post #1 of Old 04-05-2002, 07:05 PM Thread Starter
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How does the comupter on 4.2 controll timing

just wondering how the computer on a 258 controlls the ignition timing...

1988 yj, computer bypass, webber carb and the ever famous BA10/5 transmission (if you have one you know it or will find out).
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post #2 of Old 04-26-2002, 06:39 PM
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The 258 has vacuum advance timing so the engine Rpm decifers the advance
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post #3 of Old 04-26-2002, 06:47 PM
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That is a bit of a mystery subject, but one way is by the computer taking an input from the knock sensor mounted on the intake manifold. If the computer senses any pinging, it will retard the timing. There are probably other factors, also, but I haven't been able to find them.

Currently an '86 CJ-7 and a '77 CJ-7 Golden Eagle---#4 and 5 following a '01 Sahara, '90 Sahara, and '85 CJ-7....
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