Problem after cleaning throttle body. - Chevy TrailBlazer, TrailBlazer SS and GMC Envoy Forum



Welcome Enthusiast! If you already own a Chevy TrailBlazer or GMC Envoy or perhaps thinking of purchasing such a vehicle, then you have come to the best TrailBlazer and Envoy site on the net! Rainier, Bravada, Ascender, and 9-7x owners welcome too!

You are currently viewing our site as a guest which gives you limited access to view most discussions and access our other features. By joining our free community you will have access to search and post topics, communicate privately with other members, respond to polls, upload content, and access many other special features. Registration is fast, simple and absolutely free so please, join our community today!

If you have any problems with the registration process or your account login, please contact contact us.
Join Today!
Go Back   Chevy TrailBlazer, TrailBlazer SS and GMC Envoy Forum > 2002 - 2009 TrailBlazer/Envoy Tech > 02-09 Vortec 4.2L I-6 Engine and Drivetrain

02-09 Vortec 4.2L I-6 Engine and Drivetrain Q&A forum for engine and drivetrain repairs/modifications/tuning.

TrailVoy.com is the premier GMC Envoy Forum on the internet. Registered Users do not see the above ads.
 
 
Thread Tools
  #1  
Old 02-21-2009, 05:43 PM
Gerbi Gerbi is offline
Junior Member
 
2002 Chevy TrailBlazer LT EXT
Black 4.2L I6 4X4
Join Date: Feb 2009
Location: Somewhere Out There
Posts: 21
Unhappy Problem after cleaning throttle body.

Hi all, new here. Found this place when looking to change the fuel filter.

Anyway, my mom said her 2002 TrailBlazer isn't running "the same" as it used to. I never drive it myself so I really didn't see much problem with it. But she insists it is more sluggish than usual.

So I planned to change the air filter, plugs and fuel filter. While searching for this I found many treads that people all had good luck simply cleaning the throttle body out. It has 101K on it at the moment and as far I I know the air filter was changed maybe 1 or 2 times, fuel filter and plugs were never changed.

Here is the article I used:
http://forums.trailvoy.com/articles....ticle&artid=91

Anyway, first I change the air filter to a K&N filter and at the same time I follow the instructions to clean the throttle body. It wasn't nearly as dirty as the one in the picture but I cleaned it and everything seemed to go as the instructions said it would.

So i put it all back together, triple check connections, and start it up. During the first 5 minutes all seemed OK. Was idling around 1100 RPM and throttle response (while in park) seemed instant. Well the problem is the longer I let the truck idle the RPM gradually kept getting lower and lower at idle. Eventually it seemed to settle at 600 RPM. I have no idea if that it good or not, but the problem is if I let it sit for about 30 seconds, apply throttle it seems to bog\hesitate then jump to 1200-1500 rpm, then I let of the throttle it drops to 700 RPM, then back to 800-900, then back down to 600. So letting off the throttle it jumps around a bit before settling back at 600 rpm. (Now if i rev it to 1500, then let it settle to 600 , then immediately rev again I hardly see the bog at all, but let it sit 30 seconds to a minute at it bogs on initial acceleration.)

I have not taken it for a drive in fear that something is wrong, so all this was done while in park and revving the engine to 1500 slowly.

I had driven the truck not too long ago and I am almost positive it idles around 1k and I don't remember this hesitation I am experiencing that is very obvious right now, almost as if it wants to stall, but the engine doesn't get to the point where it shakes or sputters.

Any advice? Or need more information?

Thanks
Quick reply to this message
Sponsored Links
Advertisement
 
  #2  
Old 02-21-2009, 05:51 PM
sonomacrewcab's Avatar
sonomacrewcab sonomacrewcab is offline
Member
 
2002 Chevy TrailBlazer LTZ
Light Pewter Metallic 4.2L I6 4X4
Join Date: Mar 2008
Location: leduc, ab
Posts: 205
are trucks once warmed up, should drop down to 600rpm or a little bit higher for the idle.
Quick reply to this message
  #3  
Old 02-21-2009, 05:54 PM
freakimp77's Avatar
freakimp77 freakimp77 is offline
Member
 
2002 GMC Envoy SLT
Midnight Blue Metallic 4.2L I6 AWD
Join Date: May 2007
Location: Jupiter, Florida
Posts: 259
I had that happen when I put my new system in and cleaned my engine a bit. I don't know what it is, but driving, it's fine for me. Take it for a test drive up and down the street and see what you think.

