rpm/voltmeter problem

mrm143

Original poster
Member
Feb 29, 2012
42
Hello everyone
New owner of an 05 envoy SLT
Saw the forum, and looks to be a wealth of knowledge, and I am glad to be a part of it

So....
My question

If your in the truck at a stoplight, every once and a while the RPM's will drop and go back up, almost like something put a heavy load on the battery.
It is almost like turning on the AC when the compressor kicks on, but I have tried with the AC on and off, and it still does it...

If I turn the ac on, it does kick down, but not quite as much as the problem I am having.

Any advice?:smile:
 

Black_tb

Member
Dec 6, 2011
817
maybe cleaning the throttle body
 

HARDTRAILZ

Moderator
Nov 18, 2011
49,665
Try cleaning the throttle body. These trucks actuallly really need it done regularly.
 

mrm143

Original poster
Member
Feb 29, 2012
42
HARDTRAILZ said:
Try cleaning the throttle body. These trucks actuallly really need it done regularly.

Sounds like a plan, and not to bad to do it, BUT, does that sound like a symptom of the TB as it feels to me like something putting some kind of strain on the engine, like turning all the lights on at once if you know what i mean

HARDTRAILZ said:
Try cleaning the throttle body. These trucks actuallly really need it done regularly.

Sounds EXACTLY like this, MINUS the codes

http://gmtnation.com/f24/advise-please-idle-issue-code-p0502-1649/
 

HARDTRAILZ

Moderator
Nov 18, 2011
49,665
Yes. Weird idle is often solved by the cleaning. Depending on your mileage, plugs might be a good idea as well. Only use the Delco Iradium ones.
 

mrm143

Original poster
Member
Feb 29, 2012
42
mrm143 said:
Sounds like a plan, and not to bad to do it, BUT, does that sound like a symptom of the TB as it feels to me like something putting some kind of strain on the engine, like turning all the lights on at once if you know what i mean




Looked at other threads, and all the same symptoms, I have 142k on engine, and bet its dirty as all hell... Just was confused as at first glance it seemed more electrical than enything... I will clean it and let you know... Thanks again for the help

HARDTRAILZ said:
Yes. Weird idle is often solved by the cleaning. Depending on your mileage, plugs might be a good idea as well. Only use the Delco Iradium ones.

43-101 right?
 

Mark20

Member
Dec 6, 2011
1,630
I was having the same problem at 65k or so and its fine after cleaning it. The edges of the butterfly valve are sharp so watch your fingers.
 

mrm143

Original poster
Member
Feb 29, 2012
42
Mark20 said:
I was having the same problem at 65k or so and its fine after cleaning it. The edges of the butterfly valve are sharp so watch your fingers.

I read the how to but can I move the butterfly without damaging anything and I heard a toothbrush is the scrubber of choice?

Do I spray anything into the open intake as well since its off
 

MAY03LT

Member
Nov 18, 2011
3,412
Delmarva
mrm143 said:
I read the how to but can I move the butterfly without damaging anything and I heard a toothbrush is the scrubber of choice?
You can move it manually, it will be fine. And yeah, the toothbrush works great.

mrm143 said:
Do I spray anything into the open intake as well since its off

I never have.
 

mrm143

Original poster
Member
Feb 29, 2012
42
MAY03LT said:
You can move it manually, it will be fine. And yeah, the toothbrush works great.



I never have.

Thanks... ill freak my wife out with the learning procedure afterwards lol....
 

Voymom

Member
Feb 3, 2012
2,523
Depending on how dirty your Throttle body is you are going to want a cleaner. I used just some red can that said throttle body cleaner spray lol it was cheap so I bough it. My truck has 114k never had the throttle body cleaned and it was NASTY, took me a little over 45 minutes total to clean and that was with a tooth brush as well.

I also have the same idle issues...or I did anyways. I cleaned my throttle body and most of my low power and throttle response issues went away. I do however need to make sure my cat converter is not clogged and i'm replacing my sparkies this weekend. How does your thermostat look? I had a dying t-stat and when I replaced it a lot of my issues were solved, but definitely clean that throttle body and make sure you do it as regular maintenance every 30k miles or so. I will never allow mine to be as bad as it was...Oh and make sure you have plenty of towels lol

Throttle body before

IMG_20120226_181729.jpg


And after

IMG_20120226_184817.jpg


I have an 03 Envoy SLT
 

mrm143

Original poster
Member
Feb 29, 2012
42
Nasty lol
Tstat is fine right in the middle

Only other thing I get is the little bump when you come to a stop which I read up on and the driveshaft splines need.to be greased I believe... looking for a writeup for that one now:thumbsup:

Ps.... is their any gasket in their when I put it back on?
 

HARDTRAILZ

Moderator
Nov 18, 2011
49,665
mrm143 said:
Nasty lol
Only other thing I get is the little bump when you come to a stop which I read up on and the driveshaft splines need.to be greased I believe... looking for a writeup for that one now:thumbsup:
There is not much to write-up. Take the 4 bolts out that hold the rear u-joint in place. Take the u joint loose from the pinion, lower it and slide the whole shaft to the rear and the splines will slipe out. Grease the splines and slide back in. Reattach the ujoint and good to go.


mrm143 said:
Im assuming better gas mileage too?

Better MPG from what? The throttle body and plugs may help some as any maintenence will, but not enough to be very noticable.
 

