Toyota Repair: engine stumble, throttle position sensor, engine vacuum

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97 tacoma, 4 w/d v6
engine stumble at 1500 to 2500 rpm when driving on level rd. does not happen under acceleration. seems to be related to engine vacuum or throttle position sensor. this is not a skip of 1 or 2 cylinders. the whole engine cuts out.
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I'm assuming that the check engine light is not on,is this correct?
When the whole engine cuts out what happens after that?
Is it like you turned the ignition off?
You may have a clogged up fuel filter or possibly a fuel pump problem.

the check engine light does not come on. the stumble is momentary but consistent to that rpm range when holding at an even throttle and not accelerating, as if the ignition sw. were turned off and on.
Answer -
This sounds like an engine misfire but I don't see how that could be because the computer monitors for misfires and turns the check engine light on so I have to assume this is not the case.
Has anyone worked on the engine recently, even normal maintenance or spark plug change, before I go on I'm going to ask you to check one thing that could cause this, open the hood and look on the right side of the intake manifold(standing in front)close to the diagnostic connector is a ground bus connector, it has a bunch of brown and black wires connected with a 10mm bolt, make sure it is tight, let me know if this helps if not I can probably come up with something else but we need to eliminate the simple things first.

those ground mconnections were the first thing i checked, i had trouble with them before. no work has been done recently. the problem is rather intermittent. it has not occured in the last 2 days, but i am sure it will be back. if it were the throttle position, air volume or one of the oxegen sensors intermittently failing would the check engine light be coming on ?

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Yes, any of those are input signals to the computer.
It uses two trip dtection logic, the computer has to see the condition twice in order to turn on the light so there could be a trouble code(pending code) but the check light will not come on until the same condition happens again.