08 Tahoe idle surge at low idle. HELP

[Book_em]

I have a 2008 tahoe 2wd PPV with 240k miles. Not always but at least 6 times a day while in gear at a stop light the idle will drop from 600 to 300 and kick right back up to 600 and act like it never happened. Feels like it wants to stall but doesnt. The only thing the dealership can tell me is my fuel trim reads from 23 to 40 percent but cant tell me why. Keep in mind no codes. Since this started to happen about 4 months ago i have installed the following parts all from GM with no avail. Please help.

New throttle body with tps
New alternator
New belts and pulleys
New starter
New maf and map sensors
New ac compressor
New plugs and wires
New up and down 02 sensors both sides
New transmission
New airbox

Any help or ideas would be greatly appreciated

 

[kbuskill]

Does this happen with your A/C on or off or both???

 

[Book_em]

Does this happen with your A/C on or off or both???

It will happen with both.

 

[Kraig]

I’m going to take a stab in the dark and say you should try the Big 3 (or 4) upgrade and see if it helps. If it doesn’t, it was a good idea anyways.

 

[BG1988]

I have a 2008 tahoe 2wd PPV with 240k miles. Not always but at least 6 times a day while in gear at a stop light the idle will drop from 600 to 300 and kick right back up to 600 and act like it never happened. Feels like it wants to stall but doesnt. The only thing the dealership can tell me is my fuel trim reads from 23 to 40 percent but cant tell me why. Keep in mind no codes. Since this started to happen about 4 months ago i have installed the following parts all from GM with no avail. Please help.

New throttle body with tps
New alternator
New belts and pulleys
New starter
New maf and map sensors
New ac compressor
New plugs and wires
New up and down 02 sensors both sides
New transmission
New airbox

Any help or ideas would be greatly appreciated

fixing random parts eh?


more then likely a vacuum issue... check the vacuum hoses
or faulty
IAC valve (idle air control valve)

 

[992dr]

Welcome aboard John

Mine has done this in the past and does it every so often. Can be pretty annoying. No codes here as well.
I have about 220k miles.
In my most recent research and from what I've read in the last, I had read about fuel injectors causing this same issue. Also something about fuel injectors dripping down. I will be replacing mine this summer.

 

[Book_em]

I’m going to take a stab in the dark and say you should try the Big 3 (or 4) upgrade and see if it helps. If it doesn’t, it was a good idea anyways.

I will be doing this in the coming weekend. Thanks for the idea

 

[Book_em]

fixing random parts eh?


more then likely a vacuum issue... check the vacuum hoses
or faulty
IAC valve (idle air control valve)

At least once i fix these parts i know they are new and when replaced. Im really trying to keep this truck long term.
All vacuum hoses have been replaced and as far as i know this truck doesnt have an IAC valve as its part of the throttle position sensor. Which is new also.

 

[Doubeleive]

have you tested the fuel pressure when this is happening?

 

[Book_em]

Welcome aboard John

Mine has done this in the past and does it every so often. Can be pretty annoying. No codes here as well.
I have about 220k miles.
In my most recent research and from what I've read in the last, I had read about fuel injectors causing this same issue. Also something about fuel injectors dripping down. I will be replacing mine this summer.

Thank you.

I will also look into this as a possibility and keep you posted. Thanks again.