The_Roadie

Lifetime VIP Donor
Member
Nov 19, 2011
9,957
Portland, OR
mrm143 said:
...the driveshaft splines need.to be greased I believe... looking for a writeup for that one now
Remove U-joint bolts at the rear end of the driveshaft. Drop driveshaft, slide rearwards out of the transmission or transfer case tailpiece. Grease. Reinstall.

axle112.jpg


DRAT. Scooped by Kyle. Snooze = Lose. hehe
 

HARDTRAILZ

Moderator
Nov 18, 2011
49,665
But you came through with a picture...
 

mrm143

Original poster
Member
Feb 29, 2012
42
Im thinking about going to do it now but its cold and rainy... bit once I have it out the rest I can do indoors
 

Black_tb

Member
Dec 6, 2011
817
also when you clean the throttle body be sure to disconnect the battery for at least thirty minutes so when you connect everything back up the computer can make adjustments
 

Wooluf1952

Member
Nov 20, 2011
2,663
Milwaukee, Wisconsin
Just an FYI,those u-joint bolts are only 15 ft. lbs.
You don't want to crush the bearing caps. :thumbsup:
 

mrm143

Original poster
Member
Feb 29, 2012
42
Cleaned the TB thanks to everyone for the help BUT

The truck doesnt seem to be doing the whole "relearn" thing.. Battery was disconnected for about 45 mins


Does it just not do that sometimes, or is their something I can do to force it...

Also the Avg MPG is now at 0.0 and not moving at all? Maybe it is part of the whole disconnected battery thing
 

mrm143

Original poster
Member
Feb 29, 2012
42
Disregard the mpg thing..

Its running but still doing the rpm thing and a bit more often.... if it needs to learn I want to make it lmao unless it belongs on the short bus it may be a slow learner

Im actually sitting here now.in front of my house and its really dipping now.... could it still be learning been driving for almost 40 mins....
 

MAY03LT

Member
Nov 18, 2011
3,412
Delmarva
mrm143 said:
could it still be learning been driving for almost 40 mins....

After I do the cleaning/resetting, I drive an 8 mile loop to do the relearn and make sure everythings cool. By then, it is.

Usually the throttle body cleaning/pcm reset is the fix when the rpm or stalling issues come up after the battery is disconnected. It didn't say if this was the case in your first post.
 

mrm143

Original poster
Member
Feb 29, 2012
42
MAY03LT said:
After I do the cleaning/resetting, I drive an 8 mile loop to do the relearn and make sure everythings cool. By then, it is.

Usually the throttle body cleaning/pcm reset is the fix when the rpm or stalling issues come up after the battery is disconnected. It didn't say if this was the case in your first post.


Throttle body cleaned and is spotless but no change a little peppier acceleration..
How can I reset the pcm manually as the battery disconnect for 45 mins didn't seem to do anything I was expecting the truck to run like crap for at least 20 mins which it didnt
 

MAY03LT

Member
Nov 18, 2011
3,412
Delmarva
mrm143 said:
How can I reset the pcm manually

Remove power from the pcm for 30 minutes, whether by disconnecting the battery, or removing fuses 10 and 28 in the front fuse block.

mrm143 said:
the battery disconnect for 45 mins didn't seem to do anything I was expecting the truck to run like crap for at least 20 mins which it didnt

It won't. I usually see subtle idle changes during the first few minutes but not what you're experiencing. That's why I wondered what started the rpm change in the first place.
 

mrm143

Original poster
Member
Feb 29, 2012
42
Im still under the 30 day warranty so off to the dealer tomorrow its some kind of missfire and it got worse
 

mrm143

Original poster
Member
Feb 29, 2012
42
Changed Serpentine belt (5 mins very easy) and it's A LITTLE better, dealer told me to change belt and plugs and then to call back.....
 

mrm143

Original poster
Member
Feb 29, 2012
42
So in my previous thread I am having the rpm dip issue
cleaned tb and changed serpentine belt as it was cracking
Still having rpm issue was going to do plugs today but then watch this video from a cold start this morning
Watch the rpm and voltmeter as well as the info center flickering[video=youtube;dZVZC0-g-V4]http://www.youtube.com/watch?v=dZVZC0-g-V4[/video]
 

TexazReece

Member
Dec 4, 2011
1,341
I did see them move a bit go ahead and change the plugs out.............Damn you get 7.8mpg????
 

mrm143

Original poster
Member
Feb 29, 2012
42
I was waiting for the mpg comment I had just reset it lol
Plugs going in today im going to have alt and batt checked at azone too
 

STLtrailbSS

Member
Dec 4, 2011
1,617
Did you unhook your battery after cleaning the TB to reset the pcm values for the dirty TB. May want to check your grounds also, that's my 2 cents for your Voltage issue had the same issue with volts bouncing because of a loose ground terminal.
 

mrm143

Original poster
Member
Feb 29, 2012
42
STLtrailbSS said:
Did you unhook your battery after cleaning the TB to reset the pcm values for the dirty TB. May want to check your grounds also, that's my 2 cents for your Voltage issue had the same issue with volts bouncing because of a loose ground terminal.

Point me in the direction of which ground to check assuming more than just battery terminals
 

Mark20

Member
Dec 6, 2011
1,630
How old is the battery? Had my voltmeter going crazy like yours and it was the battery retiring. I don't remember the engine RPM changing that much though.
 

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