Offroad Trailblazers and Envoys

Rough idle after disconnecting battery

Something not working right?

by bhoglan » Tue May 24, 2016 9:44 pm

Hi Folks, it's me again.

So, this weekend I replaced my driver's side CV Axle as well as my Thermostat. Aside from learning that GM's alternator placement engineer is a sadist, I ran into some strange behavior when we were done.

The battery was disconnected so I didn't kill myself on the alternator. When I reattached the battery and started the truck, it had a rough/unstable idle that would dip down to almost dying and then jump back up. This happened both times (I had to rip it all apart again and replace the O-ring because the thermostat ate the first one when I torqued it down). The second time the truck actually died a few times. Both times it seemed to correct itself once the engine was well up to temperature.

Now, I assume that when the ECU loses power, it'll have to relearn certain values from the engine as it heats up. I'm not terribly familiar with ECU designs but I figured that a lot of the engine management values would be on non-volatile storage so they don't disappear when power is pulled. The alternative, I guess, would be for the ECU to have a battery inside it to keep the values when main power is pulled.

So, my question: Is it normal for a TB to act like a jerk after the battery has been pulled. If not, does the ECU have its own battery that I need to check? If not, what are your guesses?


Thanks!
Brian
bhoglan
Cruiser
 
Posts: 13
Joined: Sat Jan 09, 2016 1:45 am
Name: Brian
Vehicle Year: 2003
Vehicle: Chevrolet TrailBlazer
DriveTrain: 4WD w/ G80

by bartonmd » Tue May 24, 2016 10:02 pm

Idle relearn. Normal.
bartonmd
Contributing Author & Off-Road Vendor
 
Posts: 4460
Joined: Wed Sep 09, 2009 9:35 am
Location: IN, Indianapolis
Name: Mike
Vehicle Year: 2007
Vehicle: Chevrolet TrailBlazer
DriveTrain: 4WD w/ G80
Rank: Offroad Rated

by v7guy » Wed May 25, 2016 2:06 am

Yup, normal
build thread

All things in moderation, including moderation.
Some people never go crazy... what truly horrible lives they must lead
User avatar
v7guy
Moderator
 
Posts: 3709
Joined: Wed Mar 09, 2011 10:17 pm
Location: NY, long island
Name: Jason
Vehicle Year: 2004
Vehicle: Chevrolet TrailBlazer
DriveTrain: 4WD
Rank: Offroad Rated

by PROSPHOTO » Wed May 25, 2016 2:25 am

I would speculate that the idle relearn is more noticeable the dirtier the throttle body and IAC motor are... Something that needs to be cleaned routinely on these vehicles.
-Mike
PROSPHOTO
Cruiser
 
Posts: 39
Joined: Wed Apr 13, 2016 9:12 am
Location: Long Island, NY
Name: Michael
Vehicle Year: 2006
Vehicle: Chevrolet TrailBlazer
DriveTrain: 4WD w/ G80

by v7guy » Wed May 25, 2016 3:53 am

There is no idle air control motor on the I6, fortunately cleaning those things are behind us!
build thread

All things in moderation, including moderation.
Some people never go crazy... what truly horrible lives they must lead
User avatar
v7guy
Moderator
 
Posts: 3709
Joined: Wed Mar 09, 2011 10:17 pm
Location: NY, long island
Name: Jason
Vehicle Year: 2004
Vehicle: Chevrolet TrailBlazer
DriveTrain: 4WD
Rank: Offroad Rated

by PROSPHOTO » Wed May 25, 2016 4:01 am

My bad, the butterfly itself acts as the IAC, carbon build up around the edges where they contact the inside of the TB would yield the same symptom
-Mike
PROSPHOTO
Cruiser
 
Posts: 39
Joined: Wed Apr 13, 2016 9:12 am
Location: Long Island, NY
Name: Michael
Vehicle Year: 2006
Vehicle: Chevrolet TrailBlazer
DriveTrain: 4WD w/ G80

by bhoglan » Wed May 25, 2016 4:52 pm

Ok thanks for the advice. How do you folks clean your TB's? Are we talking a seafoam kind of thing?
bhoglan
Cruiser
 
Posts: 13
Joined: Sat Jan 09, 2016 1:45 am
Name: Brian
Vehicle Year: 2003
Vehicle: Chevrolet TrailBlazer
DriveTrain: 4WD w/ G80

by Rickalicka18 » Wed May 25, 2016 6:22 pm

Its been done before. Check youtube for it. I believe some guy did a tutorial on it using his trailblazer.

As for other ways to clean, that's all I have heard of for cleaning carbon build up
Rickalicka18
Addict
 
Posts: 502
Joined: Fri Sep 18, 2015 6:36 pm
Location: Sabattus, Maine
Name: Ricky lacombe
Vehicle Year: 2006
Vehicle: Chevrolet TrailBlazer
DriveTrain: 4WD w/ Limited Slip

by TBYODA » Wed May 25, 2016 10:27 pm

2008 TB Radflo coil overs, Z71 rear springs, 2" spacer, skyjacker N8030 shocks, LT285/75R16E Goodyear MTR

My Build ----- MY Youtube Channel
User avatar
TBYODA
Moderator
 
Posts: 1733
Joined: Mon Apr 01, 2013 9:07 pm
Location: NY, Rochester
Name: Robert Sengillo
Vehicle Year: 2008
Vehicle: Chevrolet TrailBlazer
DriveTrain: 4WD w/ Limited Slip
Rank: Offroad Rated


Return to Troubleshooting