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Old 05-06-2003, 10:24 PM   #1
mcfly5
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Default need some help with my '79 L82....runs rough

i know...."runs rough" could be lots of things....but i've replaced the following: plugs, wires, rotor, cap, pcv, fuel filter, rear seal, air filter. firing order is correct, vacuum lines are correct. all the emissions stuff has been removed. the car ran great, so i've never touched any of the carb settings. i start it, it never really idles well. it just kind of lopes; everything is stock. any ideas?
help!! the weather is getting nice!!
thanks
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Old 05-06-2003, 10:30 PM   #2
dman535
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Default Re: need some help with my '79 L82....runs rough (mcfly5)

where is your timing ? You try advancing it ?
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Old 05-06-2003, 10:30 PM   #3
Jvette73
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Default Re: need some help with my '79 L82....runs rough (mcfly5)

Have you done a compression check? This would tel you the general condition of the engine mechanical. For instance you may have a burnt exhaust valve or blown head gasket between two cylinders. These failures would show up in a compression test.
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Old 05-06-2003, 10:30 PM   #4
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Default Re: need some help with my '79 L82....runs rough (mcfly5)

Have you checked the idle mixture? You said the vacuum hoses are fine, but what is the reading? Is your air filter on tight?

What's your timing at? Have you checked this? Your initial should be at 10-12 BTDC w/o the vacuum advance.

Do you have the stock cam? If you have a heavy aftermarket cam, you would naturally have a "lopey" idle. Different from a rough idle.

Just a few suggestions.

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Old 05-06-2003, 10:39 PM   #5
Jvette73
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Default Re: need some help with my '79 L82....runs rough (Jvette73)

Also could be worn timing chain stretched , or jumped a tooth causing late valve timing and low compression. How many miles on the engine?
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Old 05-07-2003, 05:58 AM   #6
paul 74
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Default Re: need some help with my '79 L82....runs rough (mcfly5)

If it lopes at idle but doesn't stall, then that is simply the L-82 cam at work.
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Old 05-07-2003, 08:55 AM   #7
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Default Re: need some help with my '79 L82....runs rough (mcfly5)

Mine's lopey at idle, too. The L82 cam has a lot to do with it, but there could also be a vacuum leak -- carb base or intake manifold gasket are two suspects.

I got this tech tip last night: Spray carb cleaner slowly around the areas you want to test. If the engine increases in rpm as you spray a certain area, you've found a vacuum leak. :yesnod:
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Old 05-07-2003, 12:08 PM   #8
groovyjay
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Default Re: need some help with my '79 L82....runs rough (mcfly5)

Have you checked the vacuum lines? :cheers:
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Old 05-07-2003, 12:22 PM   #9
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Default Re: need some help with my '79 L82....runs rough (groovyjay)

Does it run Ok when it is cold, then gets worse as the enigine reaches full temp? It so this is also a sign that the HEI module is bad. Usually they do not show stumble/hesitation until the throttle begins to open (can't fire the richer mixture).
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Old 05-07-2003, 04:40 PM   #10
john's '81 mouse
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Default Re: need some help with my '79 L82....runs rough (DaveL82)

Quote: "Does it run Ok when it is cold, then gets worse as the enigine reaches full temp? It so this is also a sign that the HEI module is bad. Usually they do not show stumble/hesitation until the throttle begins to open (can't fire the richer mixture)."

Sorry, but I've got to take exception to what you're saying........the 'mixture' is richer when the engine is cold, and then leans out as the choke comes off as the engine warms up. Believe malfunction of ignition model is more often due to presence of heat.........as the model becomes hotter, it begins to malfunction, much like a bad coil will do. Having said that, I belive this particular problem is more likely attributable to an air/fuel/vacuum problem, or engine timing is too slow (not advanced far enough) for some reason .
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Old 05-07-2003, 05:50 PM   #11
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Default Re: need some help with my '79 L82....runs rough (mcfly5)

If you've hooked up a vacume gauge to it it should draw about 19 inches of vacume. I'd say if it ran good before and the lopy idle is a new condition it somewhere in you carb. The L-82 is a little rougher than the L-48? Put everything back to stock settings and see if it dosent clear up, if not look at your carb for the problem. :bb
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Old 05-07-2003, 06:51 PM   #12
DaveL82
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Default Re: need some help with my '79 L82....runs rough (killain)

Johns 81 - you take take exception with no problem and this may not be the cause. I've had 6 fail over the last 20 years. The engine runs fine cold, the the module gets hot, this then causes the car to bog/run rough when you put your foot on the gas (richer mixture). Idle and part throttle crusie are usually fine when the module fails. However this could be an exception to the normal failure mode and may be worth a try.
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Old 05-09-2003, 05:48 AM   #13
jubee
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Default Re: need some help with my '79 L82....runs rough (mcfly5)

I've been having the same problem. Do a search under my user id and see the posts I've been chasing. I still ahven't figured mine out. I'm doing another compresion check tomorrow just to be safe.

Joe
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Old 05-09-2003, 08:12 AM   #14
Rich80
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Default Re: need some help with my '79 L82....runs rough (mcfly5)

Mine lopes when i first start it up. Always did that. I know its a vacuum leak somewhere. Once it warms up shes fine.... :smash:
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Old 05-09-2003, 08:12 AM
 
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