Help with performance problem, please.
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Fleet Mechanic
Joined: Apr 2004
Posts: 1,443
Likes: 5
From: Willamette Valley, Oregon
Help with performance problem, please.
73' 302, C4, about a year ago it got fresh heads and pistons, new 2bbl holly, electronic ign conversion (drop in unit, into old dizzy) Plugs and wires...
Electric fan about a month ago...
Ran well for about a year. Now it idles very poorly (never had a great idle, but now its very poor)
When I take off it cuts out pretty badly for quite a while, at higher rpm its stronger, but seems to be still missing.
When I thumb the throttle it responds great, but in normal driving pretty badly.
I have looked for vac leaks, looked and listened so far.
Cleaned the cap and rotor.
Checked a plug, nice grey ash, pretty clean, bit pink on the cone.
Double checked fuel flow (filters full)
Turned up the idle mixture to see the reaction; stronger at idle, still missing bad..
Can an alternator (with the stress of the new electric fan) begin to seaze up and still show a strong charging on the gauge?
Pertronix unit, can it fail and still run, just poorly?
ANY and ALL ideas appreciated, Im lost...
Electric fan about a month ago...
Ran well for about a year. Now it idles very poorly (never had a great idle, but now its very poor)
When I take off it cuts out pretty badly for quite a while, at higher rpm its stronger, but seems to be still missing.
When I thumb the throttle it responds great, but in normal driving pretty badly.
I have looked for vac leaks, looked and listened so far.
Cleaned the cap and rotor.
Checked a plug, nice grey ash, pretty clean, bit pink on the cone.
Double checked fuel flow (filters full)
Turned up the idle mixture to see the reaction; stronger at idle, still missing bad..
Can an alternator (with the stress of the new electric fan) begin to seaze up and still show a strong charging on the gauge?
Pertronix unit, can it fail and still run, just poorly?
ANY and ALL ideas appreciated, Im lost...
Hotshot
Joined: Jul 2002
Posts: 14,285
Likes: 12
From: Bend,OR
first would be a tune up. new plugs,cap/rotor and possibly wires if they are old. check your timing it should be 8*-10* btdc. you might also do a compression test as well .
to check for vacum leaks spray carb cleaner around the intake etc.. if the idle increases then you have a leak. might even replace the fuel filter
to check for vacum leaks spray carb cleaner around the intake etc.. if the idle increases then you have a leak. might even replace the fuel filter
Senior User
Joined: Aug 2005
Posts: 387
Likes: 0
Originally Posted by Kemicalburns
first would be a tune up. new plugs,cap/rotor and possibly wires if they are old. check your timing it should be 8*-10* btdc. you might also do a compression test as well .
to check for vacum leaks spray carb cleaner around the intake etc.. if the idle increases then you have a leak. might even replace the fuel filter
to check for vacum leaks spray carb cleaner around the intake etc.. if the idle increases then you have a leak. might even replace the fuel filter
Elder User
Joined: Oct 2004
Posts: 541
Likes: 0
From: Fleming Ga
Try isolating the miss to determine what cylinder it is. Pull the plug wires off one at a time to determine which cylinder is missing. It the miss seems to be moving around to different cylinders or just a partial miss on more than one cylinder then it's probably a vacumn leak/carb problem. Otherwise check compression, wires, plugs on the missing cylinder. If it has egr make sure the egr isn't sticking open. Check timing with a light and make sure vacumn and mechanical advance is working correctly.
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