Hello Forum,



I’m back on here looking for some advice regarding a high idle issue I’ve been chasing for almost two years now.



The issue:

When I start the van—cold or warm—the RPMs shoot up to around 2300 and slowly settle down to normal idle speed. Other times, it starts and idles perfectly. It’s completely random.



Sometimes it even feels like cruise control is on… except my van doesn’t have cruise control 😅🤷🏻‍♂️



I removed the throttle body, gave it a deep clean, and installed a brand-new AC-Delco Idle Air Control (IAC) valve and Throttle Position Sensor (TPS). After that, I thought the problem was fixed. I went on a 60-mile test drive and the van ran flawlessly.



But… I shut it off for about 5 minutes, and when I started it again, the high idle issue returned. Then, after shutting it off for another 2-3 minutes and restarting, the idle was back to normal 😩



I’ve sprayed carb cleaner all over the intake and vacuum lines to check for vacuum leaks—no change, and no leaks found.



Other symptoms:

• When the idle is acting up, it revs extremely high in Park or Neutral.
• The moment I shift into gear (Drive or Reverse), the idle drops a bit and smooths out.
• However, it still feels like the throttle is slightly engaged—if I let go of the brake, the van starts rolling on its own.

Background on the van:

• 2004 Chevy van
• 6.0L LQ4
• Cable-driven throttle body
• No cruise control

One headache is that I can’t find an IAC that officially fits this year/model. Anytime I search using my VIN or year/make/model, parts come back as “not compatible.” I’ve been using IAC valves from other GM vehicles that came with the same 6.0L engine.



Right now, the van is actually running the best it has in a while, but this random high idle is driving me nuts.



Any ideas on what could cause intermittent high idle like this?



Thanks in advance for any help or insight you guys can offer!

 

Alright, no need to all rush in at once with help 😅



For anyone reading this later on, I’ll update tomorrow with photos of the part numbers for the Idle air control that worked for my 6.0 LQ4 from 2004 with cable throttle body and the TPS —just in case someone else is dealing with a similar issue.



I believe replacing the Throttle Position Sensor (TPS) finally solved the problem. That said, it took nearly 300 miles of driving before the idle fully leveled out.


After doing some research, I found mixed info:

Some say you need a fancy mechanic’s scanner to reset the TPS, while others claim you just need to drive it between 50–300 miles so the ECU can relearn it—especially with a cable throttle body 🤷🏻‍♂️



For me, things started improving noticeably around the 200-mile mark. I’ve now driven roughly 300 miles, and the idle is perfect.

No more random revving, and startup idle has been consistently solid. I’ve started the van 13 times since the install, each start up I’m scared 😅

• The first 3 were rough (scary high idle)
• The next 5 improved gradually
• And the last 5 have been spot-on

Even the transmission shifts feel smoother now—night and day difference.



Also, fun fact:

Over all the years I’ve owned this van, I’ve only replaced 3 ignition coils. That means 5 of them are still original from 2004… with 342k miles on them 😅



What do you guys think?

Should I replace the remaining coils as preventive maintenance—or let them be?

 

Hello forum,



Just wanted to share the part numbers that worked for my 2004 Chevy Express 3500 6.0L LQ4 with a cable throttle body:

• Idle Air Control (IAC): Delphi CV10012
• Throttle Position Sensor (TPS): ACDelco GM# 88864359

The TPS was easy to source locally—no issues there. However, the IAC was a completely different story. I went through a major mission trying to find one that worked properly… I must’ve ordered at least six different ones before finally landing on the right one.



Hope this saves someone else the headache!

 

The above part number for the IDLE AIR CONTROL is WRONG!!!

i apologize for that…. Even tho the above IAC worked. It wasn’t 100%

here are the correct part number for the IDLE AIR CONTROL…

 

That sounds right for it to need a relearn. I don't know about that van specifically but a lot of other cars I've worked on need a computer relearn after swapping parts of the throttle.

I don't know about the coils. When I bought my van at 185,000 miles I considered swapping the coils when I did the plugs. Most of the research I did suggested that the coils were mostly bulletproof so I left them alone. This actually reminds me that I wanted to buy one ACDelco coil and a plug to keep in the van since I'm on the road a lot.

 

Small list of things all done recently 😅

 

I'd ditch the K&N and replace it with a good paper one. If there is too much oil it can get on the wire on the air flow sensor and cause it to read inaccurately so clean it when you replace the filter.