Idle high after cleaning throttle body and lashing valves...

[cosmic_splatter]

Fixkick,

When you say set the rpm to 600 rpm with ISC unplugged. Do you mean unplug the electronics or air supply line? I'm assuming electronics.

I will be attacking this problem when I get done with the rear end work early next week. I think I still have an issue. I adjusted the fuel air and everything seemed to be working ok, but I think I may be masking a vacuum leak issue.

Rinoman gave me the instructions to use Tuner Pro with a 1202 ECU. That software will show closed loop status.

John

[fixkick]

first off setting idle is the last on the list of all things to fix , tune or correct.
and if you have illegal leaks now, they will only get worse, and setting idle speed (duty) is just chasing the tail. (like catching a monkey)
(imagine 4 leaking injector cushions.... they will get worse)

My comment on 600 is when you have no way to set Duty Cycle (tools). it's a shade tree fix. (ball parking it)
if the scan tool works right, you can set DC with it.
I have the Tech1 page for that here, see all those PIDS?
http://www.fixkick.com/ECU/Tech1/full_scan2.html

see parameter 17? that is DC, i think, im no expert on obd1 scans, i have no tools for this. they are very very rare here. in the USA. most tech1 are now lost ,or broken....here....
but in theory you could set the duty cycle DC with this, PID 17, the number in the box is how far open the ISC , is now.
In theory you could close the bleed, screw, and hit 50% (the number there is the error in RPM and the ECUs correction via ISC dutycycle. ) at 50% the ISC pulses at 0.0025 seconds. 1/2 way.
so lets say you close the bleed 100% oops cant hit 50%
so you find air leaks. and fix them. I blocking all normal paths lets you find the abnormal paths, (normal are a,b,c,d) per my drawing.
NO scope, no Duty meter, no scan tool way. next. my goofy 600 hack.

Shade tree way:
unplug the elect line, if the isc works ok? "trust"?, (closes) or pinch the tube air if , unsure. (keep in mind, old bad ISC can in fact leak)
if you pinch it, you effectively kill all air to the engine,
why?
(IAC is proved not to leak hot ,first), TV is not stuck open with crap or cable set too tight , leaving only one supply of air left the bleed.
my engine drops to 400 rpm it the iSC pinched, some may stall..... depends on the totality of air leaks. and engine health , new engines, can idle real slow, not old.


id do that tests, all the a,b,c,d tests, see my intake drawing there, and all air paths,
you can prove they are all closing, and prove that there are other illegal air leaks, easy.

good, having a real scan tool, is very good idea. closed loop is a goal, as is the long term fuel trim.

Scan tool.
1: does the 02 work?
2: does it hold closed loop status at idle.?
3: if yes, then what is LTFT. ? +40 , -40% or near zero ,, ideal is about -5% (this means the FAM runs a touch rich, and the 02 , servo pulls out -5% fuel to compensate)
if say the injector cushions, or the booster leaked air, the reading would be like +20 to +40.
the reading are POLAR, they can add fuel or subtract fuel,
modern cars use % , some other old cars and these old sidekicks use a binary scale.
parameter 13 long.
0 lean, 128 perfect, 255 rich.

the fsm shows 118 is normal, for hot closed loop. idle.
i think lean means it was rich actual and the ECU went 118 leaner. (tricky huh)?


what is the RPM hot, with each path proven to be blocked, a,b,c,d.... ?????

keep in mind, the LTFT will warn you of fresh air leaks (unmetered air , buy going + xx % )
and that DUTY cycle way off warns of illegal metered air , leaking, by GOING LOW.
low duty is sign of , leaks , a,b,c,d paths.
high + LTFT is a sign of, fresh air from any place. the ECU adds fuel to illegal leaks, until it gets out of control, the bogs.

metererd leaks do not upset, fuel balance. only way high RPM, if the ISC loses control at 0% (0 means im closed)


I adjusted the fuel air and everything seemed to be working ok
what does that mean? you touched what?

