ok. i have a sidekick built in japan in late 89. reg says 90.

ive been looking at my throttle body as ive been having some idle and vacumme problems. and ive been hearing the 89-90 throttle bodies were different then the newer ones. ive lookedup newer ones and they look the same as mine so has mine been swapped out for the newer design? with 330,000km on the truck i wouldnt question the engine isnt the original.

The throttle body's are made by Mikuni, but I don't think there
is a big difference in design.

Idle trouble high or low is adjustable, and the cold idle is controlled
by a wax pellet that melts with engine water heat and allows the air
bypass to close lowering the idle.

There is a typical high idle "problem" which is fairly common.

What problem are you having?

Wild

cold idle is 2000 rpm, which doesn't bother me, but sometimes when i restart or i stop at a light it likes to rev up and down. doesn't matter if its idle or if i hold it at a higher rpm it still has some fluctuation. its worse at lower rpm it likes to go from 800 to 1500 normally. its usually once it gets out of its cold idle.

its got an exhaust leak at the down pipe connector. its had it forever, Ive replaced the gaskets twice now and it keeps blowing out the gaskets. it also has a weird problem that when its cold my brake booster doesn't seem to work. i haven't traced that problem down yet either.

A high idle tends to reduce the vacuum effect, but with your strange idle situation
you might have a bad brake booster or a leak in the line feeding the booster.

Give that a check and report your findings

91 and newer has a different idle control system.  check out http://kick-fix.com/index.html

it will explain everything.

98% of the time, a cyclic idle like that is indicative of a vacuum leak issue. Check all your vacuum hoses/connections and a leakdown test as well.

well. i hooked up a vac guage right off the brake booster line 17hg. then moved it right up to where it comes off the manifold same readings. although the vac line is cracking and spongy so im going to change it. vac numbers dont change from 1500 to 5000rpm. it does drop on accel and when i rev but once i let the throttle level out (either back to idle or holding throttle at high rpm) it drops to below 5hg on accel.

dont know what it should be but it seems a bit low.

vac guage doesnt change from cold start all the way to warmed up.

with brake booster line removed and vac guage mounted in its place it still has idle problem where it revs up and down.

mine does that if the throtle position sensor is not in the right spot.

ok. another update.

finally got around to getting a tee fitting to hook the vac guage INLINE with the brake booster, so now my booster is hooked up and the guage is monitoring the pressure seen at the booster.

it holds at 15-17hg. truck can be shut off for 5 minutes and still holds pressure. when brakes are applied with truck running it drops to 11hg then when brakes are released it goes back up to 15-17. no change with engine speed.
i cant find any specs to see if this is all working right.

ill be checking it all out tomorrow morning (its been cold enough in the morning to trigger the problem lately) see if theres any change.

The #s look ok, the booster isn't leaking if the vacuum stays the same
after the engine is off.

Check the throttle kicker and throttle cable for binding, I've replaced my
throttle cable 2 times now because it worn out and broke, you might be
getting some binding because of that, it starts to fray the cable where
it goes through the fire wall, above the pedal, look there for cable damage

Wild

throttle cable has been replaced after i found it to be only 2 strands still connecting it. found out on a long weekend, on sunday, on vacation 9 hours away from home. no parts stores had any stock, dealer had one 3 days away, and NO wreckers that were open had any sidekicks at all. ended up finding a local used car dealer with 2 out back and found out he had a jacked up one in the shop and is a suzuki nut. got a used one off him and made the drive back home.

throttle cable made no change to idle problem.

went out in the morning and found it was at at same pressure (17) pumped the brakes and went to zero with truck running. stayed like that till 5 minutes driving and went back up to proper pressure. its odd that it works fine until it gets cold. is there a check valve or something im missing?

Ya, sounds like a defective check valve

ok now where can i get that part from? from what ive read its in the vac line. would a universal one work? i hope this is the problem cause thats a cheap fix if it is.

Ya, it's just a one way valve, designed to keep vacuum in the booster
for 1 or 2 stops when the engine has died.

I would go find a NAPA auto parts and tell or show them what you need,
I can't imagine it being over $10

Wild