91 8V hard start long cranking on hot soak. cold great

[barnbiketom]

cold start perfect.
hot soak long cranking. kinda flood? smell gas too. I got the "Standard" TBI rebuild kit.gaskts o-rings etc.
also it idles at 1200...always did for 2 years maaybe /iac
I wonder if the injector rings are leeking? injector? going to do a visual before
I tear it apart.

[fixkick]

WELCOME !
Speed Density systems. (assuming good spark parts , tuneup parts good)
91 is easy to see injector leaks, key on 3 times no start, look at injector, no leaks, it's ok. (in that department)
1200, is wrong HOT there is a problem there.

Cold start , or any really , are all temp sensor based , for fueling. (tables)
i'd check the ECT first with an ohm meter.
i'd need outdoor temps, but lets do examples. pretend freezing day, in drive way parked.
32F (0c) i unplug it and it reads, 6000 ohms,(about) if more, the ECU thinks you are in Siberia and it will flood, check hot for 300 ohms to (both temp ends)
http://www.fixkick.com/ECU/temp-sensors.html
check IAT too.... on 8v its very important sensor.... same rules but is air temp not water. the IAT is a faster acting ECT.

flooding has many causes. too high fuel pressure tops list. 30psi is ok 60 not.
1200 hot? is bad, cold is normal until the IAC (thermal ) closes.
1200 HOT (is the ECU fast Idle pins stuck true state (a/c, and p/s?)
is the dash pot retracted, ? after start, after 5 to 20 seconds from start it must retract,
is the idle stop screw still at factory spec, TV valve closed 99.9% (.0005 gap in bore to plate) if the TV passes water past the plate (test) the valve is set wrong.
grimlins did that.

the 8v loves to race hot, with any air leaks, it RACES, finding them all is a small horror. for sure the idle speed controls are out of control. (servo loop dead)
and does prefect air fuel mixture, at all times.with leaks of air. Unlike the MPI G16B (leaking)

there are only 3 paths. to leak air. (photo below) (IAC + ISC + Bleed) no others!. (assumes all hoses good and gaskets sure) DP retracted !

here is my drawing off my TBI slide show.
TV is closed, it don't leak. (throttle Valve = TV)
IAC i closed above 150F water temp, if not the engine will scream hot.
the ISC is ECU totally controlled, unplug it, does the idle drop? to 400?
Pinch the ISC air hose, does idle go to 400 or 500 and nearly stall or stall? (all normal) if not you have leaks. VACUUM AIR LEAKS.
The last air leaks is the bleed screw, so screw it in , and bottom it out, (gently) this can cause the ISC to wake up. (as you screw it in)
once all leaks are gone (air) we then set the bleed screw, for 50% duty cycle and the ECU then keeps hot RPM at 800 all the time. (until a/c on or P/s over load.)




and frame 37 here. TBI xray view , is that not good ?
http://www.fixkick.com/fresh-air/Slide_S...ge_37.html

blocking the IAC ports to test it is no fun, its tricky
im idea of testing IAC is like frame 12 shows.
here
http://www.fixkick.com/fresh-air/Slide_S...ge_12.html

this port must not suck air, hot , over, 150f it is closed.
and if the water pipe is clogged it fails. hot water (AF coolant) must flow here.

frame 24 shows clogged up TV. causing fast idle if TV sticks open as does any of 3 throttle cables set tight not lose spec.
Throttle, A/T kickdown and cruise cables all 3 must be slack .

easy check 1.
keys in pocket.
off air tube. top
look at TV
grab DP rod and retract it by hand
the TV must be 99.9% closed, if not that be wrong. fix this first.

[barnbiketom]

Here's my PLAN. i haven't touched it YET...work + weather + laziness but I have the Standard Gasket -0ring kit!!!
1. check ohms on coolant AND intake air sensors just to be sure not skewed (no check engine lite but...)
2. visually check injector after 3 key on engine off cycles for drippages lol
3. make sure DP is retracting, then throttle plate is CLOSED 99.9% (throttle cable OR PO butchery)
4. tear off TBI, see if gaskets are sucked in?? and check IAC water lines for pluggage, then test IAC HOT
closed????? probably in hot water or oven!! I see it hard to use the clay when running, hot haha
but maybe plug with silicone plug on stick?
I have some powder coating plugs maybe I can make fit!!
I used to have a GM TBI plug that you stuck into similar port to check..
5 if that is all ok, renewed etc.. can i check duty cycle of IAC/air bleed ADJUSTMENT with a meter?? 6 VDC??
I'm not sure i have a meter?? DWELL meter??? hmmm
how do you set the duty cycle to 50%

[fixkick]

Here's my PLAN. i haven't touched it YET...work + weather + laziness but I have the Standard Gasket -0ring kit!!!
yes and vacation is first. im in south america. yah!


1. check ohms on coolant AND intake air sensors just to be sure not skewed (no check engine lite but...) ecu can only see open ECt OR SHORTED.
I can't see way off calibration, biased wrong. eg. 150f reads 180 or 180 reads 150F. it is clueless , like lemmings off the cliff


2. visually check injector after 3 key on engine off cycles for drippages lol usually its the o-rings that crack and drip this old.
3. make sure DP is retracting, then throttle plate is CLOSED 99.9% (throttle cable OR PO butchery)
4. tear off TBI, see if gaskets are sucked in?? and check IAC water lines for pluggage, then test IAC HOT
closed????? probably in hot water or oven!! I see it hard to use the clay when running, hot haha
but maybe plug with silicone plug on stick?
I have some powder coating plugs maybe I can make fit!!
I used to have a GM TBI plug that you stuck into similar port to check..
the iac , ways and means, it can be looked at but the screws (3 on side love to stick) and the clay trick or pan of hot water, trick,



