ok guys and gals
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Junior User
Joined: Mar 2004
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ok guys and gals
i have 400m in a 77 i know nothing about the motor other than it has very old 4bbrl carter carb on it.when it is at an idal it sounds really good no misses no stumbling but when it gets warmed up and going down the road it misses and stumbles.and i rebuilt the crb i have looked at the plugs all are pertty good.no fauling .so i'm at a loss what to do next.i was thinking about it having weak comperation but i don't know of any thing else. HELP please before i pull the rest of my hair out
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Joined: Aug 2000
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Sounds like vacuum leaks to me. Possibly the diaphragm in the vacuum advance unit for the distributor is dry rotted and as the throttle is opened and the diaphragm gets the vacuum source then the leak occurs.
Good luck,
Mark
Good luck,
Mark
Laughing Gas
Joined: Feb 2004
Posts: 974
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From: FLA
Originally Posted by frdhighboy77
i have 400m in a 77 i know nothing about the motor other than it has very old 4bbrl carter carb on it.when it is at an idal it sounds really good no misses no stumbling but when it gets warmed up and going down the road it misses and stumbles.and i rebuilt the crb i have looked at the plugs all are pertty good.no fauling .so i'm at a loss what to do next.i was thinking about it having weak comperation but i don't know of any thing else. HELP please before i pull the rest of my hair out
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Joined: Feb 2004
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From: PA
Does it miss and stumble warm at idle or giving it a little gas when in park? Do you have old plug wires? Old plug wires are great for a miss under load. Is the dist cap in good shape? Vacuum leaks are easy to find with a spray bottle and a little water. Carb cleaner works well also just don't spray it around the dist. Check for moisture in and around electronic ignition parts and clean dirty contacts, i've had a few of those. A carb fault won't give you a regular misfire but it will give you a regular chugging. Don't forget to check fuel pressure like purplewg suggested
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Junior User
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ok well
i'll try that today i got some carb cleaner so i'll give every thing a little and see what happens.
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Laughing Gas
Joined: Feb 2004
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From: FLA
Originally Posted by Ironeagle
Does it miss and stumble warm at idle or giving it a little gas when in park? Do you have old plug wires? Old plug wires are great for a miss under load. Is the dist cap in good shape? Vacuum leaks are easy to find with a spray bottle and a little water. Carb cleaner works well also just don't spray it around the dist. Check for moisture in and around electronic ignition parts and clean dirty contacts, i've had a few of those. A carb fault won't give you a regular misfire but it will give you a regular chugging. Don't forget to check fuel pressure like purplewg suggested
Don't you just love it when you never hear what the fix was.
