Backfiring, stalling - 1985 Pontiac Bonneville

make, model, year? backfires are spontaneous burning (exploding) of unburnt fuel outside of the combustion chamber. suspect bad spark plug/s, ignition coils, ignition timing, computer, leaking fuel injector, etc. scan for trouble codes, then post back. because the problem is intermittent, problem manifests only when hot (engine at operating temperature) do tests for both cold & hot conditions. test resistances (ohm) of suspected sensors: cam & crankshaft position sensors, ignition coils (if possible),(search the web for the recommended procedures). also test voltages at the computer (search the web for the pin outs of the computer of your car). also check associated relays (like for the fuel pump, etc.) a bad relay may have its coil open when heated, then becomes good again when cold. i suspect the car may have a good fuel delivery but the sparks are not coming in on demand, thus backfiring.

backfiring is ignition of the fuel mixture while an inlet valve is still open. Check firing order as there may be a HT lead crossed . If it backfires then the mixture is burnt in the inlet manifold so there is nothing left for the cylinders so it will stall. If you are running holley carby then check the power valve for a hole in the diaphram Check for vacuum leaks. check ignition timing is correct and not too far advanced. if the HT leads are touching each other this will induce a spark in the wrong cylinder --use lead spacers from an auto spares shop

if your backfiring I would start at timing and or ignition problems, when it backfires air is pushed back out intake.

Engine system needs inspection on case of backfire:-----

Check out related help links to troubleshoot the vehicle backfire issues:-----

Feels like backfire from engine when decelerating?

http://schematicsdiagram.blogspot.in/2012/02/feels-like-backfire-from-engine-when.html

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Jeep Backfires?

http://technoanswers.blogspot.in/2012/02/jeep-backfires.html

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Nissan Pathfinder stalls and bucks on Acceleration?

http://technoanswers.blogspot.in/2012/02/nissan-pathfinder-stalls-and-bucks-on.html

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Nissan Pathfinder Backfires?

http://technoanswers.blogspot.in/2012/02/nissan-pathfinder-backfires.html
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These will help.
Thanks.

For Nissan pathfinder backfire problem.Click the link below and go through troubleshooting procedure and possibilities:----
Click both the link one by one:----Nissan Pathfinder Backfires?http://technoanswers.blogspot.in/2012/02/nissan-pathfinder-backfires.html
------------Nissan Pathfinder stalls and bucks on Acceleration?http://technoanswers.blogspot.in/2012/02/nissan-pathfinder-stalls-and-bucks-on.html-----------This will help.Thanks.

Backfiring indicates a timing issue. If you have your wires on correctly, your timing chain has stretched and jumped.

I would suspect a burnt valve. An engine compression test will verify this.

check your timing

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