5 if that is all ok, renewed etc.. can i check duty cycle of IAC/air bleed ADJUSTMENT with a meter?? 6 VDC??
I'm not sure i have a meter?? DWELL meter??? hmmm
how do you set the duty cycle to 50%

if lucky a DC voltmeter will average the 200 HZ pulses to 1/2 of 14.7vdc running,1/2 battery volts.
some meters are blind to 200 hz. or dead, or just read wrong. (if its a fast sampling DMM it has a great chance of reading 7vdc.
it id looks ok, set the bleed to 7v,
if you have a huge air leak, you turn the bleed and cant get 7v you get 14v because the ECU seens say 1200 rpm hot, and ISC is fully closed and
it can close more, locks there or hunt the throttle. (some do , some dont, base on what firmware is running)
there are DMM with duty meter mode.
and all scopes do this easy.

a normal engine has no air leaks
so the ISC has full control at all times
then you (or factory) SET the bleed to 50% 7vdc average of this A.C square wave.
this means , now the isC IS IN the middle of its range. and can lower idle say 400 rpm (50% less air)or raise it about that or 50% more air.

when you see crazy highHOT RPM's that means the ISC has lost control or ecu is limphome or backup mode.

you locking good. on track

good luck.

[barnbiketom]

W E L L...still 12-1500
Tore into it and found:
Factory TV screw is GOOD un touched ,, still white paint.. TV is closed and dashpot working..??
air bleed screw WAS ALL THE WAY IN.... previous owner had hi idle problem.???
left it still in all the way. keep reading>>>
gaskets all GOOD. injector O-rings all GOOD?? replaced em anyway. haven't tried hot soak yet..
I found the IAC CLOSED when I tore it apart. it was still hot>>>>
I blew thru it.. it was sealed. but I also screwed in the adjustment one turn just in case...
also water lines clear..
ISC..seems to be working BUT when you unplug it.. idle settles to 1000.. plugged in, it goes to 12-1500
I replaced a couple suspect hoses, and propane checked it, sprayed carb cleaner all over and under .. etc.. can't find any vacuum leaks..
??? ???@$@#%??

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no check engine light either, bulb tests ok.. it lights up engine off key on...

[fixkick]

you have air leaks. for sure.
where takes hard work.
Isc (electric) is on right side of TB
THE IAC thermal is in base of TB.

the iSC has and end screw. (factory set for gentle close)
THE IAC adjustment is very very hard reach in the base. under that 3 screw cover.
the ISC has spring and is always closed, with no power, or plugged.
the Iac only closes above 150F.

the IAC can not be removed, So how did you prove its closed? the clay trick>? (OR off those tiny screws on cover?)

I will assume isc and iac are closed, and the TV and the bleed (PO gave up) are all closed
so will say you have a leak , in the intake or some other TB Hidden link,
pinced all hoses.?
PCV hose cracked.?
brake booster hose removed and plugged?
what else>? map hose cracked.?
3 speed vacuum line to its modulator cracked? or mod itself cracked in inside, if 3 speed, pinch hose in 1min flat. idle not drop.?

EGR main BASE GASKET CRACKED.
egr main body cracked,.
egr main guide pin worn so bad it sucks air?


by the process of elimination, we find this
one guy, all ways were checked and we found the TB HAD FREEZE DAMAGE IN SIDE, WERE no man can see. (behind IAC guts)
this was found by making a special TB base gasket, that blocks off holes. (normally open) see my slide show for the 3/8" hole.
also he mid Tb GASKET CAN CRACK AND SUCK IN AND RENDER THE BLEED USELESS.

[barnbiketom]

all gaskets replaced, but old were good...
still 12-1500...
With ISC unplugged AND air line clamped off just to be sure....I removed the water valve cover (3 screws trianglular) started the engine (VEVVED LOL) and stuck my finger into the port on the side. the car slowed down to.. 1200

I've clamped all the vacuum lines i can find.dashpot is pulling off ..sprayed ether all over.. GRRR.

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when i had throttle body off, IAC (thermal) was still hot and plunger was out. I blew thru what I thought was the ports. BUT
just now I started the car, with the IAC cover off I plugged the port with my finger.. it is on the right side looking in from the front??.. car slowed down.. to 1200 haha. GRR
I'm going back to look more.

[fixkick]

remove tb
remove gasket
make test gasket
block the big hole here. IAC bleed
there are 5 small holes that must always be blocked, (called drillings)
then the slot must be filled. and blocked
we see if engine stalls. it must stall. there is no air now. for sure.
it will tack right foot to get it to start at all (press right foot say 5 degrees?
if it stalls, cut the IAC bleed hole back but not slot hole.
if it still stalls, cut the slot hole, bam? 1200 rpm:"
if yes the slot is leaking some way
do not block H2O

clean and new.
http://www.fixkick.com/fresh-air/Slide_S...ge_20.html


freshly off

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those 5 hole small are drilling, and must never be open.
they drill these for the internal system and a gasket is way cheaper that lead plugs. (lazy bums, lol)

[barnbiketom]

ok.. well if I BLOCK THE MAP sensor line.. the car almost stalls.. the hose is good all the way??
but with no map input maybe that will do that too??
any way to check the map output?

[fixkick]

it must be inspected, blocking the MAP , will cause limphone, instantly.
the map is easy to test. first for leaks then volts, i have a map test page.
but its working, im sure, only hose leaks are at issue on it.


this is easy to find, you have all air shut off, and it runs
that impossible or you have leaks, yes you, do....
where? we just block holes and find it , id bet one of those 2 holes in the TB leak, no?
if all gaskets are good. and the brake booster dont leak , where else is there, non?
the engine must no run with all air cut.

if the tb tests fail, then we only need to find the internal part that is bad,

you have a huge air leak.