Ignition module and crazy tach!!!! - Pontiac GTO Forum
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post #1 of 5 (permalink) Old 08-09-2013, 01:29 AM Thread Starter
 
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Ignition module and crazy tach!!!!

hi fellas. SO my ignition module went out on my Mallory unilite which I hear I better get use to. so I replaced it and it started fine but after 10 secs my tach starts going crazy and engine starts running rough. It happens every time I turn it off and restart it. I am assuming my timing or vacuum are off now. my question is, how can this happen if distributor didn't move. can it be something else I am missing? and if indeed it is my timing and vacuum how can replacing a module throw it off?
thanks in advance

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post #2 of 5 (permalink) Old 08-09-2013, 11:06 AM
 
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uni-fat free

I too have A Mallory Unilite module assembly on my 455. Did some reading awhile back and discovered that these things want only a few volts going to them, otherwise they burn right up. I've not had any issues so far with mine, but am going to delve into this matter further as I'm running the resistor wire up to a ballast resistor. And the voltage is considerably low (under 6 volts), but seems to pop right off everytime and run great. (Read one article that stated his ran 15 years without any module changeout, with less than 6v going to the coil!).
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post #3 of 5 (permalink) Old 08-09-2013, 12:31 PM Thread Starter
 
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I hope so. I actually got lucky and wad already in the car when I bought it. Only part I kept from the engine. So maybe it was time for a new module. I just don't understand how replacing the module can throw off my timing. That if it is my timing? I'm not sure if it can be an electrical problem if the last one was fine. I even tried a new coil and it still seemed off.

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post #4 of 5 (permalink) Old 08-10-2013, 01:20 AM Thread Starter
 
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well my engine seems to be running fine now. my tach is still going crazy and the car will die when I turn on my lights or give it some gas when its in drive. so now im thinking its gotta be a bad ground somewhere. Or can a ballast resistor cause this?
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post #5 of 5 (permalink) Old 08-10-2013, 02:36 AM
 
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resistifier

As others have stated, Pontiac ran only the resistor wire- no ballast. However, these Mallory seem to want the ballast, also. If you do have the ballast, what voltage are you seeing at the coil + when the key is on, engine not running, then with it running? If it's 9v or more, then something's wrong. I think if it's more than 6v with these Mallory, it's still too high, but don't quote me on that yet, as I also will check to verify soon, unless someone with knowledge of these would care to chime in. Yes, it does seem like maybe you have a possible bad ground somewhere. I would check them all. Check for bad/shorted wiring also. You might want to check your voltage regulator & alternator, if you haven't done so already. A bad ballast resistor can cause all sorts of nasty things to happen. (These symptoms included, maybe not so much the headlight thing, though, but possible). You can take an ohm reading on the ballast (with wires disconnected) and compare it with Mallory specs for your unit (get the module #). I just haven't made that a priority yet on my list.
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