VIN: 1GCHG35U231110297

I am getting word that my van is a transition model and the engine may be a throw back that was from another truck line, that GMC wanted to use up, and the throttle bodies used are a mix of cable or e-throttle body types. It seems no one has a way of discerning between the engine and throttle body I have to zero in on a IAC.

The IACs all look alike except for the orientation of the connector. All but Delphi provide zero specs.
My two best prospects are the SMP #AC234, you mention, and Delphi #CV10017.
But the manufacturers do no claim fitment and I can not get compatibility of engine and throttle body across multiple vendors.
It looks like I will need to buy one and try it ... which against my grain.

 

I was beginning to think this could be a transition-related issue but it’s hard to verify which ones that applies to.

Unfortunately the only part #’s I could come up with are for the throttle body assembly - nothing specific to the IAC.

GM # 12596575
AC Delhi # 2171572

Based on my experience with GM vehicles of this era (at least 1/2 my customers drive GM vehicles and one of them has a fleet of express van cutaways) I really don’t think there’s reason to be concerned about the replacement, even if it doesn’t look like an exact match from the pictures. The SMP or the Delphi should work without issue.

You could also take it to the parts store with you to compare.

 

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The part numbers you found are the ones I started with ... that are discontinued, and yes - no separate IAC #.
Are any of the vehicles you work on a '03 Express 3500 with a throttle body that looks like the below?
Or do any of the vehicles you work on have a throttle body that looks like the below?
Note the vacuum hose at the top left. It seems to be a precursor to the Cardone 67-1075, also pictured below.




But the Cardone 67-1014, below, looks more like what I have in my van.
What is jamming me up is that RockAuto has different IACs for those two throttle bodies, both for an LQ4 6.0L V8. The only difference I can see is the integrated vacuum line connection.





?????

 

Addendum:
Cardone 67-1075, has a 100mm air inlet
Cardone 67-1014, has a 94mm air inlet.

 

Summit racing lets you search by make/engine not just make/model. Also they tend to have knowledgeable people that answer the phone and people that know enough to do engine swaps in the reviews. https://www.summitracing.com/parts/s...make/chevrolet

Personally I have no idea but it worked for Larry.

"LARRY · 4 years ago Fixed my problem
several sites said this part didn't fit my van. yes it works perfectly in my 2003 Chevrolet Express 2500. it now starts instantly and idles smoothly"

 

Wow you may have just pulled my fat out of the fire.
May have ...
What size engine are you running? Is there a 'U' in the 8th place of your VIN?
Do you have info on your throttle body?

The Summit sales staff immediately found an SMP: AC147T. They are not clear on what the T added to the AC147 is for.
It is reported to fit the engine of a 2500 6.0L V8 w/ 'U' in the VIN which is the same LQ4 as my 3500. But the 3500, in their file does not have the 'U'.
I think I got that straight.

Now looking at the part on the SMP website it fits a "Chevrolet Express 3500 (02-96)".
GM Tech support indicates the vehicle is a 2002 build.

On Rockauto a 2002 Express - 2500 6.0L V8 does not exist, but a 6.0L V8 in a Silverado does. The IACs for the Silverado are different than SMP AC147.
This is where I lose my mind

It all seems to boil down to a throttle body with a 94mm air inlet w/o an integrated vacuum line or 100mm air inlet w/ an integrated vacuum line. They both identify different IACs,

What is the horrific disconnect about?
I can't believe GM decided to make an entire air fuel intake for ONE year for an existing engine type.
What is in the 2003 Express 3500 has to have come out of another truck, doesn't it?

 

The “T” is a designation for SMP’s “T series” line of parts.

I don’t know what the differences are between them (if there’s a difference at all) because if you look at stock pics of AC147 vs. AC147T they look exactly the same but the T series is cheaper. The same goes for any SMP part that has a T designation.

Even the IAC I suggested - AC234 - has a “T” series counterpart and the photos don’t show any differences between them.

As to the differences in the throttle bodies (specifically the integrated vs. non-integrated vacuum line) - design changes like this happen all the time and there’s several reasons for it which are typically only known to the manufacturer (this kind of thing happens with all makes) but have little or no impact on engine performance. In regards to IAC functionality, there wouldn’t be any noticeable difference in idle quality between these 2 TB’s.

I haven’t been able to find any more specific information about the IAC part number, but my advice hasn’t changed either - any IAC that’s physically identical in size and nose-cone shape to the one you removed will work, because they all work the same.

I forgot about this, but here’s a write up I did about the older style IAC’s - IAC Valve Guts - keep in mind the IAC on your van works exactly the same as the old style IAC even though it looks different.

 

I went from knowing nothing about this to knowing more than I ever wanted to know. So take my Qs as knowing enough to be dangerous but not enough to know I know.

" ... AC147 vs. AC147T they look exactly the same but the T series is cheaper ..." I think you are on it. The 'T' has a 12 month warranty while without it there is a 36 month warranty.

"... any IAC that’s physically identical in size and nose-cone shape ..." ? So far the only IAC with dimensions of any kind was Delphi. Am I looking in the wrong places?
It was an effort to find a 7mm air inlet difference in the Cardone 67-1014 and 67-1075 Throttle Bodies which are the replacements for different LQ4 engines.
These two throttle bodies purportedly take different IACs.