---

ill do a duty cycle session, with scan tool
i see, closed loop fail. bam, idle means nothing now, AFR is BROKEN. fix that first.
ok , my o2 was bad (pretend,) or the exh crack made it lie, i fixed that and CL , is true , at idle. Closed LOOP is CL flag a binary single bit.
CL =ture
I look at LTFT its at -5% that is a good sign but mine is +30% oops, that is bad. (its adding huge fuel)
so this is a classic sign of a huge air leak. (or even a weak MAF) the ECU dont know why , it only know what the 02 servo loop shows. its lean.
I have and atmospheric leak, not a stuck open isc or TV stuck open or the bleed set wrong, this is REAL air, called UNMETERED AIR.
I test my MAF carefully , i clean it and its showing the correct grams /sec, at idle. (its not the maf)
so I uses any of the 5 ways to find air leaks. (liquid fuel spray, water, propane, or smoke machine, or total dismantling & inspection'ouch")
the can happen from the trailing edge of the MAF all the way to the intake valves in the head.
all seals, all gaskets, are suspect,
1: i find the brake booster hose , when pinched, or blocked, solves the huge LTFT offset. sure, its bad.(diaphram crack)
2: the injector cushions died long ago. and leak air.
3: my 1997 the rear of that huge , alumin. induction tube. mount , in the rear, not seen was broken off and the casting had a huge air hole in it. sucking illegal air all the time. bam.
4: the intake boots are bad. cracked. (the huge AIR pipe main Induction to air cleaner +MAF)
5: intake gaskets bad.
6: TB gasket bad.
7: a vacuum hose somewhere is cracked, many.

now only DUTY Cycle is way off, not 50% (LTFT is normal)
A: SET WRONG.
B. TV STUCK OPEN OR or someone fiddled that factory screws, on TB , bad boy.
C: the bleed is unscrewed 100% or missing.
D: the IAC leaks. air, hot. or the hot water never makes it through its guts.... oops, bad water flow.
E: the ISC is leaking, the rubber ring looks like the moons surface, "craters" so i recal it ,using my Barnyard ways, i set the no touchscrew so the cone just does close it. 99%

i correct those then set the bleed, hot, CL, at 50%, im done. the ECU sets RPM not me, i can only change the DUTY.

[cosmic_splatter]

Thanks Fixkick! Idle was working normal prior to me doing the service on the valves. During that service I took off the throttle body, sidewinder tube and air intake hose. So, those are my prime suspects.

I need some remedial troubleshooting here as I've never tried to solve a vacuum leak.

1. When I pinched the ISC air line, I saw the rpm drop. Is this good or bad? What should I expect on a car with no leaks? How do I tell if this line has an air leak? If that valve is at aprox 50% at hot idle, I would expect it to drop the rpm. So, while I saw rpm drop, I wasn't sure if this is good or bad.

2. If I pinch other hoses and the rpm drops does that mean that hose is leaking? There's a little one that goes into the top of the throttle body and one that goes from the main air line into the valve cover.

3. The only screw I turned is the one under the rubber cap on top back of the TB.

4. If I run propane around the hoses, I wasn't sure how high it should be set. Should you have a lot of propane flowing out or just a slight hiss if fine? Should it be coming out strong enough as if you were going to light it?

5. Is it possible that someone set the idle higher and higher as the throttle body was getting full of carbon? That pathway of the fuel air screw under the rubber cap was full of carbon as well as the entire TB.

thanks,
John

[fixkick]

others reading this (my comments) DOES not apply to 1989/90, G16a engines, these 2 years have a very unique Throttle body, (no duty cycle air bleeds on any of these engine)


your very welcome,wow what great questions, all !!!
and there are lots of gaskets to fall off working here, the side wider has 2 sst gaskets that love to fall off, in the dark.
1: what rpm? RPMs matter, big time. need hard number, before and after RPM. in every case.
the key to understanding this is my graphic, drawing,with marks a,b,c,d. ?

those are the legal (not leaks) air paths. there are only 4, so if you block all 4, on a new car, the engine must stall with zero air inducted it can not run.
this sets a base line, zero air. car will not ever start again. with zero air.

