I have a 04 Chevy Express 3500 V8 6.0 Cut away chassis School bus ( short bus or shuttle size )
I can see it's got CABLE throttle on my throttle body. Just M2C . 😉
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I looked up the 6.0 engine again and they clearly state that the cable controlled throttle was kept through 2006. Anyhow I see on google that Delphi is suppose to be the OE manufacturer for this part, IAC on that engine. Not cheap, $115. My question: Is there a way to test with an ohm meter the valve motor? I was checking and read some where that the two outer pins on the 4 pin connector has like 40 ohms and the two inside ones had 20 ohms...but not sure.
If anyone knows what these pins should be in relationship to the motor let me know.

 

I disconnected the battery over night and then re-installed the IAC. It is a pain to put back in as one of the screws is behind the valve body and it hard to get to. Anyhow after putting everything back, I started it and it seemed to not have that fast idle issue. The temp of the engine showed 104 degree F. I took it for a drive and it seemed to run fine but the idle speed ranges between 475 and 520. I think I may have a TPS issue but not sure. Those are cheap and easy to replace. I also cleaned the MAF as it looked dirty. I did use the proper fluid to clean it with. Anyhow I guess I need to look for any vacuum leaks.
I did not get any codes. I do have a OBDII scanner tool but did not do a real time look at fuel trims or anything else. It drives fine and has good power and acceleration. I just hate to take it to a shop as I am retired on a fixed income and have to do most the work myself. This is an RV so pulling a heavy box on the back of the 3500 van give the motor a good work out. Have taken this across the USA and never had a problem going up hills or anything.
Thanks for the help

 

The short trim and long trim are within specs. The 2nd bank has a bit higher % on the long trim than the bank 1 but overall I do not get any codes. I did find that someone had used JB weld on a part of the bank 2 exhaust manifold where it meets the head. I bought some sealant like JB but is designed for 1000 degree application. I cleaned off the JB stuff and applied this sealant.
The idle when cold still does not run at 1500 rpm like it should but it does idle around 500 rpm until it reaches operating temp and closed loop. I think it probably does need a new IAC but they are not cheap and only work when the engine is cold. After that the engine runs normally. This is not an electronic throttle body.
I was not able to find any vacuum leaks looking and using a can of carb cleaner. The only thing I did not do is spray some cleaner into the PVC valve that is part of the drivers side valve cover. Stupid design.

 

IAC RESET: ignition ON 10 sec, OFF 5 sec, START
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2003 Chevrolet Express 3500 Cargo Van; LQ4 6.0L V8

 

The fact is what I physically saw and experienced. I had to remove the throttle body to change the air control valve, as the screws were impossible to access. The throttle body has both the cable to the pedal and the cable for the transmission. It also has water hoses at the bottom rear for heating the throttle body. I also replaced the TPS while I was doing all this. I did take it for a long drive, but it still idles at around 500 rpm and when it is cold it still does not always start the idle at around 1500 rpm and then slow down after a few seconds like it once did. I was looking at my O2 sensors on my scan tool and short trim and long trim one of the banks that seems out of specs so I am investigating that. It maybe that I have a O2 sensor after the CAT that is bad...just have to look further. Never get any codes so it makes it tough to analyze.

 

I ran my scan tool again and the trim values for both banks are about the same along with the O2 sensor voltages. I think all of that is OK. The only other thing I have not tried is removing the battery voltage and letting it sit for awhile after removing any residual voltage in the computer.
I just hate having to run a relearn process for smog testing here in CA. but I guess that will have to be done.
Once the engine is fully warmed up it runs fine out on the road.
It just bugs me that it does not trigger the Air Idle Control to let it start at 1500 rpms.
Any ideas will be helpful but Please note that this is not a Throttle body that is all electronic. It is one that uses a cable. The RV on a Chevy 2005 6.0 engine is how it came.

 

Interesting observation. When I thought the AIC was not working it was in the mid 60 F temp outside. This morning is was down into the low 50 F outside temp and the engine started running at around 1500 RPM and then dropped down to about 700. When it finally got to normal temp of 190 degrees F it was idling at around 500. I think that is too low but when in gear it does not stall. I may adjust the idle stop on the throttle body a bit.
Conclusion is that something in the computer is able to sense the outside temp. and then sets the AIC to allow more air in to start the engine at a faster idle than normal.
Not sure how it is doing that. Anyone have an idea?