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#4597211 - 12/07/17 02:43 PM '07 Suburban: post-TB clean idle woes
Alex_V Offline

Registered: 04/10/16
Posts: 1067
Loc: Campbellsville, KY
A friend's '07 Suburban (5.3, 184K) threw P0121 yesterday. Another friend who's plenty capable with all things post-2000 Chevy trucks scanned it, cleared the code, and sent him to me to clean the throttle body.

No CEL when I got it, no strange behavior as I pulled it into the shop. Took the throttle body off the intake but left it plugged in (caught the carb. cleaner and goo in a container) thinking that would avoid having to re-learn the throttle body. Upon startup, idle jumps to 1,700 but doesn't immediately come back down, instead staying right there, then slowly climbing up toward 2,500. Plugged in the scanner to watch the data, played with it for a minute, then took it for 6-mile drive. Runs fine, settles down to idle when in gear, and doesn't jump up high when moved from drive or reverse back to park. However, just like clockwork, when I tap the gas pedal in park the idle jumps up again and doesn't come back down until I put it in gear again. Also, startup idle is still just as high. Data shows desired idle @ 650-700 and actual at whatever speed it's revving, most of the time being ~2,400. Just to check it off the list I pulled the connectors on the TB and gas pedal sensor, inspected and applied dielectric grease - no change. Still no CEL, either.

Any wisdom?
I like Chevy and Valvoline.

'13 Cruze, 1.4T, 110K
'85 GMC C3500, 454, 130K
'82 Mercedes 300CD, OM617 turbo, 165K
'67 Suburban, 350, 331K

#4597230 - 12/07/17 03:00 PM Re: '07 Suburban: post-TB clean idle woes [Re: Alex_V]
mclasser Offline

Registered: 04/13/13
Posts: 2126
Loc: The Northeast
Does the service manual specify an idle relearn procedure?
2018 Hyundai Elantra VE -- 1K
2013 Honda Pilot EX-L 4WD -- 50K
2002 Honda Accord EX-L -- 210K
2002 Infiniti I35 -- 130K

#4597231 - 12/07/17 03:00 PM Re: '07 Suburban: post-TB clean idle woes [Re: Alex_V]
Ethan1 Offline

Registered: 12/29/14
Posts: 1620
Loc: 'murica
Sounds like you need to relearn the idle with a bidirectional scantool. shrug

#4597232 - 12/07/17 03:01 PM Re: '07 Suburban: post-TB clean idle woes [Re: Alex_V]
WobblyElvis Offline

Registered: 09/23/14
Posts: 1237
Loc: Toronto Canada
I have heard of this but never experienced it myself.

1.Disconnect the battery and hold the + and - leads together for a few seconds.
2.Simply give it more time

I am sure you do not need any special toolsl
Hope you didn't over apply any cleaner to the throttle body. You don't want cleaner in the motor/gears

Edited by WobblyElvis (12/07/17 03:02 PM)

#4597235 - 12/07/17 03:07 PM Re: '07 Suburban: post-TB clean idle woes [Re: Alex_V]
Alex_V Offline

Registered: 04/10/16
Posts: 1067
Loc: Campbellsville, KY
The guy that pulled the codes said he's sure it just needs relearned. He needed it this evening but it'll be back tomorrow for rear brakes so I'll do a proper re-learn then if it hasn't straightened itself out.
I like Chevy and Valvoline.

'13 Cruze, 1.4T, 110K
'85 GMC C3500, 454, 130K
'82 Mercedes 300CD, OM617 turbo, 165K
'67 Suburban, 350, 331K

#4597246 - 12/07/17 03:18 PM Re: '07 Suburban: post-TB clean idle woes [Re: Alex_V]
Throt Offline

Registered: 11/15/14
Posts: 902
Loc: NW Ohio
I know it's not a Ford but I've done this a few times and I know it does what he says it does because I've done it.
'18 Cadillac ATS AWD, 2.0L T-GDI, 200, Factor Fill/Filter, his (lease)
'17 Elantra, 2.0L, 15,500, QS Ult. 0w20 w/ FU, hers (lease)

#4597276 - 12/07/17 03:59 PM Re: '07 Suburban: post-TB clean idle woes [Re: Alex_V]
Merkava_4 Offline

Registered: 01/30/07
Posts: 17501
Loc: Clovis, CA
Originally Posted By: Alex_V
Any wisdom?

Yes. It helps if you remove all the sensors from the throttle body before you start cleaning it. GM uses a Tamperproof T20.

#4597283 - 12/07/17 04:12 PM Re: '07 Suburban: post-TB clean idle woes [Re: Alex_V]
yugrus Offline

Registered: 04/06/04
Posts: 431
Loc: ON, Canada
You should never open the throttle plate by hand if you don't have the scanner to follow the re-learn procedure. It is easier to have an assistant to open the plate by stepping on the pedal with key on, engine off, while TB is still on the car. This way you can clean the front, then remove the TB and clean the back. Get the shaft area good, so it doesn't stick. Clean as much of the intake as you can get, while there.
If the shaft isn't sticking, the idle will come down with time. Disconnecting the battery is another option, as previously suggested.
'14 Chevrolet Tahoe
'15 Mazda CX-5

#4597297 - 12/07/17 04:42 PM Re: '07 Suburban: post-TB clean idle woes [Re: Alex_V]
TmanP Offline

Registered: 10/30/15
Posts: 427
Loc: MN
My GM has a procedure to relearn the idle (after the battery is disconnected). I don't have the repair manual on me but it's so many seconds with the key on but the engine off, so many seconds with the engine running, then shut off.

I'd look for a similar procedure online, disconnect the battery and try again.
2006 Buick Lacrosse 3.8 V6 150,000 mi
2015 Chevy Silverado LT Z71 5.3 V8 30,000 mi
2010 Toyota Sienna 3.5 V6 150,000 mi

#4597462 - 12/07/17 07:34 PM Re: '07 Suburban: post-TB clean idle woes [Re: Alex_V]
LeakySeals Offline

Registered: 02/18/11
Posts: 6446
Loc: Hudson, NH
Sounds like the TPS. i replaced my TB a couple years ago for something similar. They are relatively cheap to shotgun if you want to Hitachi TB W/TPS

Clearing codes is fools gold. Doesn't fix the problem, doesn't make it go away. Makes it harder to fix a problem. Most codes will clear on their own when fixed. A relearn procedure should not be necessary if the engine is running good. When you reset power, it resets to factory original config. Should not be any noticeable changes if things are good. Learning is continuous and ongoing. So there is no point.
06 Escalade 6.0L AWD 155k. M1 EP 5w30 Fram TG
03 Maxima 3.5L Unknown miles ST 10w30

#4597836 - 12/08/17 08:19 AM Re: '07 Suburban: post-TB clean idle woes [Re: Alex_V]
GMBoy Offline

Registered: 11/22/04
Posts: 7664
Loc: Texas
Here is the relearn procedure you HAVE to do and with a Tech2 or similar high end scan tool:

Scan Tool Idle Learn or Idle Learn Reset Procedure Performed after the throttle body is cleaned or replaced
1. Ignition ON, engine OFF, perform the Idle Learn or Idle Learn Reset in Configuration/Reset or Module Setup.
2. Engine idling, observe the scan tool Throttle Body (TB) Idle Airflow Compensation parameter. The TB Idle Airflow Compensation value should equal 0% and the engine should be idling at a normal idle speed.
3. Clear the DTCs and return to the diagnostic that referred you here.

Edited by GMBoy (12/08/17 08:20 AM)