on a hot engine, the iAC is 100% closed. leaving only 3 paths, if the IAC is bad, all other RPM errors are not important, the engine will scream with this thing leaking and the ISC goes nuts.
ISC means IT and its magic software. (called the ISC servo system.)
so if that is known for a fact to be closed, then Id pinch the ISC hose.
and rpm goes from where.? 1000? and goes to 400 or stalls.
usually it would stall. but if not, i screw the bleed in 100% gently do not damage its seat, just gently close it. CW, screw.
now IAC is closed,
now bleed is closes
and you pinch the iSC hose,(air) all air is gone. now. it must stall and never start again.
see this?

these checks (RPM facts) will disclose to me what is wrong, or if there are un-metered air leaks.

all hoses must not cause RPM changes, except do not pinch these
PFREG (this foods engine if pinched)
the MAP hose (you dont have it)
the PCV, do not pinch it or seals in the engine can leak, for this 1 hose, eyeball ispections only workl

the Brake booster hose can be blocked , pinching it is near impossible but it must be tested, to be 100% sure. un do it and block it , with my kit of corks.
there are not all that many lines, see them ,at end.?

hose 45 is ISC metered air line, if you block it , the engine will stall, or run very very slow. (if the bleed is wide open the engine might run real slow.) i can not predict bleed , setting.
on one car it was missing on this forum. ouch.



post
Thanks Fixkick! Idle was working normal prior to me doing the service on the valves.
During that service I took off the throttle body, sidewinder tube and air intake hose. So, those are my prime suspects.
(missing gaskets or the main tube rubber ring, was folded over, and now leaks like sieve.?

I need some remedial troubleshooting here as I've never tried to solve a vacuum leak.

1. When I pinched the ISC air line, I saw the rpm drop. Hot engine rpm before and after, i need real numbers, only.???

Is this good or bad? its bad, if it didnt stall, but no numbers no guessing by me.
What should I expect on a car with no leaks? i it will idle at 800rpm at any electrical load. if A/T in DRIVE TOO.
How do I tell if this line has an air leak?
If that valve is at aprox 50% at hot idle, I would expect it to drop the rpm. So, while I saw rpm drop, I wasn't sure if this is good or bad. (no tacho, no joy)

2. If I pinch other hoses and the rpm drops does that mean that hose is leaking? yes and no. depends on hose function.
There's a little one that goes into the top of the throttle body (EGR ported vacuum) and one that goes from the main air line into the valve cover. PCV

3. The only screw I turned is the one under the rubber cap on top back of the TB. good we can fix that easy.

4. If I run propane around the hoses, I wasn't sure how high it should be set.(set what?)
Should you have a lot of propane flowing out or just a slight hiss if fine? Should it be coming out strong enough as if you were going to light it?
let it rip, do so out doors with gloves and goggles, in case it flashes over, propane is forgiving unlike any liquid fuels.


5. Is it possible that someone set the idle higher and higher as the throttle body was getting full of carbon? sure, but you had the throttle off
and im sure you checked that the VALVE is 99.99% closed, or at .0005" (smallest feeler gauge on earth, mostly)
That pathway of the fuel air screw under the rubber cap was full of carbon as well as the entire TB. yes, it was very dirty.
we can not guess the actions of any PO. but i assume he did it all wrong, and in most cases, they did. over and over..
that is because they never read the FSM. its all there. (not the .0005 check that is mine, they tell you buy a new TB< for 1K buck.
1:TV closed 99.99%
2: IAC closed hot, if not closed, all bets off. for 1 and 2. what is RPM now hot? 800, 500, 1000s or 1500 or what, i cant guess these, it must be stated.
3: bleed, can be set last and should but we can fiddle it all we want to aid diagnosis. close it. what happens? CW. set it.
4: pinch the ISC air hose and then engine stalls, there is no air to run car now. zero air, zero run, zero starts.


thanks,
John

here they all are, sans booster.

[img] http://www.fixkick.com/sensors/EGR/92-95-EGR-16v.jpg[/img]

[cosmic_splatter]

Fixkick,

After I opened the EGR port inside the manifold, it appears that this would put the EGR system in play with respect to air getting into the engine. I'm wondering if the EGR main may have an exhaust air leak since this photo shows what could be black carbon coming out of the back of the EGR valve.

