coolant flowing between iac and isc ?

[john110]

You`ve got so many infos(a great thing), I miss those link.... After reading your text below, I`m wondering if is there a list for this ? "....the ECU under special cruising situations opens the valve..." a list of situations ordering the ECU to open that valve to let Mod and Egr to do their jobs.

Another thing, Last yeat I removed the Cat on my 94 Tracker and installed a strait pipe thinking it wouldn`t change anything. Huhhhh I can now see that it wasn`t such a great idea.

"89-98:
The ECU commands the EGR to open via the Vacuum Solenoid Valve VSV) and then MOD, measures the pressure drop.
The Vacuum port at the manifold is ported and has a varying vacuum to the input of the EGR VSV.
The ECU connects electrically to this VSV solenoid, the ECU under special cruising situations opens the valve and passes this vacuum to the
EGR MOD valve. The Mod valve (aka: transducer in newer Suz. manuals) then modulates this vacuum even more by virtue of the exhaust back pressure.
The output of the Mod valve passes to the MAIN EGR and it opens proportionly to these inputs I have just described.
This is what happens under normal driving. Any Failure sets DTC 51 , for failure of valve to open , close or heat up the thermal probe.
And all 95 and all Calif cars run a thermal probe test.

more.. 89-95:
The MOD valve , only allows vacuum to pass to the EGR valve under limited pressure states in the EGR exhaust port.
( you must have exhaust back pressure!)
Due to that fact, a missing CAT can cause the MOD valve, to fail completely. (missing, rodded-out, blownout,melted, broken up)
* heads up CAT bashers ! I see you with that broom handle. bang, bang.... inside that CAT, you are a naughty boy, your are....!
The results is an engine that runs badly."

[john110]

Ok Kick, you can forget about the last question. I found it within your pages. not idle, not WOT, VSS faster than 0, I think warm engine....

I was a little surpirsed is that the "bark" pressure can flow until the Mod. Without a CAT how much of that "bark" pressure is lost, most of it ?

[john110]

I guess most answers are already on your site !! "If the Cat is missing or rodded out, the MOD will be dead. (the bark tube will be way too weak ,to do anything)"

[john110]

Kick I`ve tried to find answer of the next question but didn`t find any.

1. Is the MOD influenced by all cylinders or just by cylinder no 4. Is the back pressure from cylinder no 1 or 2 can go up in exhaut no 4 tube and go to make pressure on the MOD ?

2. Your chart shows that when exhaust valve open, just after, backpressure is sent to the MOD so EGR is opens. It also show that after that wave it seems to have a suction that close the MOD. It would mean that MOD is opening and closing for every cylinder cycle, right ? (only on cyl 4 or on all ?)

3. The main reason I`m asking is when looking at video, on acceleration EGR looks to keep being opened. Is there something I`m missing ?

Btw, thanks for info about the Tachometer/speedometer/cluster info. I`ve been able to reconnect it.

I got a spare engine , the one that was in my Tracker when I bout it. With all infos I`ve read here I really think I`m going to rebuild it, paint it etc. I also wanted to know(understand) the vacuum system to be able to make adjustment and to know what to look for when there`s a problem.

Thanks, John

[fixkick]

good qustions
the mod only measure the #4 pressure. or engine load. so the ecu Assumes that all 4 are under same load, and are. 1/4th each.
the whole purpose is to measure load, and match that with proper EGR flow.
in between #4 putts are others, that whole have to travel far to reach the MOD, and before the next fast coming #4 putt (or bark)
keep in mind the mod is tuned to work only on stock car.
the egr needs to work for 2 reasons,,, pass smog.
and more important is to stop PINGING. (Detonation)

i have no way to view the diaphragm valve in the MOD, nor do i need to.... what matters is clear path from MOD to cat, brick.'
the rest is natural. (there is no stopping the any of the 4 exhaust ports from working, only the #4 egr path, can fail.
weather 1,23, have influence, im not sure. and a moot point?, considering what can and can not fail.
i think it will when the cat melts, and the EGR goes NUTS. (a double loss of power)
some years ecu, if code 51 set (usa) the ecu may go to limphome or just go richer to save the engine from ping damage.

for sure the mod is tuned to your car...stock

---

in 1999 , the ecu does all this is software ,then opens the egr motor.
no more vacuum junk.

[john110]

Thanks for the answer Kick.... for sure you`re the one who can give the "deepest/(knowledge side)" answers.....

Btw, I looked at two spare exhaust manifolds I have, they were both clogged at the inport that bring exhaust gas to MOD...... just few weeks ago I had no idea it was a clogged port, even a port !! I discovered it after seing all the pics you have....

[fixkick]

yes most are.
all ive seen were. like this.
it looks like iron that carbon there, and invisible port
that is why its is best to do my bark tests.
ive helped 100s work through all this egr, pain.
it can be very hard. one car has 3 failures. another , all paths blocked, and vsv dead.
the only hard parts of these cars , all cars, is the ECU software can vary, do odd things.

like why some ECU software hunts the idle speeds.? very odd.


if you remove the bottom mod tube and it dont bark
then remove egr, main., use a cork to plug vacuum side (right) and let the left egr port free vent
and start engine, if that dont bark , the #4 tube is packed or the head tunnel is packed, my 97 was both packed, with carbon.

[john110]

Kick, I`m going to buy a vacuum pressure tester in the coming weeks. I`ll add a T plug in the vacuum line just before the egr and will install the tester on the windshield to be able to see it when sit in the driver side.

I would also like to install a compression tester to check live the pressure that goes from exhaust to MOD. So I would be able to check both lives. However I have to fix my exhaust first as it isn`t air tight.

I was almost thinking of installing two gauges somewhere in the Dashboard to be able to have a look at it anytime. would it be a bad idea ?

[fixkick]

vsig:94TBI
LEAKS IN FRONT OF CAT BAD TO O2, AFTER ONLY SMOG DRIVER. SURE BAD.

been sick for 3 months, so stopped taking meds (damn liptor) now feel like 19years old.
wow, now i can read a page and keep all 5 questions in head and not forget.
im 68yo
We have joke, my doctor retired, and now, im all good now. funny that....

yes vacuum gauges are real nice, see it bounce , bad news or EGR stuck open.

the egr main line is ported vacuum this is no good, unless egr is being tested,
THESE NIPPLES all these are hard vacuum 20" steady at idle.
http://www.fixkick.com/engine/8v-Show-bo...ge_28.html

id dont think you can do that, mod center bottom hose, its too fast for any gauge,(cept electronic barometers)
just listen to it or feel it pulse to hand.

Gauges:
vacuum , voltage and fuel pressure are my 3 favorite, add oil pressure and it's heaven,, like a pilot has. for same reasons.



good luck to you, and im pulling for you!


my back door
85deg water, and huge beach.... on vacation

[john110]

"vacuum , voltage and fuel pressure" I think I`m going to had those gauges in my project. That would target right away différents problems, being able to see those while driving is a nice +

Good to hear to you feel better.

85F up there...Huhhhh, it`s 5F right now here....