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Old 01-03-2012, 07:25 PM
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ignition problems

Ok, here's my problem. Around 1,000 rpm my ignition goes nuts, sometimes it bounces all over, sometimes the car will not rev any higher, and sometimes its fine. I also have a bouncing tach at other rpm but the car will run without a hiccup at higher rpm even with a bouncing tach.

My first thought is ignition module (its a gm hei conversion with a cheap autozone module). HOWEVER, another problem is that sometimes it will stick at 1400rpm when I let my foot off the gas and after a few seconds go back down to idle. This makes me think its a vacuum leak, but that doesn't explain the bouncing tach.

Thoughts?

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Old 01-03-2012, 10:12 PM
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Even so I don't remember all the details of it as its been many years ago a used to be friend of mine had a issue like this and it turned out to be a bad ground. This info may not help at all but any info is a starting point.
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Old 01-04-2012, 05:55 AM
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What is the car/engine AP?

Is it a factory tach or an aftermarket tach?
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Old 01-04-2012, 06:26 AM
How fast is fast enough?
 
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78 datsun 280z with megasquirt and factory tach. The problem started 2 days ago, worked fine until 2 days ago. I don't think its the tach as the engine is acting up, it could be a bad ground I suppose, I'll try to check the grounds.
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Old 01-04-2012, 06:52 AM
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280Z with the original engine or a transplant?
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Old 01-04-2012, 07:28 AM
How fast is fast enough?
 
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original engine, l28e, switched to a gm hei module, it was running fine but had a slight tach bounce, so I switched the module under warrenty and now its acting like this. I would guess I got another bad module but that wouldn't explain why it hangs up at 1400rpm on the way back to idle.
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Old 01-04-2012, 07:46 AM
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What sort of shape was the distributor in before the conversion? How are the bushings, advance weights (if it has any) etc.

Have you checked the IAC? Maybe clogged or sticking.

Does your mega-squirt also control timing or just the injectors?
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Old 01-04-2012, 08:08 AM
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no iac valve, the distributor its old but never have me issue, new cap and rotor, mechanical and vacuum advance built into the distributor.
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Old 01-04-2012, 09:03 AM
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my 2 cents on the ign

try these things - disconnect the tack- re run - any change?? next = remoce dist cap- look very close as to the carbon center? is that round & perfect? no small missing areas? also carbon tracks in cap? how long since replaced? cap & rotor? also - maybe a loose wire on coil or coil spark tracking? test it @ night in dark - watch all ignition areas- plugs , wires, cap , coils areas?? Happy times are ahead!!
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