Hello
My 00 Acura RL starts and runs at a normal rpm but when it is cold outside and the car gets to operating temperature if you put the car in neutral or Park the rpms will jump up to 2000 rpms and if you tap the accelerator will go from 1000-1500 rpm. When it is hot outside it does not fluctuate at all, all summer it idled normal both at start up and at operating temp. At about 50F outside it starts to show these symptoms but sometimes the idle smoothes out after 2 minutes. It seems the colder it gets (now 5F) the higher the rpms will go and I haven't noticed it stopping yet but I will check. At current temps the idle goes from 2200 rpms to fluctuating without me touching the gas pedal. When I first had it checked at a shop it had IAC codes (will have to check) and both IAC valves have been replaced with OEM new. Coolant flushed and new radiator cap. What else can it be?

 

I cant find the link here at work because YouTube is blocked, but if you google ericthecarguy he shows you what to check and if there isnt air there is a valve on the TB that sometimes works its way loose that will cause a surging idle when the car is cold. Hope that helps at least to get you started.

 

Ok thanks I will do that.

 

From what I found (he didn't have a video specifically for RL) there are 3 main causes: air pockets in coolant, vacuum leaks, or dirty or faulty sensors (IAC, coolant temp sensor)

 

I'm having this problem right now. It will go up and down in D at stop light. I need to clean out the throttle body tomorrow and see if it helps or not.

 

How long have it been doing that? Have you added/flushed coolant recently?

 

Like the past week. My bro borrowed the car and now since I got it back it had P0174 which bank 2 is too lean. Don't know what kind of gas he put in but I have like half a tank of unknown gas. I'll run till it empty and fill with good gas and try to find any vaccum leak. Btw, I only add water to the coolant resivior.

 

First make sure coolant is bled and is topped up. If that doesn't help in a day or so you can try cleaning out your idle air control valve on the throttle body.


You can recognize it by the 2 coolant lines going into it. A little bit of throttle body spray and some drops on the concrete should brek it looses if its sticking. If that doesn't work you might need a new one or possibly a different air leak or component.


From my experiences with Hondas over the years its usually the 2 options I stated. Sticky tstat could do it as well but it less likely.

 

Ok, I removed the intake and clean the throttle with cleaner and the code came back in two days. So that is not the problem and i'm not sure where is the IAC is. Anyway, does anyone where is the bank # 2 on the engine, driver or passenger side? Is the red circle is the IAC? How do I remove it and do I need to bleed the coolant system after? Thanks.
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The idle air control valve is the big piece on the top of the throttle body with 2 10mm screws facing the front side. Its just to the left of your circle

 

Is it this one, the one circle in orange? thanks
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Yes that's the one

 

So I just remove it, clean with carb cleaner and maybe a good tab to it then hopefully it will solve the problem. Thanks.

 

Ok, I just check on ebay and the one I circled in orange is called Fast idle control not idle air control vavle. I'm kind of confuse.

 

Yes its the fast idle valve. when the car is cold it speeds up the idle until warm then it drops the idle down to normal.


When you have abnormal idles that seem temperature related or you have a looping idle this is almost always the cause.


Sometimes even cleaning it out and banging it a couple of times to break it looses doesn't help and you need to purchase another one.


You did double check and loosen the coolant bleed screw until coolant came out correct?

 

OMG, I'm keeping get the code P0174, bank #2 is too lean. Even after I changed out the intake, cleaned the throttle body and checked for loose vacuum holes. When I start the car, it idling normal first from 1500 then when it warm up drop to 500~600 rpm range. Now when I'm in D gear and stop at the red light the idle fluctuates up/down from 500~700 rpm range. Sometime it wants to stall but it doesn't and I can fell the engine is shaking. I'm planning to clean out the fast idle then drive it and wait to see if the code will come back on. Second i will clean the idle air control then bleed the cooling system. I will check for vacuum leak last.