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I haven't set my fast idle cam so I have to give it a little throttle for a minute or two and when I put it in gear but it warms up pretty quick byt the time I'm around the first corner in my neighborhood.
I had a backfire once because my distributor gear sheared the shear pin when the oil pump got some carbon in it. I have the worse luck. My mustang did the same thing in 94. Yes, I change the oil and filter every 3000 miles!
I can only guess that your carb or your timing isn't quite right for your backfire problem.
I have some backfire with the 400 in my F250. Does it on deceleration or coasting down a hill. One mechanic told me it was because it has headers and the exhaust manifold gaskets have a couple leaks. Hadn't heard that before and I really don't know if it's true or not. It has had a recent tune up but it is getting close to carb rebuild time.
As far as the sputter/stall on cold starts, I'd be worried if it didn't do that! I converted the auto choke on my current truck to a manual choke and it has minimized the stalling.
Leaking exhaust WILL cause some backfiring sounds when deceleration. I would fix those leaky header/manifold gaskets asap if it is the ones between the headers and the heads. If not, you may burn a valve because you are sucking in cool air when you decel.
If it is backfiring thru the carb, then you eiter have 1) a lean condition( not enough fuel) 2) Slow ignition timing or 3) maybe a weak sparkplug or plugwire that could be arcing.
Just a thought,
Jimmy
Thanks for the advice on the header gaskets. I will get that taken care of. I did have a some backfire through the carb and that was cured by new plugs and wires.
Engines backfire if the carburetors are running too lean (not enough gas), and also if your timing is off. A loose, cracked or leaking vacuum hose will throw your mixture off and make it backfire or "pop". An exhaust leak can, indeed, throw your mixture off, and cause this too.
I just experienced some backfiring while driving in the mountains of VA (Blue Ridge Parkway). I usually drop it down into second (or, depending on conditions, first) going downhill. When I did that, it backfired regularly while in the lower gear (through the exhaust) until I figured out that if I gave it just the slightest bit of throttle it stopped. Strange.
I figured it was just sucking in a little too much gas and blowing it out unburned, collecting in the exhaust and igniting. Is that what happens with an exhaust backfire?
In a related story, I used to work for a moving company outside of DC. One of the drivers used to take great delight in producing backfires out on the beltway. We'd be driving along and about a tenth of a mile or so before an underpass he would shut off the ignition (truck was still in gear). When we got under the bridge he would turn the ignition back on and ...WHOMP... it would backfire. I know for sure he lost at least 2 mufflers doing that. What fun!
Silentheero-
Does your motor have a solid mount fan? If so, grab a blade from each side(carefully) and try to rock it back and forth. If you feel slack before any serious resistance that's your timing chain. The engine will retard itself on deceleration because of the slack and may backfire on heavy (higher rpm) deceleration. Give it a look. GL
Mine backfired a little when i first bought it, 78' f-250 with built four sixty...I found out it was the carb backfiring, not the engine.....Yes if i get on it when its cold, it backfires a little, with a sputter but other than that it runs just as well as my 2000 chev Tahoe................
My 460 Does this whenever i jump on it hard from a dead stop. I looked at my timing and it looks like it is coming in to soon. I am going to address this subject as soon as i get headers on and can tune the system with all the components in place