EGR woes

[cygnus58]

your input is welcome here Jerry, far from pollution as many of these systems do operate the same in theory.
not sure what you are saying about purge (VSV? right)
when i checked it on bench it does revert to vent mode without voltage applied, vents output side thru filter to atmosphere right? just seems mod is not fully passing enough to EGR valve. ie not enough back pressure input.. the funny thing i meant was vacuum acted like electricity (under load, drops) the gauge read much higher without EGR valve "in circuit" and that doesn't make sense to me. Not thinking too hard about that tho..but maybe i should?
I got two VSVs, a MOD and a MAP from some 90's Toyotas at a local scrap yard today for 20 dollars, but got the GEO VSV working when I figured it out. I thought the slug should move but realized it just pulls on the valve plug thru magnetic proximity from the coil being energized.

I doubt the MAP will do me any good as curves are likely different. (plug is same, and same size also), Denso 100798-1760, would do a person good as web pricing is over $250.00!!
Yes, like a succubus, Renix (renault/bendix) can steal well needed sleep from you as a devil woman.....

[jtgh]

yes, i know that devel woman, watch out.
good purge = vent yes.

the gauge reads much higher without EGR valve "in circuit" and that doesn't make sense to me.
explain that, it seem odd.
ascii art (not)
EGR >>>> T >>>> VSV >>>>>TB nipple
this the connection? or?

T = vacuum gage,
is your EGR vacuum diaphram ruptured? leak down test on it.?

vac should go high and hold.
same as plugged , only faster plugged.

[cygnus58]

no leak down with manual vacuum applied - 4-5 holds valve completely open - valve held open for as long as hose bent.
mine goes - intake to vsv to mod to egr, vac tee is at egr, reading about 2-3 lbs at highway with egr included. much higher at same point w/o egr included..
weird huh?

sorry to confuse

[jtgh]

intake to vsv to mod to egr, vac tee is at egr,

at egr nipple, is the T, got you.
now

2-3lbs, ( is this inches of mercury, bar, or ?) which vacuum std.|?
so when you pinch the line, at EGR nipple , the pressure (vacuum) increases strangely.

I suspect the MOD valve is causing that strangeness.
The presssure of exhaust pushes its diaphragm (mod) up, and this allows some vacuum to be gated (linearly) to the EGR ,
i guess the MOD valve pistion in the valve has some kind of natural feed back.
I think it is a natural event. ( but that is my guess,not fact)

if i had a bad one , id cut it open and look.

the wierdest part is the relationship of the exhaust back pressure and the MOD valve.
(no one knows how much Back pressure it takes to make the mod valve work properly)


cheers.

thanks for sharing too,

[cygnus58]

no Jerry tee is at EGR valve vacuum input, now should seems stranger.

I am gonna try some old throttle cable with frayed end one more time with drill from egr port thru intake bends toward head this weekend and see if that adds enought back pressure to mod for more egr valve opening.

thanks for hanging in there with me....

[cygnus58]

took off exhaust manifold to make sure intake had no carbon in bend, did get a little out and blew air thru with no restrictions from one end to other.
Teed gauge into egr valve and put in glovebox. Can use for other onboard vac measurements if needed that way and now can tell at a glance if vsv, modulator are working. Still only about 3-4 in reading.
Put video camera and led light under hood aimed at EGR valve this morning to confirm it is opening. Never more than about half but maybe not required. I'm thru with it. I guess with some EGR and advanced timing, valve life should be fair.....Must be doing something, was able to advance timing to a point where it did ping a bit before at load, that is gone now.
have a slight miss at idle under no load (park, neutral) Plugs are new yesterday, i guess wires or injector would be likely cause of that. Always had it. Not too concerned. When money is better will try wire set. needs Timing tensioner and rear wheel bearing first...

[jtgh]

you are conserned with the Egr, not because of Code 51 , but because of driveablity issues.
http://carfix.stufftoread.com/sensors/egr-profile.JPG

this is all i have on EGR profiles.

if egr is weak, most likely exhaust back pressure is bad or EGRmod is out of calibration.
i would never suspect vacuum. (unless dead).
however:
"Still only about 3-4 in reading."

the 3 inch reading exactly where is that T'd in , at.?

I do notice the vacuum is ported by the throttle valve so i suspect no vacuum is at idle.
or little.

the manual only shows checking the mod valve , only that it works, no values.
the egr MAIN valve must gate fully on with 20cmHG VAC.= 7.8 inches of HG. ( and the stall test , bla bla)

the other numbers:
tests, below 8200 feet altitude.
engine coolant above 136 and on some cars 158 deg , F.. depends on year.
some cars require 3500 rpm to attain full egr stroke,
on other years, 2500 rpm , wheels off ground (rear) and in gear 5th or max).[95']

here is my new map page. Both factory and personal readings.

too bad they dont spec out the mod valve for pressure in put, I might try to measure that on mine and post it. (RPM and pressure , stock at MOD valve port "A" ,exhaust input)


cheers.

[cygnus58]

thanks Jerry, that data would be interesting (pressure in at mod valve) i don't have factory service manual, come to think I may call garage tomorrow and ask them for that data also. The 3 inch reading is teed in exactly at EGR valve vacuum input for valve movement.
And yes all vacuum to VSV is zero at no throttle or full throttle.
EGR does gate fully on at about 5-6 applied with Mitivac.
Have driven at 55-60 (no tach but i beleive 3500 rpm sounds about right)
The mod valve I got at the yard from a 90's Corolla works exactly the same as far as vac/inches in/out to EGR valve with this 1.0 3 banger back pressure. Exhaust is new from front to rear also.

thanks for your continued input.

Joe

[cygnus58]

new added wierdness today, all vacuum to EGR valve stops at over 60 mph regardless of throttle position, i cant even begin to understand that. We just wont drive her over that speed anyway.
Cant be VSV, shouldn't be Modulator, or could it. Vacuum from TB above throttle plate wouldnt care, this is becoming quite a mystery....
took out EGR valve and super cleaned with Hoppes and gumout and pipe cleaners and gun brushes. it held vacuum while apart for over 20 minutes with hose clamped by hemostats.....

this isnt rocket science but may be more complex....beginning to love that Renix...

[jtgh]

all EGR stops at WOT, that is in the rule set.
over 70% on some cars, others a tad diffr.
no EGR at WOT , nor At idle.
nor over 8200 ft. alt.
and on some 94 and newer , and slightly older cal cars. the car must be moving.
moving = VSS clicking.
and then you must be over 2500RPM on 94 on up.
the sad part is ecu,expects this and has mixtures settings just for this amount.
if missing , this magic amount , the AFR will suffer.

EGR does have good points.
reduces , pumping losses,,
reduces , fuel and temperatures in the cylinder while deaccelerating, cooling valves and increasing MPG.
log ago they learned a few tricks to have it actally help some aspect of driving.
there are other rules, engine must be hot. (Im sure i forget a few)
but not here, hopefully.
EGR-repair-methods

i suspect yours will be ver close.

cheers