Is it possible that the air leak could be coming from the EGR main valve seal?


After years of running the egr main with a blocked manifold, wouldn't that put more air pressure on the EGR main seal?

I'll continue my testing today with the Tuner Pro software. I think I can fix the closed loop display and rpm issues.

John

---

[fixkick]

that is rust.

the pressure is about 1psi, max.
if use lips and block the port. you can suck on it and see all leaks.
it usually never leaks, air, due to carbon, packing the main valve shaft bushing.
it gets tighter and then sticks.

the rust is dark red. (dark orange is dust)
the ring in center is steel. and the outer lip
the body is alum. and i see only grease there.

---

there are many fail modes, ill try to list them
1ticks at every stop sign. (valve shaft, carbonized)
2: packs in carbon
3:diaphragm leaks.
4: any or all gaskets missing or on 1996 up, 3 gaskets missing (2 on sidewinder sst tube)
5: main body cracked, one guy managed to get water in there and it cracked below 32F, truly, near impossible. but he did it.

for the the shaft to leak air, it would have to be very very loose. any very tiny leak can in fact be corrected with the ISC, and does.
i think it can (shaft) only leak at cruise, but when closed, valve, blocks access to this bushing closed. (right)?

[cosmic_splatter]

Could I take the sidewinder tube off and plug the hole going into the engine to see if this circuit may be the cause of the air leak?

---

ps. is there a right side and wrong side with the sidewinder stainless gaskets? They appeared to have a dimple on them and I wasn't sure which side went where.

[fixkick]

WAAS-UP-DOC?

sure, there are many paths to leak.

i dont think so, the flanges are same shape so... gasket is up or down,
yes its just rolled dimple, it is spring like and can be reused in most cases.

if re-used them like 10 times, or more... they are sst gaskets. good for 8 years, EPA spec.

---

how is idle hot?

850 is max spec, hot. RPM

does the iSC pinch stall the hot engine?

---

the ECU will compensate for leaks.
it closes the ISC, more.
if the leak exceeds the ECU's (ISC) ability to drop RPM , the ISC loop is out of control and can even hunt.
no matter what the ISC MUST be able to drop RPM below 800. or it is by definition, out of control.

a prefect motor, the ISC is at 1/2 volume, or 1/2 open, 50% duty cycle.
the ecu can handle too fast or too slow idle, automatically with fast ISC actions.

[cosmic_splatter]

The idle seems to be ok. It's able to keep 800 rpm with a/c on and off and headlights on and off etc. So if I have a leak it's a slow leak and computer is keeping up. I'm driving it for a while to see if it gets worse. So far, it hasn't stalled at all. So, not sure why it went up after taking a test drive after the valve lash and timing belt procedure. I've double checked all hoses and gaskets.

---

I'm pretty sure I'm getting closed loop at idle. Here are the tuner pro readings. I've read that -5 is a good reading!

[cosmic_splatter]

Fixkick,

I've read all your pages regarding idle issues on a 16v engine. I'm still trying to resolve the issue with my idle. It seems very inconsistent. Like something sticking or intermittently not closing etc.

I noticed that the idle will drop occasionally when it is hot outside and the engine is in the warm up stages or hot. (ie. going lean) . It will sometimes drop to near 200-400 rpm. But, it doesn't seem to do this consistently after the engine is fully hot. However, the engine will idle rough occasionally with a slight bounce on the mounts.

My number one suspect is the EGR Main valve. Since opening that port on the intake to resolve the 51 error, it seems like that circuit is now exposed to outside air where it wasn't before. My idle seemed fine prior to fixing that issue. Additionally, the idle seemed fine when the car was started right after the repairs, but the issues started after the first test drive. Strange. (EGR kicking in on test drive?)

I know you pro mechanics hate throwing parts at an issue, but sometimes it's just easier for us hacks to change the parts and see if the symptom changes. I don't mind since I want to have the spare parts on hand since I will be using the vehicle on an island where parts aren't available and shipping one part in would equal the cost of buying all spare parts while in the USA. Thus, I purchased a new EGR valve, a used Idle speed control as well as a used throttle body assembly.

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.

thanks again for your help!

John