Loss of power and backfiring - Off-Road Forums & Discussion Groups
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post #1 of (permalink) Old 02-10-2000, 04:36 PM
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Loss of power and backfiring

I have an 86 Bronco that occasionally loses power and backfires when the engine is warm an the gas tank is less than 1/2 full. Any ideas on what needs fixing?

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post #2 of (permalink) Old 02-10-2000, 05:03 PM
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Re: Loss of power and backfiring

Need more info. Tell us what engine you have, and whether its carburator or Fuel Injected.

post #3 of (permalink) Old 02-11-2000, 10:22 AM
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Re: Loss of power and backfiring

It is a 302 with EFI.

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post #4 of (permalink) Old 02-13-2000, 01:10 AM
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Re: Loss of power and backfiring

Well, backfire is a funny word, 'cuz it means different things to diff. people. To some it means "out the back" (exhaust). To some it means "backwards" (towards the front - out the intake).

If your Bronc is backfiring in the exhaust system, (barring major mech. problems, unlikely in your case 'cuz it runs ok some of the time), its usually caused by ignition problem. Intermittent ignition problems let mixture pass through cylinder (without combustion), and out to exhaust where it gets lit up by heat of exhaust manifold or system.

On the other hand, backfiring out the intake (here again, barring major mech. problems like jumped cam timing, etc., unlikely for same reason as above), is usually caused by a too-lean mixture. Was common in carb vehicles, a lot less so with FI. Low fuel pressure in the fuel rail due to weak fuel pump, regulator problems, tank venting problems, etc. are a possibility.

So which direction is your backfire? Need to be sure - can really chase your tail if you think its one, but its really the other!

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