For me, it settles out as soon as it's put in drive, but even now, after a few months, it still does it SLIGHTLY when I rev in park.

but anyway, take it for a test drive and see what you think
__________________
I bleed garnet and gold!
Quick reply to this message
  #4  
Old 02-21-2009, 05:56 PM
the roadie's Avatar
the roadie the roadie is offline
No longer with us
 
2004 GMC Envoy SLT "Roadiemobile"
Extreme Offroad Pewter 4.2L I6 4X4
Join Date: Apr 2005
Posts: 26,181
Yes. 600 RPM is the target idle speed. A bit higher when cold. But since you disconnected the battery to clean the TB, you have to drive it for a while (30-60 minutes?) to get the PCM to relearn the adaptive tables it needs to predict where to put the throttle for various RPMs. You're teaching a baby to walk, and pulling the battery just erased all the lessons it's spent years learning.

If you don't have the Service Engine Soon light on, then there's nothing so horribly wrong that you can't take it for a drive.
Quick reply to this message
  #5  
Old 02-21-2009, 05:58 PM
Gerbi Gerbi is offline
Junior Member
 
2002 Chevy TrailBlazer LT EXT
Black 4.2L I6 4X4
Join Date: Feb 2009
Location: Somewhere Out There
Posts: 21
Thanks for the reply, if that is the case then the RPM seem fine and I can assume the plugs or fuel filter are to blame. maybe the clean throttle body made the bog more obvious? I would believe that, but the fluctuating RMP after I lift the throttle is bothering me.

I did pull 1 plug out to inspect it, it seemed OK for 101K. I would have replaced them but AutoZone sold me Bosh plugs because they said AC Delco didn't make them for my truck. I read on here they infact do and the Bosh plugs suck. So I have to find a place that has AC Delcos.

I can take a picture of the plug if you think it will help. Just trying to figure out what I am chasing here.

BTW, nice site, wish there was one like this for pontiac.

Thanks
Quick reply to this message
  #6  
Old 02-21-2009, 06:02 PM
Gerbi Gerbi is offline
Junior Member
 
2002 Chevy TrailBlazer LT EXT
Black 4.2L I6 4X4
Join Date: Feb 2009
Location: Somewhere Out There
Posts: 21
LOL, wow, this forum really moves! My last reply was after the first guy responded, then I see 2 more once I hit post!

OK, now I feel better about taking it for a test drive. Sounds like my truck is running like it should. I don't see the service engine soon light on so I'll try it out tomorrow (It is already dark for me, so I'd rather do it in the daylight in case I have a problem).

Thanks
Quick reply to this message
  #7  
Old 02-21-2009, 06:19 PM
sctb's Avatar
sctb sctb is offline
Senior Member
 
2005 Chevy TrailBlazer LS
Summit White 4.2L I6 4X4
Join Date: Feb 2008
Location: Clinton SC
Posts: 607
Sounds normal. I Seafoamed mine today before changing the oil. Ran a little less than 1/2 can through the vacuum line and added the rest to the oil. Then I let it idle to clean whatever it would.

600-625 is the correct idle. Usually on starting, mine will go up to about 1100-1200 when cold, then start dropping. There is a lag in revving, primarily due to the drive by wire system. When I rev it, the RPM's go up (1100), down (700-800), up slightly (900 or so), then settles back down (700ish). Once the temp needle starts to move, it is usually on 600 at idle. I don't think you have anything to worry about, but it will drive a little funny while the PCM relearns.

