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Old 01-28-2013, 11:23 AM   #2
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Re: Need Some Advice on Jeeps

The original idle spec for the 'Six' was probably more like 850 to 800. The small screw could open or close the throttle plate a little, but the computer is going to try and control the idle speed to the original rpm - until the throttle plate is opened far enough that even with the Idle Air Control Valve all the way shut the engine is still turning faster than the computer prefers. (If you unscrew that adjustment till the throttle plate is entirely shut - it would probably run fine once started and running, because the IACV would be opened a little more by the computer at idle. However I think the throttle plate has to be slightly open for better starting from deep cold. Thats my guess anyway).
I would think its more likely that you tachometer is 'off' a little due to aging rather than that the computer is running it at 1000 rpm on purpose.

When its cold you can expect some resistance going into 2nd, because of the effect of stiff oil, and snychros that arent as effective as new. Lots of folks use a heavier trans fluid that the original stuff. I know guys using 80W trans fluid in manual transmissions designed for Mercon III auto trans fluid - and they have very noticeable stiffness until the trans warms up.

I kind of thought 16 mpg was considered common for the 4.0 liter Cherokees, but that might be with the automatic transmissions. The expected mpg with a 4 by 4 pickup might be different (lower) based on the final drive ratio in the differentials.

I have an 86 comanche with the 2.5 liter four and the 5-speed transmission used at the time (a different 5 speed was used from 87 onward). I get 25 mpg on the open road. Mine has no options; no power steering, no a.c. no all wheel drive. I only wanted the 2.5L four cylinder engine.

Im looking to find an 86 - 92 Cherokee with the 2.5L engine, a 5-speed trans and all wheel drive, for use in the hilly parts of Central America. And I want it with a bad engine & clutch, so it will be cheap. Havn't found any yet though.

I think there are other Jeep forums with more activity.
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