Backfiring help

[ndnatty]

I have a 79 cj with the 304 in it. Added a Edelbrock performer intake with the matching 4bbl carb, with hedman headers and cherry bomb glass packs. Is it normal for it to have a rumbling backfire when slowing down? It doesn't seem to do it as bad when I put the clutch in before slowing. Is there something I need to do to fix this?

 

[Deerhunter30]

From my experience that is part of the glass pack sound

 

[L33TJ33P]

A bang like a gun isn't normal, but a rumble when allowing the Transmission to slow you is more than normal.

 

[ndnatty]

It's backfire, more than a rumble. Valve job? Or not enough back pressure?? :roll: :?: I'm clueless as you can tell.

 

[Deerhunter30]

I agree that if it is a rumbling backfire, then it is normal. If it is an intnese bang then that is another matter and I am not sure what the cause would be.

 

[Snitty]

i get backfires too... i can't quite find the problem.. a rumble is fine, but like mentioned before, if its an actual bang like a gunshot, then something is goin wrong... could even be a bad fuel mixture

 

[Junkpile]

Exhaust leak or vacuum leak. It could possibly be the timing, but most likely not if there are no other symptoms. Since you changed both the exhaust and intake, you might have a leak at either end. The choke isn't flapping closed is it?

 

[Snitty]

mine is likely due to an exhaust leak at the crack in the manifold

 

[ndnatty]

Hummm, how would I check on the choke flapping closed?? Doesn't do it while at idle or when I rev it at idle, on when driving during deaceleration with clutch out. Had new pipes installed by a shop here, guess I need to get up under it and take a close look at the seals. Thanks for the suggestions!

 

[Inspector-Gadget]

ndnatty,

Since you installed exhaust headers...

Suggest you check to be sure the EGR valve is installed and functional.

A faulty EGR valve or faulty (missing :wink: ) EGR controlling system is a common cause of backfire on deceleration.

Regards,

Gadget

 

[ndnatty]

Inspector-gadget, thanks! I bet that's whats causing it. I did not replace that when I changed out the intake manifold, and the old one was pretty crapped up, just cleaned it up with some engine cleaner and put it back on.

 

[Inspector-Gadget]

Hi again, ndnatty,

You are welcome.

Glad I could be of some help, and I hope replacing the missing EGR valve fixes the deceleration backfire problem of your Jeep.

Obviously, I had a momentary loss of brain activity this morning. When composing my original post. I meant to type….

Since you installed an intake manifold and exhaust manifolds…

No matter, I guess. Looks like you figured out what I meant to say.



Regards,

Gadget

 

[Junkpile]

Wet Okole neoprene seat covers ~NJ

I don't have any EGR system at all. It was removed when the R4B went on. No backfiring here. I 've got headers and 5" bullet style header mufflers. 3" pipes dump right in front of each back tire.

After rereading this, It sounds like normal short-pipe glasspack exhaust rumble. Some popping and cackling is normal when slowing down with the clutch engaged. Like the others said, a backfire is like a gunshot.

 

[88Wrangles]

Ya, the popping/rumbling/crackling sounds is very common with glass-packs and headers. Even longer exhaust, like on my longbed pickup, will make this sound when you let off the throttle