Quick q's guys! I noticed that everytime i start my car... the RPMs are at 1200 or soo... is that normal? its 85F outside and the car was parked for 5 hrs... i mean it doesn't stay that hight for long.. but i'd say in about 2 mins, it dropps to normal idle...

is this normal?

 

Normal .........

 

Yep totaly normal

 

if you're really that concerned, clean the throttle body. It'll take maybe an hour, and idle will be lower.

 

i don't think it'll make much of a difference...if any, it will be so marginal that you won't be able to notice it by looking at the tach needle....1200 is about right because the engine is just trying to warm itself up...the operating temp. is higher than outdoor temperatures, so regardless of how hot it is outside, it will idle at ~1200 when started cold, although it does drop quicker when it's hotter outside...

 

Funny because when I clean mine, it actually goes higher at start-up ...

 

thanks guys! i appreciate the help and everything.. i figured it was fine, but i wanted to make sure!

thank you all!

 

how about high idle when shutting down after driving for about an hour? 1200-1500. i get this all the time. normal?????????

 

A higher idle after any cold start (1 hr or whatever) is normal. As the car warms up, you should notice the idle speed dropping, settling somewhere around 600-700 (depending on auto/spd).

 

After warm, my car idles at about 600. the RPMs are higher at cold start-up to get the correct oil pressure. (When the oil is cold the pressure is lower, so the engine compensates by boosting engine speed)

 

Ahhh...sorry to burst your bubble but it's exactly the opposite....cold temps = higher oil pressures.

The reasons Maxes -or any other computer-controlled car idle faster at start-up is to warm up the car faster, specially to 'light off' their catalytic converters faster, not because of oil pressure which comes up no more than two seconds (often much less) after a cold-soak start.

 

You are trying to tell me that higher temperatures are not associated with higher pressures? Where did you go to school? I think their physics program could use some help.

Also, many new cars (including ours) idle at very low speeds. If we idled at 500 RPM when the engine is cold (and pressure is low) there would not be sufficient lubrication. This in addition to warming up the engine more quickly is the reason for the higher RPMs at start up.

 

NewLoveI30:

Your physics program ever hear of viscosity?

 

NewLove, give me that shovel before you get so deep you can't get out

Galo > j00

 

this looks like fun

 

Yes, I am quite aware of what viscosity is.

Still dont see why engine speed and the low viscosity of cold oil can't work together to acheve proper lubrication. But hey, I've been wrong before

 

At cold oil temperatures the engine's oil pump must work harder to provide an equal volume of oil to the lubrication system. Therefore, oil pressure varies inversely with engine oil temperature. Imagine trying to drink water through a straw vs. trying to drink molasses -- you must exert a higher pressure (suction in this case) to move an equal volume of the substance through the straw in a given time frame.

Old (carbureted) cars idled high to warm up the engine because carburetors had no provisions for adjusting the air/fuel mixture to match engine temperatures other than the choke, and the jetting and enrichment circuits were designed for a warm engine.

Newer cars idle fast to warm up the engine to operating temperature, to lubricate the engine more efficiently, to recharge the battery slightly faster after the drain of the starter motor, and to get the precats hot for EPA cold-start emissions testing. Once it warms up and the thermostat opens the computer can switch its mode of operation to provide the optimal AFR. If you install an oil pressure gauge in your car you will notice that on cold start the pressure will jump from 0 to near the end of its range, then slowly come down as the engine warms up until it is running close to the low end of its range at idle with a warmed-up engine.

FYI -- I'm not disputing anything except your claim that oil pressure rises with oil temperature. You are correct that increased RPM at start-up contributes to improved lubrication.