Backfire
#1
06-23-2018, 12:07 PM
Backfire
I have a 460 in my 1984 RV. My coil wire came off while driving. As I pulled over the engine backfired. I replaced the wire and ever since while decelerating from highway speed it backfires loudly. The engine runs great and had never backfired before. Various mechanics have looked at it and can't find the problem. Any ideas?
#2
06-23-2018, 02:24 PM
Can you tell us what kind of emission stuff is on the engine if any?
Will have to go back and check to see if there are anti backfire valves that are on it and if so could they be rusted beyond doing their job. Are the AIR pumps still on it?
Will have to go back and check to see if there are anti backfire valves that are on it and if so could they be rusted beyond doing their job. Are the AIR pumps still on it?
#6
06-25-2018, 05:03 AM
Backfires can have a few causes, some of which are,
mixture too lean resulting in misfire and unburned fuel getting ignited in the exhaust
mixture too rich and addl fuel igniting in the exhaust
leaking exhaust manifold pulling in excess air
If air pumps are on engine bypass valve may not be directing excess air on deceleration to air cleaner instead is directing it to exhaust manifold.
intermittent ignition
ignition timing incorrect resulting in backfire
What is the condition of the dist and cap and rotor?
It could be coincidence that backfire started at the time coil wire came off but timing chain problem might be involved.
Ign module might have suffered from initial backfire
mixture too lean resulting in misfire and unburned fuel getting ignited in the exhaust
mixture too rich and addl fuel igniting in the exhaust
leaking exhaust manifold pulling in excess air
If air pumps are on engine bypass valve may not be directing excess air on deceleration to air cleaner instead is directing it to exhaust manifold.
intermittent ignition
ignition timing incorrect resulting in backfire
What is the condition of the dist and cap and rotor?
It could be coincidence that backfire started at the time coil wire came off but timing chain problem might be involved.
Ign module might have suffered from initial backfire
#8
06-26-2018, 06:49 AM
I have a couple of pennies to throw around, so here's my .02 worth...
Is it backfiring thru the intake or the exhaust. Since it was running fine until the coil wire came off, I would check for a loose or cracked vacuum line. As Hanky mentioned, a lean condition can cause backfire.
Is it backfiring thru the intake or the exhaust. Since it was running fine until the coil wire came off, I would check for a loose or cracked vacuum line. As Hanky mentioned, a lean condition can cause backfire.
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