wpatters1229

I have replaced the idle air intake valve and the TPS. Still, the van idles slowly to the point of almost stalling. Runs better when warm but still low idle.
Maybe it needs to relearn the idle position. This is not an electronic throttle body. 6.0 V8 LZ4 engine.
Any ideas on how to reset the idle positon in the computer?

mountainmanjoe

You need a pretty good diagnostic scan tool for that. Or you can try unhooking the battery, then hold down the brake pedal. That might clear the memory and force it to relearn.

But I would try basic troubleshooting 1st. Replace air filter, measure fuel pressure, check for exhaust restriction, clean the MAF sensor, etc.

wpatters1229

With the non-electronic throttle body, there is not much to find on how to relearn except just driving it. I did notice a small screw and locking nut under the throttle butterfly stop. I was thinking of adjusting that a tiny bit to get the idle to be at the right rpm while in park or drive.

mountainmanjoe

This makes absolutely no sense.
There is no 6.0L LZ4 engine. The LZ4 is a 3.5L engine for small cars (https://en.wikipedia.org/wiki/GM_High_Value_engine#LZ4)

Your van came with an LQ4 engine, which has an electronic throttle. This is confirmed by the GM literature, as well as part catalogs.

Was your engine transplanted from another vehicle or monkeyed with?

wpatters1229

Trust me this is a 2005 chevy express 3500 with a manual throttle body. It is in an RV. Original engine 6.0. I have replaced both devices, TPS and the idle control valve. I think the problem might be the sensor in the intake. Bought some MAP cleaner. Have cleaned it before but has been awhile.

wpatters1229

https://media.gm.ca/dam/Media/docume...05Express.html

mountainmanjoe

There you go. It says 6.0L LQ4 engine with electronic cruise control (no cable).
So either your engine was transplanted or the cut-aways are different.

Anyhow, as far as I know for the IAC valve to work the throttle needs to be shut.
You could also try some fuel system cleaner. If this is the poppet valve style fuel spider assembly then those were problematic too.
Also, the computer will need some time to adjust.

wpatters1229

this is exactly the TB I have except mine does not have the tube in the upper left. Maybe because mine is CA?? https://auto101.net/products/gm-ls-4...s6-lsx-ls-swap

wpatters1229

Express van's started getting the Vortec Gen 3 family of engines in 2003, and stayed with CABLE throttle through 2006. https://www.lt1swap.com/identify_vortec_engine.htm

mountainmanjoe

What's that? You're presenting somebody's home made engine swap website as evidence?