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Idle high after cleaning throttle body and lashing valves...
topic intermittent idle controls.
and gross , idle slow speeds.
why is coolant at 169F, this is wrong.
is it in closed loop? if not the LTFT means nothing. but if it is in closed loop that LTFT is very very perfect. -3% percent,
the 200 idle is the egr main sticking open. at idle.
top contender. some valves (main) defy cleaning, and still stick at every other stop signal.
before the EGR was dead. now that you fixed it (elect, vacuum and exh paths fixed) , it now for the first time in years, the main must close every time. you stop,. it cant because it sticks..
the EGR main is part that is a tune up part, in that no EGR lasts for life of engine, so is not throwing parts.

"Does an inconsistently dropping RPM during the warm up cycle
or hot engine eliminate the Idle Speed Control?
Not sure if there is a differentiation between a consistently dropping rpm and an intermittently dropping rpm." ? I dont know.

but you can test these out each
Unplug the EGR main hose ,or more easy, the top of egr TB nipple. the put a short tube on the nipple with a screw in the end (no vacuum leaks allowed)
now reach back, and push the egr man closed, did it close? good
now drive, its fixed now, right, no more idle loss.

island kits: for sure old cars are very hard to stock up on parts, as some parts fail randomly,
but here is list
all tuneup parts.
ISC maybe, but never seen one i could not clean and make work.
EGR, (if killing it is not an option, but you might need a new one in 100k more miles?)
IAC, are not sold new. great idea is to get a whole used, TB> for sure.
brake shoes, and pads
PCV valve, very cheap.

i dont think your ISC is failing, but it can be cleaned easy. soak it overnight in carb cleaner, submerged. (hose blocked, and tilted so it holds the cleaner)

its not stalling for AFR reasons, so says the scan tool.
so that leaves the EGR.
can i presume this a fail failure of idle
never cold !
only warm above 150F (IAC closes and iSC gets the full job NOW)
and hot?

the ECU has staGES, SO....

Does it fail as stop signings,? i dont when and or what conditions of engine heat or moving car.

I think i've solved the idle issue with a new EGR main valve. I blew in the large tube while covering the main hole and sensor hole and I could hear some air leaking out the old valves port. I think that was the problem. An incomplete seal. If I knew more about EGR's and paid attention to your documentation, I could have diagnosed the old one after I cleaned it. I'm learning.

I'm curious if the large tube hose going to the egr valve should have a hose clamp on it? On my vehicle, there was no hose clamp and I'm wondering if the large air hose to the EGR valve can cause idle issues? It didn't have an enormously tight seal.

I'm glad to have this one solved. Will drive it some more, but it seems fixed. I had to screw in the fuel air a couple of turns to bring down the idle now that there was no further air leak.

95 Geo Tracker, Build Date 1/95,16v, Fed, Cami, 4x4, MT, Headed for Grenada.
GrEaT !

no clap, its has nothing there or a partial vacuum , it sucks itself on, if hose not too big.
the main only has 1 hose.
the modulator has 2 vacuum hoses and 1 large putt putt hose, the bark hose.

the main is in the back of the intake at fire wall
the modulator is up top side.

at idle the modulator is dead. (2 ways) at idle.
the main is 100% closed at idle .
what nipple are you blowing???, EGR mod or main.. (main is the exhaust valve.

tell me what part leaked.
or mod?

the main is aluminum, the exh, valve there, must not leak. the vacuum nipple must not leak. blown,. (or sucked)
the mod is plastic and normally leaks, Q to P (or reverse) but the large bark tube, never leaks. ever, it's diaphram.

you are on track, it seems.
good luck
There are two hoses that go into that EGR Main. The little hose that is on the top cap and the big one that goes onto a bent pipe coming out of it. I blew into the bent pipe while closing off one of the engine exhaust ports and I could hear air bypassing the valve to the other side.

Will drive it some more, but so far so good. Today is not hot and that's when I saw the most issues. So, I'll see how it does in the heat.


ps. To my surprise, the egr temp probe came right out with little effort. I did that first while the egr main was still mounted to the manifold. Easier to put torque on it.
95 Geo Tracker, Build Date 1/95,16v, Fed, Cami, 4x4, MT, Headed for Grenada.
that is the EGR modulator. #8
it's tricky to test that, and can not cause idle stalls or idle issues, it only operates, when car is moving, and throttle off the idle stops.

that is the bark tube #13, the large tube is a direct shot all the way to the exhaust #4 port, this is normal, there is no valves on that side.ortube.
this 13 tube is the tube that senses exhaust back pressure at all times, running. (engine load is sensed via CAT converter back pressure)

the main valve #5 is the valve behind the intake manifold
the plastic valve is the modulator. #8

P nipple goes to plenum (via the VSV valve)
Q tube goes to the EGR main steel nipple at #5
bark tube #13 exhaust goes to the bottom of the modulator valve. this tube is never blocked. it barks at all times running.
The Bark tube 13 goes to the bottom bark large nipple on the EGR main 13.

[Image: 92-95-EGR-16v.jpg]
I thought EGR main is number 5 and the modulator is 8?
95 Geo Tracker, Build Date 1/95,16v, Fed, Cami, 4x4, MT, Headed for Grenada.
There are 4 factors that stop the main, #5 from being open at idle
1:no vacuum at P above (ported vacuum is dead)
2: VSV is closed via ECU command.
3: the main #5 has an internal spring inside, keep it close.\
4: the main #5 valve is not stuck open. its closed. via all the above.
if not idle WILL fail (drop). or stalls.

#5 usually fails every 50k miles, and on most are no longer usable after 150k mlies.
seem some that pass bench tests but stick only hot... can be a real pain that.

on the other side of the coin, getting rid of 51s or passing smog is a much longer story.

stalls or loss of idle controls or way low IDLE:
keep in mind, if #5 is closed, (check it, clean it test it by hand)
you can at any time.
pull hose 16 at line 14
then put a screw in the end of 16
to test idle. issues.
any time.
which proves the EGR main, is not contributory.

it is , i corrected my drawing error, sorry for that,
i added lots of hints to the drawing.

there is one more logic path that stops EGR main from opening.
that is the modulator.
the modulator , in the absence of"bark back pressure waves."
defaults to venting, killing all EGR flow.
so if the bark tube is dead, there can be no EXH EGR flow. 6 different ways.
(09-21-2014, 09:55 PM)cosmic_splatter Wrote: I thought EGR main is number 5 and the modulator is 8?

see my new , mod drawings.
lots of facts on one, spot. like it?

[Image: modulator-sectioned.JPG]

Very nice diagram and explanation!

It seems like these things do not often fail completely. Only give you hints of problems by the valve not opening or closing all the way.

What is the purpose of the modulator? Does that release excess vacuum pressure? Or is it a one way valve to allow the plunger in the EGR main to release?

95 Geo Tracker, Build Date 1/95,16v, Fed, Cami, 4x4, MT, Headed for Grenada.
most the time the EGR main fails at every traffic stop, it sticks open. car stalls.
this is so common,

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