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Discussion Starter #1
I've asked this question before but never was able to fix my erratic idle on my 78. The car seems to have a slight miss, light popping from the exhaust at idle. It smoothes out after 1100 rpm. The whole car shakes at idle, in neutral and in drive.
*I've checked my timing. OK
*Replaced spark plugs, wires, cap, rotor. no change.
*Had carburetor re-built, new gasket, new fuel filter. no change.
I've inspected all of the hoses for leaks but have not done any testing with propane or carb cleaner.
Will a small vacuum leak cause a rough idle? I was told by some old timers that a small leak will not effect it?
Do I need to look at the EGR?
Timing chain has crossed my mind?
Can someone give me some pointers? Thanks.
 

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I've asked this question before but never was able to fix my erratic idle on my 78. The car seems to have a slight miss, light popping from the exhaust at idle. It smoothes out after 1100 rpm. The whole car shakes at idle, in neutral and in drive.
*I've checked my timing. OK
*Replaced spark plugs, wires, cap, rotor. no change.
*Had carburetor re-built, new gasket, new fuel filter. no change.
I've inspected all of the hoses for leaks but have not done any testing with propane or carb cleaner.
Will a small vacuum leak cause a rough idle? I was told by some old timers that a small leak will not effect it?
Do I need to look at the EGR?
Timing chain has crossed my mind?
Can someone give me some pointers? Thanks.
Did you :

Test the coil

Bad valve or valve guide possible

These are two things I've discovered on other peoples cars

then I repaired them and the miss went away:nuts:
 

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compression test will tell you a lot!! also a undamped vacuum gauge,check on net for how to use vacuum gauge.18 inches vacuum at idle with a stock cam,steady needle. any fluctutions of needle could mean an eratic vacuum problem.
my 2 cents worth , good luck:thumbsup::D
 

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check vacumn needle should be steady, if it fluxuates it coild be a valve or valve related , lifter rocker push rod or justnnadjustment, ccheck compresion thisnwill locatenthencylindernwith the problem possible cam lobe worn
 

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arcing between plug leads perhaps, pop the hood at night and check for a light show

A compression check is def. wurth cosidering to rule out burnt out exhaust valve etc.


Have you done anything to the engine recently mods etc?
 

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Discussion Starter #7
I haven't done any mechanical mods to the car since I inherited it. The one thing I did do is disconnect the vacuum to the stove pipe manifold valve on the passenger side. The valve was making a clanking noise and sounded like crap.
From my understanding it is normally open? Am I wrong, Is it normally closed and needs vacuum to open? I don't believe it ran any different after I did this. I only drive the car in the summer so I figured I didn't need it.
 
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