Rpm drop when stopping.

[Hodgeee]

Thanks for the tip.

 

[Hodgeee]

Canceled throttlebody order. This morning a friend of mine let me put his 2008 Avalanch tb on. Relearned it, went and drove, does the same thing. Put mune back on, relearned and same thing. I do notice that the idle thing starts when its 100 degrees or higher. Being annoyed, took it to a second dealership, explained it, and they tested it, said they have no idea, and they said they have a handfull of customers Tahoes with the same braking problem. They said mine was the worst yet, same problems, no idea. They did also state a lot of customers have come in and suffer from vapor lock.

At least they didnt charge me the $189 diagnostic fee that the other Chevy dealership did.

So back to square one, i guess ill just live with it.

 

[Dustin Jackson]

Sometimes you just gotta pick your battles for your own sanity

 

[Foggy]

When the ambient temps are up - 100* like you mentioned, the intake air
temps will be 10-20* higher..
At those temps the timing tables pull quite a bit of timing advance out to
protect the engine. I would put money on it that is the issue. When you pull out
timing advance at idle type rpms, the engine runs ****** and can even stall a bit.
If you don't experience this at lower temps, then this is the issue and there's nothing
that can be done ... The only cure would be to set the idle up about 50-100 rpm which
is what I've done anyway as these things idle a little too low in gear

 

[Doubeleive]

maybe find a local tuner and have them look at it and try bumping the idle up 100rpm, some people do that to smooth out the idle

 

[Marky Dissod]

You could, not sure it'll address this symptom specifically, but can't possibly hurt.
I'm wondering if your alternator is just beginning to show the very first signs of aging past its prime?

Tested, seems fine, charges at 14.4volts, plus new battery.

When you tested it, was everything else in the car already ON? That's a bit more of a test, especially at the low-as-possible OE idle.
Which brings me to ...

find a local tuner and have them look at it and try bumping the idle up 100RpM, some people do that to smooth out the idle

Most ten-year-old vehicles appreciate an ever-so-slightly raised idle; among the MANY benefits of getting tuned.

 

[swathdiver]

This is almost always a throttle body issue. What is the percent at idle? Even after cleaning and old worn out throttle body can still do this.

Anyway, if you don't want a new throttle body, have a tuner raise the idle 50 rpms.

It is SOP for @BlackBearPerf to raise the idle speed 50 rpms to eliminate this condition before it even starts as the cars age.

On another note, are any of your engine vent or PCV hoses damaged or kinked? Any issues with the exhaust system? Any engine driven accessories causing a high load? What's the load % or Torque on the engine at idle?

 

[Hodgeee]

I have a tuner that i can look at load, thought about that but never tested it, will check it out tomorrow. They said too late to cancel throttle body, but i can return it once i get it. Might just keep it, especially i trust an AcDelco unit better than the Doorman. Had issues in the past with Doorman items.

Thanks for all the great input! And yes, checked for any kind of vacuum leaks, and replaced the vacuum lines, checked the intake gaskets also.

 

[SNES Avalanche]

Uneven Idle is getting progressively worse but cannot find the cause (Fuel Pump / Injectors?)

Hey all, I drive a 2008 Chevrolet Avalanche (Body has 150k Miles Engine has 40k Miles...AFM sure is great) 6.0 L L76 V8 (gasoline) with a GM 4L70 transmission. I have an issue where the truck's idle has been getting progressively worse over the last few months. Issue: When at a stop the idle...

www.tahoeyukonforum.com

For whatever reason some of us are unlucky and our trucks just don't enjoy idling. I tried almost everything you can think of and to this day I still get the shakes at stoplights.

Tuning my idle RPM helped as it no longer bogs down but at idle the truck vibrates.

 

[Hodgeee]

Ok, bumped the idle from the factory 550 in gear, and 500 in park or nuetral up 50rpms on both. So rpms are still dropping down to 350 when braking, and now its starting to do it even at low speeds, but i think its the temperatures causing it. When it was cooler out it only did it on medium to hard braking. It did make it a little peppier off the line, so will keep the new settings, or do you guys recommend setting it to 650, which seems alot.