"... they all work the same." ? I can understand that IACs work the same in principal but that is not the same for any engine and throttle body is it?
How does IAC timing work? What about PCM control?

 

All IAC valves of this era on GM vehicles are controlled by the PCM in the same way.

When the PCM detects acceleration via the TPS, the IAC is closed and all airflow is directed through the throttle bore.

When the PCM detects deceleration, it opens the IAC to prevent the engine from stalling. Idle speed is then adjusted to compensate for load such as the AC and electrical accessories.

At key off, the PCM closes the IAC fully then opens it slightly to prepare for the next start.

Whether it’s the SMP or Delphi, the PCM will control it in the same way.

I don’t think it’s useful to continue looking at what IAC is being used for other throttle bodies. It’s only confusing the issue further. Focus on the style you have.

I think either the SMP AC234 or Delphi CV10017 will work.

 

I’m driving a 2003 Chevrolet Express 3500 with a Vortec 6000, LQ4 6.0L V8 MFI LS Gen III, 5964cc, 364ci engine.
Yours may have this same fix if your VIN is the same +/- the 9th #. The first 11 VIN are 1GCHG35U231, minus the vehicle serial #. I have gotten feed back that one IAC from my preferred group is for the ’N’ engine.
So you if just want an answer that may apply, or not, jump to the bottom.

First off:
When I got the van used, I downloaded the vehicle specs, from where I do not recall, and it is “supposed” to have an electronic throttle body. But it does not. It has a Drive-By-Cable (DBC) throttle body. There are plenty of 6.0L V8 engines with DBC throttle bodies.

But there is no IAC for my van. The throttle body IAC and TPS are an assembly, that is discontinued.

Second:
Some speculation is that because the 2003 van was a transition year and built in 2002 for ’03 sales, it was likely a mix of parts from other production lines. This mixed Drive-By-Wire (DBW) and a DBC throttle bodies. The DBC being the previously mentioned GM throttle body assembly.

Third:
The Vortec 6000, LQ4 6.0L V8 MFI LS Gen III; 5964cc, 364ci w/ cable operated throttle body is not a new animal. You can find lists of LQ4 applications if you look. So I believed there was an IAC out there. Hell - there is one in the van I need to replace!?

Forth:
Working through interchange #s for the P#20663 over J1702L, Made in Mexico, that was on the IAC removed and the GM P#12596575 (assembly), and from a YouTube P#980-005 reference; I worked my way down to 13 IACs, that fall into 2 groups without any overlap. Except for Delphi there are no dimensions or additional information and when you drill down on parts sites, and manufacturers of the IAC is not for a 2003 Chevy Express 3500, even with the specified engine.

Group One is from the removed IAC:
Delphi CV10017
ACDelco 2171806
SMP AC234
UMP IAC47
IPD 457069
AUTEX 958074
Holley 543-34
FiTech IAC #70050-13

Group Two is from the GM P# and YouTube reference:
Delphi CV10011
SMP AC147
UMP IAC33
Autotechnica GN1317577
Beck Arnley 1591032

Curiously, of the two IACs I believed fit there was only a 0.01” difference in the step motor operation. With something that small I have to wonder how much off the idle could be during warm up and at a stop

Fifth:
Drilling down on throttle bodies, I found an after market manufacture of two throttle bodies for the ’03. The one that comes up in relation to the first group of IACs, does not match the existing throttle body, and does not include an IAC; and the one that comes up with the second group of IACs matches the installed throttle body, and also does not come with an IAC. At this point I could have just bought any IAC and tried it. But the one primary (name) manufacturer of IACs from both groups indicated neither was for a Chevy Express 3500 of any year w/ a 6.0L V8.

Sixth:
I researched engine rebuilds and found a reference to a Holley throttle body that could take the original IAC and TPS. Also in the same article another ‘performance’ throttle body maker, I contacted, saw no reason the IAC in the throttle body they make would not fit the Holley. I contacted Holley tech support and got a warm ‘they know what they are talking about feeling”. Granted, at this point, I had a large back log of knowledge to bounce off what was being told to me.

A Choice:
It would be the Holley 543-34 IAC or the Delphi CV10017. Both have, like many, if not all, of Group One, the orientation of the connector matching the original. Even though the Delphi had a better warranty it was also more expensive. There are all the other choices in Group One but I wanted to support a supplier that was aware of what they were selling and it was still a guess so I took a middle of the road price.

I ordered and installed a Holley 543-34 IAC. I did the reset sequence, and the start-up idle was normal. Reset is 10 sec to ignition On and 5 sec to ignition Off and then to Start.

Conclusion:
At this point I believe that the 2003 Chevy Express 3500 6.L V8 is “supposed to be” a drive-by-wire throttle body not a drive-by-cable. Never mind the GM P# is the entire throttle body assembly, which is drive-by-cable. So aftermarket suppliers don’t know the difference.

What I do not know is why there was a complete dead dash and Start as a prelude to the bad idle. The IAC is just what was in the way of me knowing if something else was happening. Yes I did parasitic drain testing. As of now everything is working.

After The Fact:
So far so good. I have driven out a half dozen times without issue. I never tracked the start-up idle cycle before and now it seems that the new cycle is revving a bit at the start before quickly settling to the warm up idle. I will be curious to see how this might impact mileage.