How do Iset my timing on my Jeep? - JeepForum.com

 
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post #1 of 7 Old 08-31-2007, 02:36 PM Thread Starter
02Lightning
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How do Iset my timing on my Jeep?

I know how to set it but is there something you disconnect to set base timing?


1995 Jeep Grand Cherokee Limited 4.0L NP249 Transfer Case, 42RE, 212,000 miles
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post #2 of 7 Old 08-31-2007, 03:27 PM
rm2001wj
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I'm pretty sure that the "base" timing is programmed into the PCM and there is nothing much you can do about it. The PCM adjusts the timing, as needed, based on various sensor inputs and its programming. Timing adjustments different from those produced by the PCM can be made by intercepting the CPS signals, making changes, and then sending them on to the PCM. Also it's possible to intercept the PCM signal going to the coil and then add a delay.

What are you thinking about doing?

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post #3 of 7 Old 09-01-2007, 04:32 PM Thread Starter
02Lightning
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Make sure my base timing is set. I know on a 88 mustang I use to have you would pull a plug to get base timing. I know on early 90's GM cars you had to jump a plug under the dash. I want to put a timing light on my jeep and see where base timing is and adjust it if needed. I'm about 95% sure you can change your base timing on a jeep. All you have to do is move the distributor, I just want to be sure I'm looking at base timing with no advance and I need to know how to eliminate the advance before I mess with it.

1995 Jeep Grand Cherokee Limited 4.0L NP249 Transfer Case, 42RE, 212,000 miles
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post #4 of 7 Old 09-01-2007, 04:43 PM
UltimatE
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Putting a timing light on your engine will tell you where your timing stands as it is right now. Compare that to what the manual says should be the correct timing for your engine.

-Matt

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post #5 of 7 Old 09-01-2007, 05:40 PM
rm2001wj
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The camshaft position sensor is in the distributor and its signal is used for timing the injector pulses. If you try to move the distributor from its factory position the injector timing gets messed up. Also, the cam position sensor is used to tell the PCM which cylinder is #1. As I mentioned earlier, the crankshaft position sensor is used for ignition timing. It's possible to ream out the bolts holes and move it a little for a minor timing adjustment. Usually the CPS is so hard to get to that hardly anyone would try that.

Still, let us know if you have any success.
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post #6 of 7 Old 09-01-2007, 07:33 PM Thread Starter
02Lightning
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Quote:
Originally Posted by rm2001wj
The camshaft position sensor is in the distributor and its signal is used for timing the injector pulses. If you try to move the distributor from its factory position the injector timing gets messed up. Also, the cam position sensor is used to tell the PCM which cylinder is #1. As I mentioned earlier, the crankshaft position sensor is used for ignition timing. It's possible to ream out the bolts holes and move it a little for a minor timing adjustment. Usually the CPS is so hard to get to that hardly anyone would try that.

Still, let us know if you have any success.
Maybe I stand corrected, sounds like I can't move the distributor like old school cars then?

1995 Jeep Grand Cherokee Limited 4.0L NP249 Transfer Case, 42RE, 212,000 miles
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post #7 of 7 Old 09-01-2007, 07:35 PM
greasefingers
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Correct the distributor does not rotate

Cheers Steve

94 Black Laredo 4-Liter with QuadraTrac (42RE trans & NP249 TC) 200,000 + miles purchased new

88 Cherokee 2-door with 5speed manual 139K miles(deceased) purchased new
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