Cold Start - Fast Idle

Just purchased a 2.7L and noticed that when cold (even in the summer at 70 degrees) it idles at 2K to 2200 upon start up.

Then after a few minutes I hear some type of click and the idle slows way down to almost normal hot idle speed. The click almost sounds like the a/c compresssor is being turned off when the idle slows down.

Is this normal for this engine?

 

mine idles high on cold start up, around 1000-1100, i think, but nothing like urs!

 

There are times when mine will fast idle from a dead cold start at 2000 RPM, but it backs down to 1500 or so in a few seconds. The other day on a very hot day that the truck sat out in the direct sun for 8 hours, when I started it, the cold start cycle didn't even happen and it idled at 700 RPM . If yours is idle is that high for two minutes something is wrong with the cold start cycle of the ECU.

 

been idling at less than 1500 but above 700 all day any weather, 2000 seems high IMO

 

one thing you can do to lower your idel if it bothers you is to buy a Pro dry S filter and remove the secondary charcoal filter. it will lower your idel rpms to about 1000 or even less

 

mine def. goes up tp abput 2k at cold startup i usually put it in gear b4 if goes down, but putting it in gear drops it

 

that is exactly what I've been doing also..

 

Sounds normal to me. 2000 may be higher than most people see but its not abnormally high. I'd say you are alright.

 

Mine does the same thing... always comes down in less than a minute (but I haven't had it in the winter yet)

 

can you explain to me in techinical terms why a dirty MAF would cause a fast idle only during the first 60 seconds of cold start up?

 

and why would this only impact the engine idle when its cold and not hot?

 

In winter under about 30 degrees it may go even higher. I've seen 2500 for a few seconds when it sits out in really cold weather.

 

I wouldn't worry about it. I have the same engine and it tends to idle a bit high for probably 30 seconds or so. The engine does this to warm up quicker.

 

Two reasons why, one is emissions. The faster it warms the less it pollutes. The main reason is poor running concerns. In a cold engine the fuel does not mix well with the air. It will actually pool up rather than turn to vapor. Only the vapor burns, the liquid fuel does not. The faster and engine runs the quicker it warms up.

 

It wouldn't. The engine runs in closed loop mode when its warming up and doesn't use the signal from the MAF.