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Discussion Starter · #1 ·
my '78 w/turbo motor has a miss that goes away as rpm's rise. the distributor has been "welded" to suit the Accel DFI. it also has a HI-6 Crane ignition with a mallory coil. Everything is new( motor,DFI, ignition, fuel system, etc) except the distributor, whichhas been swapped with 3 other units. What could be causing the miss??
 

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Discussion Starter · #2 ·
<b>Plug wires, maybe</b>

Just last week, we replaced the plugs on a '83ZXT that had a miss. As soon as the new wires were on, the miss was gone.

Just a suggestion.

Chris Behney
Redline Autosports
 

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Discussion Starter · #3 ·
<b>RE: Plug wires, maybe</b>

Chris did you replace the plugs and wires or just the wires? Mine has a new set of NGK wires with no difference. The plugs have a little over 3500 miles.
 

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Discussion Starter · #4 ·
<b>What shows on a scope?</b>

Tim,

What shows up when you connect the engine on a scope? Is it the same cylinder that is missing? or does the "miss" move about the cylinders.... from one to another.....
 

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Too much advance?

Tim,
If you have your initial timing set real aggressive the car will lope at idle (about 800 RPM) similar to a miss and will smooth out by the time you get to 1200 - 1500 RPM. I have the distributor timing on my '77 NA "firewalled" as far clockwise as it can go and get a rough idle, more difficult starting but great MPG and strong lower end.
Phantom
 

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Discussion Starter · #6 ·
<b>RE: What shows on a scope?</b>

Dennis , what do you mean by a "scope"? Is it one of those engine analyzers the inspection stations have?
 

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Discussion Starter · #7 ·
<b>RE: Too much advance?</b>

Phantom, Alamo has the car and they think the miss is only on one cylinder, which to me says its a stuck valve. I don't know if they have put a vacuum guage on it yet or done a compression check. Steve has been concentrating on ignition timing.
 

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What is a scope...

Hi Tim,

Thats right.... go to any tune-up place.... including some of the finer private garages and you will see an upright with what looks like a tv picture tube (CRT) on it... typically on the left side or in the center. When its connected they display what is happening in the ignition for each cylinder.

The line that you see going across them is read this way. The first high point is cylinder #1. The second high point, which is lower then the first high point, but higher then the third high point is cylinder number two. Each high point stand for a cylinder. 4 cylinders have 4 high points, 6 cylinders have 6 high points.... etc.

The wave shows, coil build up and release. These are great tools.... but expensive for most people. I haven't seen to many in private garages... But I sure would like to have one in mine.

The older ones have dwell meters on them.... these aren't used very often now adays... all have timing lights, some also have gas anlyzers...

If you hooked up your car to a scope, you would know if the problem is ignition related or not. If you didn't have 6 high points.... that would indicate a problem in one of the ignition circuits. On the other hand... if it did show 6 strong high points... the problem would be else where... like in the valve train. Carbs.... etc.

Good Luck, Sounds like ya have someone looking into it already....

BTW, the reason I know about the older scopes is because I read about it in a book... maybe a couple of years ago when I was in an Auto shop class... or something like that.

Cheers,
Dennis
 
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