98 k2500 starting issues?

[stelmadl]

i have a 1998 gmc, k2500, 454. when i start my truck, the engine revs to 1900 rpms! is this normal? i hate hearing this thing rev so high in the morning when it's been sitting all night. i use synthetic which probably helps. i have 99,000 miles on her and she only uses 1/2 quart per oil changes (5000mi). any one else have this? i probably wouldn't notice this, but my borla exhaust just makes it stand out because it's loud!

[Truck_Man]

This sounds normal considering the fact that it's doing it when it's cold, It will idle fast when it's cold and as it warms up you will see the idle come back down to normal, you will probably notice it more in cold weather than warmer weather.

[chevyguy]

1900 seems too high. Check for codes even if you havent gotten a check engine light. Sounds like a Idle air control or TPS issue. My 97 never idled over 1100 on start up.

[Truck_Man]

It might be a tad high, chevyguy would know more than me. see what the sevice manual says. I might be thinking of the older carburated vehicles. I remember my grandmothers car would fast idle so fast and it would be loud, Sounded like it was going to take off to the moon. Then again these are totally different vehicles and that can make for quite a variation as every make and vehicle is different.

It will deffinately idle faster when it's cold though.

[chevyguy]

The older vehicle had a fast idle cam on the passenger side of the carbeurator that caused higher idle until heat acted against the preset spring tension. newer fuel injected vehicle have a momentary squirt of fuel to start them and monitor its output thru the exhaust and richen it up or lean it out. Shouldnt idle this high. Older cars did idle quite a bit higher than the newer ones do.

[Itstali25]

^ lol your a genious

[chevyguy]

GENIUS.......he he ,I are one

[Itstali25]

..........WOW, i must have been really tired when i typed that........i can't believe I spelled that word wrong.......silly me

[Truck_Man]

Chevyguy is very smart, of course he has had all the training on these vehicles. Im not so much up on the basics of these newer fuel injected models, I know some but only a little, I only know some basics of old school as i call it. lol. I know my 1999 Gmc Idle somewhat faster when I first start it until it warms up and then as it warms up the computer brings the idle back down to normal. It only fast idles slightly for a couple of minutes though and it's not real fast then it will slowly come back down. The computer does the fast idle work on the newer vehicles.

From what I have heard the computers in these newer fuel injected engines have a cold starting and running program and a warm starting and running program. Chevyguy can correct me if im wrong at all, but the way I understand it the cold starting and running part alows for richer mixture and slightly faster idle and maybe a few other adjustments. Warm programing alows for leaner mixture and slower idle, this being controled by a temp sensor and the computer. Chevyguy if im wrong with any of this please correct me. This is just some basics Ive heard from another mechanic.

[stelmadl]

thanks for the replies guys! where can i find these sensors? are they cheap and easy to replace? i don't have a scanner or access to one, but if it's a cheap and easy replacement, i may do this myself.