Exhaust backfire on decelleration
 

Hi,

I just rebuilt a '90 3.0 and installed it in a 4X4 truck. The truck runs fine and has decent power (for a 3.0 W/33's). During the rebuild I also installed new dynomax cat-back exhaust w/o a converter. I notice an exhaust backfire during engine decelleration (w/o brakes) in lower gears at slower speeds. I can eliminate the backfire by clutching thus dissengaging the engine from the drivetrain. My guess is that the backfire is from unburned fuel igniting further down the exhaust due to decreased exhaust pressure.

I have never heard the rebuilt motor run with the old exhaust I was wondering if it was normal for a little backfire on hard decelleration in gear with some aftermarket exhaust systems?

Anyone else have this problem with new exhaust/ no converter?

Note: Ign. timming is correct.

check that your dash pot still works properly. When the throttle plate is suddenly closed it holds open the plate for a little bit, just shy of closing. This makes the engine run lean for a little bit and could solve this problem.

what will DEF solve this is putting that cat back on!!

Go to performance products and get yourself the carsound hi flow cat, I have one and it works great. And the best part is no horrid smelling gas fumes while driving. (And theoretically helps the environment, but with all the other countries not having em, i think its like pissing into the wind...) My cat is there so long as my truck is NA....:D

Hey, good idea Bumpin' Yota.

Even if the dashpot is working properly, I should be able to fine tune how far/long the throttle plate is open adjusting the air to fuel ratio to the match the exhaust "backpressure". It might not be as specs. state but should work to eliminate the backfire.

Thanks

catalytic converter are like $70 dollars alot cheaper than getting a fine for not having one .... so you have aftermarket exhaust ?

Yes, I have pacesetter cat-back exhaust. Had a brain fart; stated above I have flowmaster, but that is on by other truck.

Don't really wish to get in the converter debate. Everybody has there opinions which I don't wish to change and I'm probablly not going to change mine. Plus, I highly doubt I will get checked where I live.

yea id hate to see this turn into a "cat" fight! :P:P:P (pun intended!)

:D

backfires make for fun driving through the tunnels in Baltimore!! just a good way to scare the ÅÅÅÅ outta some people.

Yea, but I'd hate to give some poor old lady a heart-attack.

Update
 

I adjusted the dashpot today and it seemed to take care of the problem.