idle issue with 2001 denali!!

[socal01denali]

with about 52,000 miles ive been experiencing a problem with my idle it usually happens when i first start up the truck before i push the pedal hot or cold and sometimes at a stop light. it doesnt seem to matter if the a/c or headligts are on. the idle will drop and rise from normal idle speed (around 600) or so to around 100...my headlights and a/c if on will dim and come back with every rpm strike and my battery volts guage will steady drop from 14 volts in sequence with the rpms until i gas it or drive off. i recently installed a new 135 amp alternator because my stock 130 amp was only putting out around 4 amps at 2000 rpm.so i thought that was it... the problem happened that same night. i run 91 octane fuel, occasionally use carb/injector cleaner with a fill up ,my battery reads good, my charging system is good and my fuel filter is clear. any ideas you might have would be great thanks in advance

[GMMerlin]

Originally Posted by socal01denali

with about 52,000 miles ive been experiencing a problem with my idle it usually happens when i first start up the truck before i push the pedal hot or cold and sometimes at a stop light. it doesnt seem to matter if the a/c or headligts are on. the idle will drop and rise from normal idle speed (around 600) or so to around 100...my headlights and a/c if on will dim and come back with every rpm strike and my battery volts guage will steady drop from 14 volts in sequence with the rpms until i gas it or drive off. i recently installed a new 135 amp alternator because my stock 130 amp was only putting out around 4 amps at 2000 rpm.so i thought that was it... the problem happened that same night. i run 91 octane fuel, occasionally use carb/injector cleaner with a fill up ,my battery reads good, my charging system is good and my fuel filter is clear. any ideas you might have would be great thanks in advance

First I would clean the throttle body...deposits on the blade and bore will cause low idle concerns.
If it is a cable actuated throttle body, there is a GM technical bulletin to resolve this issue.
Next, only use the octane rating specified by GM for that engine...using a higher octane fuel can cause cold driveability issues and you are just wasting your money on something you dont need.

[GMCTech]

Clean the throttle body bore as GMMerlin said.

Also GM has a few software updates addressing idle surge and fluctuation. I'm not sure if your vehicle has this availalbe to it, but it's worth the check.

Hope this helps.

[socal01denali]

thanks guys...i will start with the throttle body..HEY GMCTech do i have to go into GMC and pay them....i was planning on getting a hypertech programmer soon...do you think it will have any of these updates??

[socal01denali]

my trucks a 2001 so i figured 91 octane would be fine and even provide a little better performance...but ill check the book

[GMCTech]

Most likely the hypertech programming will overwrite anything the dealership does, try that first if that's your plan.

[socal01denali]

hey gmctech i cleaned out the throttle body with some valvoline synthetic cleaner for carb, throttle body and choke...you guys were right it was pretty filthy and i have the rag to prove it...a put in a few good sprays finished installing my new volant intake then drove around...i will have wait and see if the cleaner helped with my idle issue...but about how much should i spay into the body interior?? thanks!! also to any yukon owner out there i definetly recommend the volant cold air for your truck WOW awesome performance, great low end pick up and response, afforadable and kick ass sound!

[socal01denali]

i guess i should have said how much should have i sprayed or were a few healthy sprays sufficient? thanks

[Tony Denali]

you have the drive by wire system. No cable. My Denali did the same thing and just took it to the delear for a software update and it took care of it pronto.

[ranman7]

check out the recall on the 01 yukon for a misrouted positive battery cable which rubs on the steering shaft and causes different elec. problems