1st Generation Specific (1979-1985) 1979-1985 Discussion including performance modifications and technical support sections

Timing jitter, or is it a misfire?

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Old 05-13-09, 05:53 PM
  #26  
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Yep.

I never did get rid of it, and doesn't seem to interfere with the engine running well - it's slight when the engine is warm.

It makes for some interesting subsonics when the car is warming up on the choke (travels right thru the walls of the house) but otherwise doesn't seem to have any impact.

My current working theory is that the distributor gears have enough mecahincal wear on them that they're allowing a bit of slap at low RPMs, which wobbles the timing slightly. I can find no spec anywhere for dizzy gear wear limits, though.
Old 05-13-09, 09:54 PM
  #27  
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Originally Posted by vxturboxv
Also a trick you can do is to unhook or temporarily plug your smog pump so it’s not cooling your cats. .Then retard your IGN timing 5-10*. This will add a ton of heat to the exhaust. Drive it like a baby to the test. And once passed make sure to change settings back to normal. My car passed years ago by doing this.
air pump actually adds heat to the cats. it speeds up the reaction. retarding the timing does work, but ive never needed
Old 05-13-09, 09:58 PM
  #28  
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Originally Posted by DivinDriver
Yep.

I never did get rid of it, and doesn't seem to interfere with the engine running well - it's slight when the engine is warm.

It makes for some interesting subsonics when the car is warming up on the choke (travels right thru the walls of the house) but otherwise doesn't seem to have any impact.

My current working theory is that the distributor gears have enough mecahincal wear on them that they're allowing a bit of slap at low RPMs, which wobbles the timing slightly. I can find no spec anywhere for dizzy gear wear limits, though.
i notice my current FC does this a little too, at idle its like 1 degree, which is close enough, if the rotor is only moving 1/3 crank speed, how much is 1 degree really?
Old 05-13-09, 11:37 PM
  #29  
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I've seen jitter. I think it was caused by the pickup itself. It's not the reluctor because I didn't see it occur on the other pickup, and it's not the ignitor because I swapped them and still saw jitter on just that one pickup.

Maybe the pickup's self-centering effect was not working very well? Maybe it was seeing the edges of the reluctor differently ie reading the leading edge of one while reading the trailing edge of the next, and so on.
Old 05-14-09, 03:44 AM
  #30  
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Mine does exactly the same thing. Never found a way around it, or any issues with my ignition system.

btw, the stock pulley has a circumference of 360 millimeters, so one degree would be one millimeter.

Glad to hear that you passed okay...
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