LS1's idle is too slow

[Big Bodie]

I've been beating my head against the wall on this problem. Here's what I know so far ............. starting up the LS1, it idles way too slow below 300 rpms. Took out the IAC (idle air control) and it's too far out, pushed it back in to stop. Turned key to on and rubber cap goes out about 1/4" and stops. Pushed rubber all the way back in before reinstalling it. Put back on engine, startup and idles great, about 500 rpms. Kill engine, wait 10 sec. and restart, back to old slow problem. Take back out IAC and push bubber cap all the way in. Turn key to on and rubber goes out 1/4" and stops, turn key off wait 10 sec. turn key to on rubber goes out 1/2"more, which closes off the IAC hole to allow the engine to idle faster, like it's choking the engine down ( and sounds like it too). Replaced the IAC with new one and it does same thing, down the drain $90.00. Anyone have any sugestions or fixes ??? The problem does not effect anything at fast speeds.

[Z06 S10]

adjust the idle screw?

[Big Bodie]

Reply to Z06 S10, that's the old way of doing things. The IAC is controlled by the computer and it helps when the A/C is turned on while idleing, etc. Turning the idle screw doesn't do anything for the over rich condition. There's something else that wrong, all the sensors are connected. Thanks anyway.

[farmtruc]

Hey, i don't see your sig, so let's start from the beginning.

What are you mods?
When did this problem start? Was is doing it before or after you installed a part?
Have you removed anything? Added anything? Has anything changed?

Just trying to get an idea here,

maybe all of us can get this fixed.

Also, the iac is a pita, if it's been removed or messed with it'll need to perform kind of a relearn, go drive your truck and do some stop and go and cycle the ignition a few times, if you did already, oh well, we'll see what's on the list to check next.

allen

[GMCwantsLS1]

You might try to reset the PCM by disconnecting the battery for about 10 minuets, then let the PCM relearn everything.

[Hit Man X]

Originally posted by GMCwantsLS1@Jan 14 2004, 05:25 PM
You might try to reset the PCM by disconnecting the battery for about 10 minuets, then let the PCM relearn everything.

Try to get everything back to normal then reset it all.

Is your TPS off?

[Big Bodie]

Allen........ No codes, No Check engine light, what I'm trying to find out is what determines where the IAC should be, I know it's controlled by the computer, but what are the factors that move the IAC in or out ???? & I agree it is a PITA.
As for mod's........ headers and that's about it, all the EEC (Electronic Emissions Controls) are hooked up, as are the sensors. The engine is installed in a 90 Chevy truck (w/4l60E) and it will run with the big boys. It's great off idle and very strong.
I'll try what you said about make'n the computer re-learn the new part, I'll let you know. By the way we now have a scanner and I want to put some pic's on here, what the procedure for doing so.

[Bandit]

DO you have access to a scanner? Knowing IAC percentage (or steps/counts), TPS, short term fuel trim, long term fuel trim, and mass airflow readings would help a lot. IAC position is a learned value, and relies heavily on MAF Pushing it in and reinstalling it only makes it worse. Try what GMCWANTSLS1 said, but make sure you do it with a cold engine. Let us know the scanner info if you have it.



Bandit!

[honkydaddy]

May be the idle screw if someone screwed with it because of a vacumm leak.You can check the TPS with a multimeter.

[Hit Man X]

just though of this... are your MAF wires dirty? My F-150 would idle poorly when they were...