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I'm having engine surging problems too. ~160k, Automatic.

Customer Question
I'm having engine surging...

I'm having engine surging problems too

Mechanic's Assistant: How many miles are on the car? Is it an automatic or a manual transmission?

~160k, Automatic

Mechanic's Assistant: What is the model/year of your GM?

Yukon Denali / 2007

Mechanic's Assistant: Are you fixing your Yukon Denali yourself? What have you tried so far?

I've cleaned and reassembled the Mass Air flow sensor, made sure there were not leaks in the pipe

Mechanic's Assistant: Anything else you want the mechanic to know before I connect you?

The idle fluctuates, sometime is stalls in the driveway. Acts like it's in a lean condition.

Submitted: 8 months ago.Category: GMC
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Answered in 3 minutes by:
10/28/2017
GMC Mechanic: Ricardo Hohl, Master Certified Tech replied 8 months ago
Ricardo Hohl
Ricardo Hohl, Master Certified Tech
Category: GMC
Satisfied Customers: 4,343
Experience: Automotive instructor at Porter and Chester institute
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Hi welcome to just answers my name is Ricardo. Have you check for any pending codes in the system? have you check your charging system to make sure is sufficient charging this will also cause idle surge.

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Customer reply replied 8 months ago
Ricardo, it's not throwing any codes. Charge is good. Something in the fuel sensing system me thinks.
GMC Mechanic: Ricardo Hohl, Master Certified Tech replied 8 months ago

When no codes are present and the problem exist then its just an idle learn problem. The engine control module (ECM) learns the airflow through the throttle body to ensure the correct idle. The learned airflow values are stored within the ECM. These values are learned to adjust for production variation and will continuously learn during the life of the vehicle to compensate for reduced airflow due to throttle body coking. Anytime the throttle body airflow rate changes, for example due to cleaning or replacing, the values must be relearned. An engine that had a heavily coked throttle body that has been cleaned or replaced may take several drive cycles to unlearn the coking. To accelerate the process, the scan tool has the ability to reset all learned values back to zero. A new ECM will also have values set to zero.

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Customer reply replied 8 months ago
How much is an ECM anyway?
GMC Mechanic: Ricardo Hohl, Master Certified Tech replied 8 months ago

an ecm will need to be program to your vehicle and depending if new or remanufacture you be looking for no less then 500$

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GMC Mechanic: Ricardo Hohl, Master Certified Tech replied 8 months ago

lest try an idle learn procedure before you jump on to a computer replacement........... follow this procedure .1. Engine idling for 3 m. 2. The ECM will start to learn the new idle cells and the scan tool Desired Idle Speed should start to decrease. 3. Ignition OFF for 60 s. 4. Start and idle the engine for 3 m. 5. Verify the engine is idling normally. ⇒ If the engine idle is not correct Note: During the drive cycle the check engine light may come on with idle speed DTCs. If idle speed codes are set, clear codes so the ECM can continue to learn. 5.1. Operate the vehicle at speeds above 70 km/h (44 mph) with several decelerations and extended idles. 5.2. Verify the engine is idling normally. ⇒ If the engine idle is not correct. Ignition OFF for 60 s, repeat step 5.1. ⇓ If the engine idle is correct. 5.3. Clear any DTCs and return to the diagnostic that referred you here. ⇓ If the engine idle is correct 6. Clear any DTCs and return to the diagnostic that referred you here.

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Customer reply replied 8 months ago
Think I'll dink around w the sensors some more for that price!
GMC Mechanic: Ricardo Hohl, Master Certified Tech replied 8 months ago

yes lets do an idle learn follow the procedure step by step, you may have done this before but maybe you did not give the computer enough time to learn idle.

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GMC Mechanic: Ricardo Hohl, Master Certified Tech replied 8 months ago

if you clean the throttle and mass air flow then you definitely need an idle learn.

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Customer reply replied 8 months ago
I'll try pulling the ECM's fuse tomorrow, we'll see how that does
GMC Mechanic: Ricardo Hohl, Master Certified Tech replied 8 months ago

ok let me know tomorrow.

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Customer reply replied 8 months ago
Lobotomy relearn!
GMC Mechanic: Ricardo Hohl, Master Certified Tech replied 8 months ago

yes lol!!

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Customer reply replied 8 months ago
Still doing it, think it could be the TPS?
GMC Mechanic: Ricardo Hohl, Master Certified Tech replied 8 months ago

do you have a scanner to see the voltage on the tps sensor?

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Customer reply replied 8 months ago
Just a volt meter
GMC Mechanic: Ricardo Hohl, Master Certified Tech replied 8 months ago

you can use that also just back prove the tps connector harness and read the voltages on each wire let me know what they are looking for .65 volts

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Customer reply replied 8 months ago
Great to know, thx!
GMC Mechanic: Ricardo Hohl, Master Certified Tech replied 8 months ago

ok let me know what you get

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GMC Mechanic: Ricardo Hohl, Master Certified Tech replied 8 months ago

does this idle surge occurs at any temperature?

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Customer reply replied 8 months ago
Seems to happen more at op temp but still some at lo temps
Customer reply replied 8 months ago
Think the check balls in the valve body are shrunk too, just got it a month or two ago
Customer reply replied 8 months ago
Tranny guy's gonna pull pan and inspect the VB around Thxgvng
Customer reply replied 8 months ago
Sorry, don't mean to confuse you w 2 problems
Customer reply replied 8 months ago
I'm inclined to think it's the ECU, it does weird stuff, like open the rear door, lock the doors or actuate the seats uncommanded. There's another one on ebay for ~$150, finding out if it fits my VIN
GMC Mechanic: Ricardo Hohl, Master Certified Tech replied 8 months ago

Hi sorry for the delay any luck with the surge problem or you want to continue

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Customer reply replied 8 months ago
Pretty sure it's a bad gnd, added a gnd wire from body to alt bracket on drivers side, problem seems gone. These GMCs are notorious for it!
GMC Mechanic: Ricardo Hohl, Master Certified Tech replied 8 months ago

there should be 2 main grounds on this vehicle a body ground that connects the body to the engine and an engine ground that connects the engine to the battery , the body ground controls all the common grounds to the body and accessories and the engine ground controls ignition and fuel, if you have a poor engine ground problem the engine computer will be affected, if the ground works best when connected directly to the throttle control then this means the original ground to the ETC is missing or poor.

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Customer reply replied 8 months ago
Think it's poor, several guys on YouTube have vids on this subject, got a 24" gnd wire at PepBoys for $7, seems to have fixed it. Thx for your help anyway!
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