I am currently trying to get the car ready for smog and the high idle issue is still there. I'll describe below any information that a part has been replaced or modified.

- The hose that connects from the inter-cooler to the throttle body has been replaced less than a month ago.
- Idle Control Valve is about 2-3 years old
- The car has damage from 1st or 2nd owner in the front where the frame, inter-cooler and radiator is still intact but bent out of its original place.
- Exhaust gaskets has been replaced since last winter.
- Throttle valve cable has been adjusted to the proper tension.
- Exhaust pipe is not original and lacks resonator and a extra muffler with a diameter of 2.5"

This is a 2001 Volvo S40 1.9T iPD

Problem: High Idle code for the check engine light.

Symptoms: Everything idles normally when driving until the vehicle is parked . Idles normally then randomly spikes up to 1,200 peak RPM then slowly dies down to normal idle speed.

Thank you to whomever replies.

 

Have you tried cleaning the MAF sensor with MAF cleaner spray?

 

I might have done that a long while ago and I'll give it another go. If it does not work do you have any ideas on a direction where it could be?

 

My first thought was MAF due to the randomness. My next thought was a small vacuum leak messing with the ECM. I would hook up a DiCE tool and check the IAC counts when this idle up occurs. If the IAC is moving open (IAC counts go up) to cause the idle up then I would think of a bad sensor input. If the IAC is moving closed (IAC counts go down) then maybe a small vacuum leak.

Now one crazy question. How are your motor mounts? Why? Because if the engine is moving too much it may be pulling on something that it shouldn't. Does the car vibrate excessively in gear with your foot on the brake? Any bumping under acceleration?

 

Not much vibration but a metal rattling noise roughly at 1,750-1,900 RPM but not a big deal but if I give it a good punch on the gas the car may resonate for a second or two when trying to build boost but not much and the engine dose not bump or vibrate excessively.

But I not only cleaned the MAF but also the Throttle Body Inner Housing and Butterfly Valve edges, the high idle is back and it's not dying down. Do you think its a leaky Throttle Valve?

I'll give a pin test with a volt meter to the IAC valve and look at the CenTech OBDII Automotive reader to look at the live data. Since I am a college student and a Mechatronic Student as well; I like to do it right and cheap.

Lastly I will provide Pictures of the Motor mounts and anything else to get a good look at what I'm seeing (or a video if you need to look and hear at anything!)

 

So looking around YouTube I looked at a couple of IAC in class automotive shop that showed me how the IAC and they recommend another video to look at and figured I give it a go. turned out that WAS the problem with my car! WHO KNEW!

Someone moved the base screw further out than its original position which made the idle higher than usual.

All I need to know is what do you recommend to hold the base screw, what is the expected minimum idle speed and how to adjust it properly?

Thanks to whom ever replies!

Here is the link to the video; I found it helpful with my situation!

 

Passed Smog without any hiccups.