Backfire on decel
Thread Starter
Heel & Toe
Joined: Jul 2004
Posts: 15
Likes: 0
From: Seneca Falls NY
Backfire on decel
I've had this problem for a while, but only when I push the clutch in. Seems to be worse when cold. I've removed precats and replaced main cat. Also done:Magnaflow catback, Ford injectors, complete tuneup, new ecm, k&N cut box, new fuel pump and filter(s), CTS, ignition module, and new egr.
I was thinking about adding aftermarket chip to advance timing and add fuel. I'm thinking this might solve the problem because that is what worked on my EFI Harley. I added louder pipes and K&N and had backfire on decel. This was fixed by adding fuel on decel via a EFI tuner. The theory is that more fuel gives more compete detonation in the chamber.
I assume that this would not be as much of a problem with automatics.
All I hear on this board is what a waste of money the chip mods are on a lightly modded motor. Thoughts?
I was thinking about adding aftermarket chip to advance timing and add fuel. I'm thinking this might solve the problem because that is what worked on my EFI Harley. I added louder pipes and K&N and had backfire on decel. This was fixed by adding fuel on decel via a EFI tuner. The theory is that more fuel gives more compete detonation in the chamber.
I assume that this would not be as much of a problem with automatics.
All I hear on this board is what a waste of money the chip mods are on a lightly modded motor. Thoughts?
Le Mans Master
Joined: Dec 2000
Posts: 7,839
Likes: 22
From: San Diego, Ca
Usually occurs because the air pump is still delivering air to the CAT - kinda frequent back in the '70's when the OEM's didn't know how to cut the air flow. It should divert overboard when your lift your foot off of it. Otherwise, the extra air ignites the additional fuel it gets when you let off the gas. You need to troubleshoot the pump solenoids - make sure the harness is hooked up. More fuel, assuming it's a malfunctioning pump circuit, will make it worse.
Drifting
Joined: Nov 1999
Posts: 1,801
Likes: 2
From: St. Paul MN
Is it popping out through the exhaust? If you have a leak somewhere in the exhaust system that will cause it to do this also. When my exhaust gets loose from the header collectors it'll pop when I lift sometimes. Then I just tighten the three bolts back up and no pop. It's worth a check since you've done exhaust work.
Le Mans Master
Joined: Sep 2000
Posts: 6,303
Likes: 714
From: Bartlett IL
The popping is caused by too much fuel in the exhaust. Adding more will make it worse. I have MagnaFlow on my 84 and get popping as well. Are the injectors larger than the stock ones? If so, the calibration needs to be modified otherwise the ECM is holding the injectors open longer than needed because it "thinks" injectors are smaller. One of the main culprits of decel popping also turns out to be a sticky TPS. Make sure that ECM sees TPS as closed throttle when in decel.