At 101k, you probably should go ahead and do the plugs anyway. Can't hurt.
__________________
Phillip

Eagles may soar, but weasels don't get sucked into jet engines.
Quick reply to this message
  #8  
Old 02-21-2009, 06:29 PM
Gerbi Gerbi is offline
Junior Member
 
2002 Chevy TrailBlazer LT EXT
Black 4.2L I6 4X4
Join Date: Feb 2009
Location: Somewhere Out There
Posts: 21
Thanks sctb, what you just described sounds like what is happening to me. Since it isn't my truck and my 07 GMC Sierra doesn't do it i assumed it was something wrong.

Just to be sure we are on the same page, i found this Youtube video of another member on here, he videos the RPM and also notes the second rev in RPM is not his doing, mine looks the same.

http://www.youtube.com/watch?v=xOVUq4PJmnw

I'll take it for a spin tomorrow and see how it is while in drive. My concern is when at a stop, but I'll report back tomorrow.

Thanks
Quick reply to this message
  #9  
Old 02-21-2009, 07:00 PM
sctb's Avatar
sctb sctb is offline
Senior Member
 
2005 Chevy TrailBlazer LS
Summit White 4.2L I6 4X4
Join Date: Feb 2008
Location: Clinton SC
Posts: 607
Quote:
Originally Posted by Gerbi View Post
Thanks sctb, what you just described sounds like what is happening to me. Since it isn't my truck and my 07 GMC Sierra doesn't do it i assumed it was something wrong.

Just to be sure we are on the same page, i found this Youtube video of another member on here, he videos the RPM and also notes the second rev in RPM is not his doing, mine looks the same.

http://www.youtube.com/watch?v=xOVUq4PJmnw

I'll take it for a spin tomorrow and see how it is while in drive. My concern is when at a stop, but I'll report back tomorrow.

Thanks
That's it. Mine does same as the video. I'm pretty sure it has to do with the drive by wire. Even Seafoaming, which promises less hesitation, won't totally fix it...there will always be a slight lag when you press the throttle and when the engine responds. Then it bumps the RPM when it settles out. Why? Who knows except GM and the software. Possible, I guess that the butterfly in the throttle body is resetting itself?? Or some other slight adjustment the PCM is making??
__________________
Phillip

Eagles may soar, but weasels don't get sucked into jet engines.
Quick reply to this message
  #10  
Old 02-23-2009, 01:22 AM
Gerbi Gerbi is offline
Junior Member
 
2002 Chevy TrailBlazer LT EXT
Black 4.2L I6 4X4
Join Date: Feb 2009
Location: Somewhere Out There
Posts: 21
I took the truck for a trip today, about 90 miles round trip, about 75% highway. So far everything seems fine, runs at 2100 rpm at 70 mph. I never experienced any bogging or hesitation through the entire trip. It does still do the weird throttle jump when in park just like that video, but everything else seems fine.
Quick reply to this message
Sponsored Links
Advertisement
 
 

Quick Reply
Message:
Options

Register Now

In order to be able to post messages on the Chevy TrailBlazer, TrailBlazer SS and GMC Envoy Forum forums, you must first register.

Please enter your desired user name, your email address and other required details in the form below.
(Only letters, numbers, dashes and underscores are permitted for user names)
The user name that you choose is permanent and can never be changed.
User Name:
If you do not want to register, fill this field only and the name will be used as user name for your post.
Password
Please enter a password for your user account. Note that passwords are case-sensitive.
Password:
Confirm Password:
Email Address
Please enter a valid email address for yourself.
Email Address:

Log-in

Human Verification

In order to verify that you are a human and not a spam bot, please enter the answer into the following box below based on the instructions contained in the graphic.




Currently Active Users Viewing This Thread: 1 (0 members and 1 guests)
 
Thread Tools

Posting Rules
You may not post new threads
You may not post replies
You may not post attachments
You may not edit your posts

BB code is On
Smilies are On
[IMG] code is On
HTML code is Off

Forum Jump


» Sponsors

Advertising Info

All times are GMT -4. The time now is 04:46 AM.


Chevy TrailBlazer and GMC Envoy Enthusiasts - Copyright 2004 - 2009 All Rights Reserved.
All trademarks referenced herein are property of their respective owners.
RSS Feed