1987 258ci wont idle - Page 2 - JeepForum.com

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post #16 of 22 Old 05-16-2013, 12:24 AM
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I personally would not pinch the vacuum line with vise grips, cause the teeth can dig in to far an cause another leak. Especially since its so easy to just pull the vac line off the distributor an plug it with a screw or bolt. Also take carb cleaner and mist all vac lines and around the bottom of the carb. If idle picks up you've found your leak. As for your last question and please someone chime in if im missing/wrong but your timing will jump around if theres a vacuum leaks; because the distributor advances or retards depending on the manifold vacuum pressure. So with this in mind when you have a leak it causes rough idle. Which in turn gives you high an low spots in the RPMs and does not give the distributor a constant clean vacuum signal. So the distributor is constantly changing from the constant change in vacuum pressure going up an down with the rough idle.

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post #17 of 22 Old 05-16-2013, 07:55 AM
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Originally Posted by Hondaracer2oo4 View Post
Ok Zues, that makes sense. I will swap out the old cam gear with the new distributor.
Your camshaft will thank you for it
Originally Posted by Hondaracer2oo4 View Post
No I was not setting the base timing with the with the vacuum line unplugged and capped. Pinching it off with some vice grips should suffice, correct?
No, if you don't disconnect the hose from the diaphragm it will hold the vacuum it has and give you false readings - disconnect and plug
Originally Posted by Hondaracer2oo4 View Post
Like I said some of this stuff is new territory for me, what do you mean by mechanical advance? The distributor is brand new.
Inside the dist are spring loaded weights that move out as the rpms increase
These weights advance your base timing as rpms increase to give you power
Your vacuum advance is pulled in initially by manifold vacuum at idle to help with your offline/offidle acceleration
As your rpms increase, the vacuum advance backs off and the mechanical advance starts to engage
The weights are stamped with the total advance they are capable of
A pre smod dist should have 15 to 17deg
There is a small window inside the dist, in the baseplate under the reluctor that you can look thru to see the stampings

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post #18 of 22 Old 05-16-2013, 07:23 PM Thread Starter
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Thanks guys for being patient with me while I try to catch up with this stuff. Everything makes good sense.

Disconnecting the vacuum line from the advance on the distributor so that it has no pull on it, then plugging the line to make sure that its not sucking air should be the only culprit of a wandering timing mark. So if I disconnect and plug the line and still have a wandering timing mark where should I head next?

I tried to get to doing this today but cutting firewood for next winter took priority. Should be able to take a look the next few days and report back with my findings.
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post #19 of 22 Old 05-17-2013, 06:17 PM
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did you check for leaks at the adapter and head to manifold gasket?

I don't feel like working on anything at this time so i sold my yj.
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post #20 of 22 Old 05-17-2013, 08:07 PM Thread Starter
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Which adapter and manifold are you referring to?
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post #21 of 22 Old 05-23-2013, 10:08 AM Thread Starter
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Well I plugged the vacuum advance line and attempted to time the motor but the mark still is all over the place. Now I have to admit that maybe I am not using this time light correctly? It is a Sears Craftsman Professional, it has digital read out with the tachometer reading and option for advanced timing. I don't have any directions with the light and I can not find any on line. If I connect the plug wire on the light to the number 1 plug and shoot it at the flywheel I get the same flash as I do when I don't connect the plug wire at all! This does not make any sense to me, can someone explain that? Thanks!
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post #22 of 22 Old 06-07-2013, 06:55 PM Thread Starter
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Could it be a bad ICM??
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