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2002 Montero sport 3.5V6 with P0506 (after Timing belt and PCV replacement)

Hi everyone,
Miles: 130,000. Bought recently drove home over 2 hour drive no issues, Recent work: Timing belt (preemptive). All Serpentine belts, PCV valve (after timing belt job I noticed oil in exhaust)
It gave a P0506 code and idling at 500 rpm after the timing belt job, found some oil in exhaust. Got the PCV valve replaced. That solved the oil in exhaust issue, but the code has come back. Drives ok, no issues, no smoke.
I am going to clean the throttle body and install new air filter, today and take it on a highway drive (clean oil residue from cat). Any other suggestions or your experience related to this code on this vehicle.
PS: I had the timing belt work done at a very trusted place, but this time their game was not so good. Boss on vacation, new location and their work was somewhat careless not their usual style.

Update:
Checked Air filter, Good, did not replace.
Checked Air intake pipe from filter box to throttle body, no obstructions.
Found throttle cable slack when vehicle idling. Did minimum adjustment to reduce the slack.
Cleaned Throttle body. Took out Idle air control motor, cleaned, verified function and cleaned the cavity it goes into. Reinstalled.
Re assembled every thing. Key on vehicle starts like a dream.

Only issue: Vehicle now idling at around 1200 RPM, left it for 20 minutes, no difference.
Any one know how to adjust the idling RPM on these things.

You don’t adjust the idle - the computer does.

You probably have a vacuum leak - or whatever you did to the throttle cable was a bit too much and you now have the throttle plate open a hair or so.

The number one cause listed in obd-codes.com for this is a vacuum leak. There is supposed to be a little slack in the throttle cable, not much, but some. The number three on the list is a faulty pcv valve.

A low idle speed could also be caused if the timing belt tensioner is not properly adjusted or they are off a tooth.

I can hear a hissing sound when the engine is idling (not in the cabin, but with the hood open and with my ear close to throttle body).
I sure hope they did not screw up the timing belt tensioner. When I got the car back after the timing belt job, they had forgot to check the PCV valve or tighten the serpentine belts. I had to go back and get them to do it.
I have no issues or hesitation when I stab the throttle.
Any quick check for the timing belt being off? Or the tensioner adjusted wrong?

Let’s see:
You probably have a vacuum leak - or whatever you did to the throttle cable was a bit too much and you now have the throttle plate open a hair or so.

 +

I can hear a hissing sound…close to throttle body).

 = 

So did you check for vacuum leaks and check the throttle plate or what?

I started out by just listening. Here are my next tasks.
1- Check throttle plate. Should be closed when idling. Adjust if needed
2- Vacuum leaks. I could not find any leaks, does not mean there are not any. I have changed one obvious looking hose and plan to change out the rest. Good or bad they are 9 years old.
Thanks for your help. After that is done, I am planning to disconnect the battery and let the vehicle learn idle trim again.

Checked the Throttle plate. It is completely closed when the gas pedal is not depressed. There is a very small amount of slack in the cable maybe 1/8".
I replaced some hoses. Had to go and get some more and tomorrow, I will have all the vacuum hoses replaced.
I have noticed something else. The idle with no load is 1200, but once the AC and lights are turned on, it drops to 1000.
Also with the transmission in drive and the car stopped by foot on the brake, the idle stays close to 750. However when the vehicle is in park the idle goes up.
There is some hunting present in the parked idle too. The idle will drop to 1000, then shoot back to 1500 and settle at 1200, it does that repeatedly.

I’m Trying to Help. Not Enough Information.
I Thought Montero Was A Mercury Model, But I Don’t Find A 2002.
Foreign Cars (Asian, European, Etcetera) Are Not Sold Near Me.
If A Montero Is A Model And It’s A Foreign Make, Please Tell What Make It Is. Thanks.

CSA

It still sounds like a vacuum leak. Take an unlit propane torch & feed propane all around the throttle body & intake manifold. Alternatively just spray around there with anything you have such as carb or throttle body cleaner. If you hit a leak the engine will respond.

I know that you cleaned the IAC, but you might also wonder about how well it is functioning.

It is a Mitsubishi Montero Sport 2002. The engine is 3.5 V6. Really goofy layout with the inlet manifold sitting on top of the spark plugs and all that.

As expected I got a P0507 now. And highly increased gas consumption. I am going to try with the Carb cleaner.
Also the vacuum hoses that are sold in Advance auto look quite cheaply made. Is it advisable to use Silicon Vacuum hoses.

Vacuum hoses, and vacuum switch etc check good. I sprayed carb cleaner and checked for engine to respond.
I found that there is a screw for idle adjustment that my lovely mechanic had pulled out almost all the way when the issue with low idle surfaced. (by the way he did not bother to clean the throttle body or the IAC motor housing)
I warmed up the engine, and then adjusted the screw to get an idle around 800.
Removed/reconnected the battery to get the ECM to retrim the idle, and now it is idling at around 800, the rpm climbs up and then settles down again when you turn on the AC or engage gear.
I am enclosing pictures of this blasted screw. Also note the gasket material sticking out near the throttle body. There is no leak there but it looks like a handy work of some similarly talented repair person.
Thanks for all the help, hopefully this issue is resolved. On this vehicle I am now going to replace the PCV valve every year. I did not know that it can foul up the whole air inlet system.