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RPM's go way up when put in drive and 4lo only with brakes on

I had a bad MAT sensor do that too. Always check for a loose vacuum hose if happens after working under the hood!!!
 
MAT huh hadn't thought about that but I doubt it, keep reading. Vaccuum is one of my first thoughts but keep reading.

After finding out that if I unplugged the TPS it would calm back down I did the cheat and put a switch on the TPS wire (flat connector wire with .6ish V at idle more at WOT) and it calms it down right away. I do not like this as a perminent solution but it was better than listening to it idle at 3000 rpm. Even a balanced and blueprinted 4.0 sounds like it is about at redline at 3k. ha.
 
That is a new one for sure! I'll have to remember that... I was going to suggest checking your tranny fluid level and the shift cable + linkage for the auto trans shifter, those have caused similar issues for me before. My old 96 XJ would give me an RPM flare after every hard stop because the fluid was a bit low, stopping hard made it slosh away from things in just the right way to lose hydraulic pressure in the trans and it would effectively end up halfway in neutral.
 
So I read the better part of 22 pages in that thread and in my mind I have done most of the items discussed. I definitly did not adjust the TPS lately and did that this afternoon, started at .73v and ended up at .825v (to be technical). This was on the ECM side of the harness of course. It definitly changed things, It still revs up at start up but not as high more like 1500-2000 (not 3000) and it will correct itself eventually. Sometime the correction is pretty quick 5-7 seconds and other times it hangs up for a while. Temp of the motor was probably in the 40's so I expect a raised idle of maybe 1000-1200. This is a long way from a daily driver but it sure would be nice if it worked right.
 
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