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MAS1866
User
Jun 28, 2010, 9:07 PM
Post #1 of 4
(2943 views)
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1986 malibu- low power
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I've got this 1986 chev malibu in my shop. the thing seems to have a little bog to it when it is sitting in park and you gun it(especially cold).
On the road(warmed up), it will got through first ok, then in second it will start surging and bucking. If you let off and accelerater ever so slowly, it's ok to about 50-55 mph.
When it shifts into third, it does the bucking think amost all of the time....New fuel filter, air filter, carb, cleaned with spray type carb cleaner.
ANY IDEAS?
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Tom Greenleaf
Ultimate Carjunky
/ Moderator
Jun 28, 2010, 9:14 PM
Post #2 of 4
(2937 views)
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Re: 1986 malibu- low power
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Late carbs were a nightmare. Make sure choke pull off (primary) is set exactly right. I like drill bit measures better than angle tool.
Make sure it electrically shuts off the choke fairly quickly. New or rebuilt carb is just a beginning. They about all needed to be tweaked for the vehicle. Choke is critical as it will change all other behaviours. No harm in checking fuel pressure - guess 4-6 psi and volume into glass jar too.
Which engine and carb?
T
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MAS1866
User
Jul 5, 2010, 1:40 AM
Post #3 of 4
(2918 views)
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Re: 1986 malibu- low power
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The electric choke pull-off is not working, but I don't think that is the problem. I warm the engine up to operating temperature before testing it and the warmth of the engine is enough to open the choke all the way...or would the vacuum of the carb during on-road operation pull the choke closed? this is getting a little deep. the engine leeks oil like a sieve, has blown-by like crazy, so the guy doesn't want to spend too much on it, he just wants it as a back-up vehicle if we can get it running decent. Any hope you think?
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Tom Greenleaf
Ultimate Carjunky
/ Moderator
Jul 5, 2010, 2:31 AM
Post #4 of 4
(2915 views)
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Re: 1986 malibu- low power
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If electric choke heater doesn't work on a new carb then you must mean the car isn't supplying power to it. You can test it with a jumper wire to the battery with a fused jumper wire and watch it open just sitting there stone cold.
Engine heat is NOT enough so it will come back unseen while driving and be part on blowing the fuel mixture - then you stop to take a look and true - the engine heat rises and it may open. Drive along and it partially shuts again.
There isn't much engine heat up high in the carb. Older ones sucked in hot exhaust gasses AND some ran a heater hose right by them as back ups to shut off the chokes. Remember as gasoline evaporates it gets so cold it can frost on the hottest day and carb icing was once a big problem.
Gotta fix that or run a new wire such the it has power and is hot to touch all the time after it has time when warmed up. Changing it to manual is harder to figure than fixing it. Pulling a choke lever will not allow for the screw for fast idle to ride up the step cam so will never work right unless driver always knows to push gas pedal part way while pulling on the choke or get a marine no step cam for cold fast idle.
Again - the easiest thing to do is fix it as intended. Watch it open as mentioned and feel that it get hot. Bet that is 90% of the trouble,
T
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