backfiring problem, loss of power.
Printed From: CorrectCraftFan.com
Category: Repairs and Maintenance
Forum Name: Engine Repair
Forum Discription: Engine problems and solutions
URL: http://www.CorrectCraftFan.com/forum/forum_posts.asp?TID=3382
Printed Date: November-23-2024 at 9:25am
Topic: backfiring problem, loss of power.
Posted By: chavonbravo
Subject: backfiring problem, loss of power.
Date Posted: April-17-2006 at 1:25pm
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All of a sudden, my engine started backfiring out of nowhere. I left it on idle for about 10 minutes, then when accelerating, it would backfire. It was only noticeable when accelerating and putting strain on the motor by accelerating in gear. In neutral, wasn't noticeable, though may have been there. Later, even on idle, it would knock a little, well, not knock, but you know, like one of the cylinders was misfiring occasionaly. I narrowed it down to the one cylinder it occurs on. When disconnecting the spark plug cable on that cylinder, it idles great, none of that sputtering, misfiring. Changed all spark plugs and spark plug cable while I was at it, nothing. Next on the list, I'm about to put a new distributor cap/rotor on. What do you guys think this could be? And hopefully not expensive to fix?
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Replies:
Posted By: 79nautique
Date Posted: April-17-2006 at 2:16pm
double check your firing order?
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http://www.correctcraftfan.com/diaries/details.asp?ID=756&sort=&pagenum=1&yrstart=1979&yrend=1979 - 79 nautique
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Posted By: GottaSki
Date Posted: April-17-2006 at 5:41pm
I suspect a broken distributer advance spring.
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"There is nothing, absolutely nothing, half so much worthwhile as messing around with boats...simply messing."
River Rat to Mole
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Posted By: JEFF KOSTIS
Date Posted: April-17-2006 at 9:09pm
Did it happen all of a sudden or after some work was done on it?? Funny it happened all of a sudden. Only thing that comes to mind is see if you got some condensation in the cap causing it to track. Happens to ours on certain days and even my neighbors Centurion. Its occurrs most just after warmup of an idling engine or running for 5 minutes, shutting it down for 5 minutes, then restarting. Good luck!!
Jeff...
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MUSTANG COUNTRY
http://www.correctcraftfan.com/diaries/details.asp?ID=1074 - 1974 Mustang 17
http://www.correctcraftfan.com/diaries/details.asp?ID=1093 - 1976 Mustang 17
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Posted By: David F
Date Posted: April-18-2006 at 10:52am
Let's think about things that cause backfiring through the carburetor. Basically, it is the fuel igniting when the intake vavle is open. So, my thoughts...
1. Spark plug is firing before the intake vavle closes. Causes: bad spark plug wires causing cross fire. Bad distributor cap/rotor. Wildly incorrect timing...did you recently adjust timing and forget to tighten retaining bolt?
2. Timing chain has jump a tooth or more.
3. Intake vavle is burned and not sealing upon closing.
4. Intake valve spring is broken. Would likely hear racket.
Since you said you narrowed it down to one cylinder, to me this takes timing out of the equation.
Let us know what you find...might consider doing a compression check on the suspect cylinder.
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Posted By: chavonbravo
Date Posted: April-21-2006 at 10:17pm
Was the cap. Soon as I took it off and looked on the inside, I noticed that one of the metal leads was burnt pretty bad. Sure enough, upon changing, all was good. She started right up after that, with no problems at all. Haven't tried it on the lake yet though, which will be the real test. Sometimes before, when it wouldn't start, I'd leave it at wot and open up one of the butterflys all the way, like when it's choked, to get it to start. Hopefully won't have to do that anymore, as it's embarassing on the dock to open up the engine and take off the air filter and do all that stuff just to start the engine.
Oh, one more thing. Reading around, I've seen that backfiring can mess up your power valves on the Holley's. How to tell if they're bad or not?
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