500 it would make a loud bang noise... when I say loud its like shotgun loud... this doesn't sound normal... but if any1 can help me I would be very thankful...

Roger

 

its normal, have installed an sr fuel pump and adjustable fuel pressure regulator yet

 

most of the sr20's I seen doesn't do this it would make a puttputt noise but not a loud bang. half says its normal the other says its not. all i can say is that it doesnt sound normal and im sure it doesnt come off the lot sounding like crap.

 

I had an N/A B18C in my old Honda and it would do it all the time... Its nothing to worry about..

 

your running rich. this isnt normal. mine dosnt do it. install a fuel pump and regulator and maby a super afc and that should fix it if not giv u more power

 

Its because you are running rich, but its kinda sorta normal..if you have a blowoff valve that's open..it doesn't have anything to do with the fuel pump, and I guess getting an adjustable regulator might get rid of it, but isn't the source of the problem..

recirculate your blowoff valve..your open bov is making you run rich because of the fact that it's open..its letting metered air back out of the engine when its under vacuum and the blowoff valve is open (i.e. when you are off the gas decelerating)..hence it adds as much gas as it thinks is there..blah blah blah, you probably already know this.

my car did the same thing, loud as hell. I recirc'd the blowoff valve, and it hasn't done it one time since

 

thanks alot dustbunnie... one more question is it safe of the motor to just leave it like this?

 

b2stud its normal... the car is cooler like that...

 

isn't it gonna kill you cat?

 

he doesn't have a cat....

 

stop using my account to post. and if your running stock turbo all that upgrade is more for show than go. stock parts are usually better quality and more accurate anyway. use the stock bypass instead of recirculating the bov.

 

In certain cases yes, (i.e. clutch slave cylinder, filters, etc...) but the stock recirculation valve I don't think so. Its notorious for leaking. A quality BOV properly adjusted and recirculated to the intake while not a necessity, will perform better than your 15+ year old stock one.