ApacheDrill

iTrader: (21)

My car starts fine then after i have driven for awile will not restart without using the gas in the start cycle. Never had this problem before and its only when the engine is warm????????Anyone ever had this happen? Im lost.. <img border="0" alt="[Banging Head]" title="" src="graemlins/gr_banghead.gif" />

VSGLS1

iTrader: (8)

What do you have done to your car??? I have a Hotcam and my car will not idle after a warm startup. I have to play with the gas pedal for about 20 seconds then it will idle fine...

Casper9T9

iTrader: (1)

My dad's 99 GMC Sierra is doing the same thing, and we can't find out what is wrong. It has a new fuel filter, and the pump is working fine. I'm at a loss.

Midnight F-117A

something's wrong with the IAC (Idle Air Control)

ApacheDrill

iTrader: (21)

I did change my headers out and this started a few days after and threw a code. Not sure what code it is, but it had shorties, i changes to mid length headers. Runs great when started just hesitates intially until the throatle is pushed in all they way then fires. I have a Hypertec Programer. Changing out my headers should have not required me to re program. I also am no longer running catalitic converters, not sure this makes a difference. Just kinda enbarising to have a hot rod thats a rocket and doest start on the first turn. <img border="0" alt="[bullshit]" title="" src="graemlins/gr_bs.gif" />

strokedls1

iTrader: (1)

Doing the throttle body coolant bypass helped my car idle at on hot start up conditions. Before I did it I always had problems with it.

jimmyblue

iTrader: (11)

One guess: maybe you have some fuel injector
leakage, that requires more air to start
when hot than you can get through the bleed
hole in the throttle plate.

Messing with the throttle while trying to start
only confuses the computer and makes it impossible
for it to learn anything. Modern EFI cars should
start with no pedal. Full pedal is often a
"clearing signal" for a flooded condition,
invoking a special start mode, but I don't
know if this is the case on the LS-1. The IAC
position is set by learning, the more you
help it, the less it learns.

A "vapor lock" condition is another possibility.
The "dead end" fuel rails on this motor could
potentially build a gasoline vapor bubble when
hot, that will clear only after many injector
cycles. A TPS position above idle might cause
more injector duty cycle and clear things
faster. Then again, TPS position might also
take you off the canned idle settings and
onto normal throttle program, changing fuel
and spark.

Removing fuel rail insulation, running headers
instead of stock manifolds, even fuel rail
covers can all potentially change the amount of
heat seen by the fuel rails, how long it takes
to get them hot vs. the natural engine bay
cooldown cycle, etc. If you wanted to test this,
try opening the hood and blowing some shop air,
or wetting down the fuel rails carefully so that
they get cool but the rest of the engine doesn't.

IAT sensor could be getting pretty warm, telling
the PCM to retard timing. If you have a setup
where the IAT sensor isn't in the true airstream,
it could be sending a way-hot inlet air temp
reading. Easy starting comes with more spark
advance (to a point; too much can result in
an engine "fighting itself", firing ahead of
maximum low-RPM power contribution. Are you
tricking timing?

I would recommend that you give it another
chance to learn how to start properly (with
a battery charger handy, in case it's a slow
learner) and keep your foot off the pedal.
Take your time, keep trying, and see if it
wises up.