WHAT THE F%&#!!!

#11

"Shades" <shades_1970(at)netins(dot)net> wrote

Quote:

Gaskets done.
----------

Hmmmm... dam.

Take the IAC out (Idle Air Control, on the back of the TBI with a 4 wire connection), and gently wiggle
the plunger as far back as it'll go. Take the truck out on the road, get her warmed up and stay over 30mph
for about 5 miles. That will reset the IAC.

I figure it's pulling air in somewhere.. vac hose most likely. But it's possible you got another bad IAC
if you already replaced it.

Real stumper for sure.

Check list:

Fuel press.
Fuel press reg inside the TBI (Spring, gaskets, and "membrane")
TBI gaskets.
Vac hoses
PCV
Air pump check valves (if equipped)
IAC

Gremlins (Hard to find/kill)

HDS

#12

Gone through 2 used IAC valves and one new. All doing the same thing. There
is a wrong signal originating from somewhere that is telling the IAC valve
to fully open. There is no black smoke at any time, so its not flooding in
any way.

Like the follow up post I did(in this thread) said, after the
overheating incident, now 75% of the time it is idling right at all
temps(still not starting exactly right but acceptable, 1000-1200 at first
start and 700RPM warmed up). Before the overheating, it was idling wrong
100% of the time(HARD starting, 600-800RPM first started and 1200RPM warmed
up).

"HDS" <None (AT) None (DOT) com> wrote

Quote:

"Shades" <shades_1970(at)netins(dot)net> wrote in message
news:mrOdnXc9LeK5OUTenZ2dnUVZ_sqdnZ2d (AT) rapidnet (DOT) com...
Gaskets done.
----------

Hmmmm... dam.

Take the IAC out (Idle Air Control, on the back of the TBI with a 4 wire
connection), and gently wiggle
the plunger as far back as it'll go. Take the truck out on the road, get
her warmed up and stay over 30mph
for about 5 miles. That will reset the IAC.

I figure it's pulling air in somewhere.. vac hose most likely. But it's
possible you got another bad IAC
if you already replaced it.

Real stumper for sure.

Check list:

Fuel press.
Fuel press reg inside the TBI (Spring, gaskets, and "membrane")
TBI gaskets.
Vac hoses
PCV
Air pump check valves (if equipped)
IAC

Gremlins (Hard to find/kill)

HDS

#13

Shades, I agree that you could have an air leak. Check the throttle
shaft in theTBI for slop. If the bushings or shaft are worn, you could
get air leakage and/or the TPS could send out a false signal (I've only
seen it twice but it does happen)

Quote:

Group: alt.autos.4x4.chevy-trucks Date: Wed,
Jan 25, 2006, 12:44pm (EST-1) From:
shades_1970netinsnet (Shades)
OK, I have been having the high idle problem
for months now, replacing nearly everything
related to the TBI system. Thanx to everyone
for their input,

%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
"So why do I drive a big SUV? It's because I have to haul numerous
people and things to places."
~ R. Lee Baxton ~

#14

The throttle shaft is as tight as any I have felt.

"Rich B" <AutoHobbyist (AT) webtv (DOT) net> wrote in message

Quote:

Check the throttle shaft in theTBI for slop. If the bushings or shaft
are worn, you could
get air leakage and/or the TPS could send out a false signal

#15

"Shades" <shades_1970(at)netins(dot)net> wrote

Quote:

OK, I have been having the high idle problem for months now, replacing
nearly everything related to the TBI system. Thanx to everyone for their
input, BTW!

Yesterday the idler pulley crapped out while I was hooking up my
trailer and it overheated(temp gauge was pegged well over the 260 on the
gauge). Nothing I could do to cool it off so I just shut it off. After a
couple errands in our other vehicle, I went and got a new idler($17.40 or
so), removed the old(plastic) and installed the new(stamped steel), the
belt was good so I reused it(though routing was interesting with no
diagram(third time was a charm)). Only lost about a quart and a half of
coolant.

Started it up(same as before, needed the throttle cracked), let it run
a bit, then drove it home...

NOW, THIS is where it gets interesting... Pulled up in front of my house
and something was different...it was idling at 700RPM! Switched it to an
AC setting and it went to about 850-900RPM! Went out this morning to start
some running and it started first try with no throttle, went to 1000RPM
then 1100RPM, then down to 700RPM after it warmed up! Started and shut off
4-5 times with no starting or idle problems(went to 8-900 and dropped
right down to 700)!

WHAT THE F%&#????

Any ideas on this new tidbit, anyone? Everyone?

I don't know if this applies to your situation, but I had a similar problem
with a dodge 600 4 banger.
It had similar problems. high idle, hard starting.

It had a bad head gasket, combustion gas leaking into the coolant, forcing
coolant out of rad until the termostat opened.

After I repaced the head gasket, all the problems went away including the
high idle!

Maybe the overheating caused the gasket to "seal up".
Try checking the compression.

hope this helps!

#16

--
Remove "pants" to email
"Chris" <doomroom (AT) pants (DOT) mts.net> wrote

Quote:

"Shades" <shades_1970(at)netins(dot)net> wrote in message
news:5tednd9RmruXWkreRVn-qA (AT) rapidnet (DOT) com...
OK, I have been having the high idle problem for months now, replacing
nearly everything related to the TBI system. Thanx to everyone for their
input, BTW!

Yesterday the idler pulley crapped out while I was hooking up my
trailer and it overheated(temp gauge was pegged well over the 260 on the
gauge). Nothing I could do to cool it off so I just shut it off. After a
couple errands in our other vehicle, I went and got a new idler($17.40 or
so), removed the old(plastic) and installed the new(stamped steel), the
belt was good so I reused it(though routing was interesting with no
diagram(third time was a charm)). Only lost about a quart and a half of
coolant.

Started it up(same as before, needed the throttle cracked), let it run
a bit, then drove it home...

NOW, THIS is where it gets interesting... Pulled up in front of my house
and something was different...it was idling at 700RPM! Switched it to an
AC setting and it went to about 850-900RPM! Went out this morning to
start some running and it started first try with no throttle, went to
1000RPM then 1100RPM, then down to 700RPM after it warmed up! Started and
shut off 4-5 times with no starting or idle problems(went to 8-900 and
dropped right down to 700)!

WHAT THE F%&#????

Any ideas on this new tidbit, anyone? Everyone?

I don't know if this applies to your situation, but I had a similar
problem with a dodge 600 4 banger.
It had similar problems. high idle, hard starting.

It had a bad head gasket, combustion gas leaking into the coolant, forcing
coolant out of rad until the termostat opened.

After I repaced the head gasket, all the problems went away including the
high idle!

Maybe the overheating caused the gasket to "seal up".
Try checking the compression.

hope this helps!

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WHAT THE F%&#!!!

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