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2010 Suburban 75th Diamond Edition
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Discussion Starter #1 (Edited)
I have a 2010 Suburban 75th Diamond Edition with 140K miles.
Platform GMT931, Engine: 5.3 L (325 cu in) Vortec 5300 LMG flex fuel V8, Trans: 6-speed 6L80 automatic.

The problem I am having is that the car does not run smooth.

Here is a list of the symptoms that I am experiencing. The strange things is that there are no codes being thrown..
  • In Park the car seems to idle rough. The idle hovers right above 500rpm, and moves up a little bit then down a little bit. Sometime I think I feel a stumble.

  • When the car is in Drive but not moving the idle drops to 500rpm and I feel/hear a rumble/vibration/groan that is not present when the car is in Park. While in Drive does not idle perfectly at 500rpm, it will dip down slightly below 500rpm and recover to 500rpm sporadically.

  • Sometimes the car will accelerate when braking. For example.. While driving, then braking to come to a stop, the car sometimes will surge while braking. When this happens I will need to apply more braking force to stop the car. It has scared my wife a few times when it does it to her.

  • Sometimes the car will seem to power itself and accelerate on it's own. At around 1K to 1500rpm, at about 15 to 20mph the car sometimes will seem to power it self and maintain the speed as if I was giving the car gas... Sometime when starting the car the idle will seem a little high, and if I put the car in Drive, and release my foot of the brake, the car will start moving forward and and accelerate to about 5 to 8 mph...

  • Sometime the car will briefly hesitate to accelerate from a stand still.

  • Once recently, 2 yellow lights started flashing on the dash as if I were loosing traction.. I was accelerating from a stop sign at a regular pace, the car did not loose any traction or spin the tires but lights on the dash blinked at me as if I was spinning out or something. This happened at around 10 to 15mph... It only happened for a few seconds and went away. Like I said, this has only happened once, and I was in a construction zone where there was dirty and sand on the road. So maybe the rear did actually loose traction.. But I swear I didnt feel anything and did not jump on the gas.... IDK...

  • Sometimes there seems to be a hard shift between 1st and 2nd gear. I usually will notice this when I am traveling while the engine is cold, and on residential streets. Where as I am having to do a lot low speed driving in 1st and 2nd gears due to having to stop at all the stop signs. It's like the car doesn't know when to shift to second, and down shift back to 1st..

  • Sometimes when braking and right before the car stops,, at maybe 10 mph and the wait shifts I hear/feel a clank.

Here is a list of recent things that I have had done trying to fix the issue I listed above..
  • I have replaced all 3 motor mounts with OEM mounts

  • New plugs and wires OEM

  • Throttle body cleaned and fuel injector service by dealer.

Car still has the issues I listed.

The dealer and the mechanics I talk to seem to be lost since the car does not throw any codes.

Are there any test I can request to be done that might point me in the right direction?

I have seen people mention on various forums about potential fixes... idle relearn, ecm reprogram, replace the throttle body, replace the MAF, rebuild the engine due to AFM issues, etc..

I am located in the Dallas Fort Worth Metroplex, is there a mechanical of shop that is recommended to hunt down and repair these types of issues?
 

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I don't know the 5.3, I don't know all the AFM nuances, and I don't know the 6 speed trans, but a lot of those symptoms sound like the old problems found in the 4L60E trannys. You might take it to a good trans shop and have them hook up the scan tool and take it for a ride to check pressures and shift points.
 

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2010 Suburban 75th Diamond Edition
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Discussion Starter #3
I don't know the 5.3, I don't know all the AFM nuances, and I don't know the 6 speed trans, but a lot of those symptoms sound like the old problems found in the 4L60E trannys. You might take it to a good trans shop and have them hook up the scan tool and take it for a ride to check pressures and shift points.
Is there a particular type of scan tool that is need to perform this type of test? I am going to call around to some transmission shops tomorrow..
 

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Discussion Starter #4
Here is document I found talking about testing the MAF and the TPS sensors..

What test could I have done that will plot the readings of the MAF and TPS? Is there a certain type of diagnostic I should ask for?

When I ask the service advisor at the dealer about running various test, they feel as if the tests will not come back and show anything because if the sensors where bad they say it would throw a code. Are dealers the only people that have these special computers that can read individual sensors?

If I have a test ran will they give me graph printout that show the output of those sensors so that we can see exactly what is being output by those sensors?

Also what what type of Vacuum test should be ran to check if there is a vacuum leak causing these issues?
 

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Try to run it in V8 mode all the time and see if it will fix the shifting issue. You can do this by putting the transmission in M5 or L5 whichever applies. I used to have a 2011 Silverado and it clunked when it transitions from V4 to V8 in slow speeds. When going thru town at slow speeds up to 45mph, I always shift it in M5. Or you can disable the AFM with a Range or Diablosport AFM delete that plugs in to the OBD2 port and run in V8 full time.

Are you using Mobil1 5W/20 Dexos full synthetic oil since new? This is the approved oil type for this AFM engine. AFM engines don't like sludge.

As far as testing the MAF or TPS, you can get a scanner that plugs in to the OBD2 port and can read live data and just plot the values at 500 rpm increments. It has to be a linear rise with no abrupt increase or loss of value.
 

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It sounds to me like a problem between the gas pedal (accelerator position senso) and the throttle body (throttle position sensor).

I'm thinking the TPS is not correctly following the APS.

The TPS, on your truck, is covered under an extended warranty, I'd talk to a service manager about the problem.
 
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I would also check the battery cables as some of these trucks had failures at the connecting points due to water intrusion/looseness and corrosion. Check the fuse box too for loose connections and loose fuse/relays.
 

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Discussion Starter #8
Try to run it in V8 mode all the time and see if it will fix the shifting issue. You can do this by putting the transmission in M5 or L5 whichever applies.... Or you can disable the AFM with a Range or Diablosport AFM delete that plugs in to the OBD2 port and run in V8 full time.
Will give this a try, and report back my findings!

Are you using Mobil1 5W/20 Dexos full synthetic oil since new? This is the approved oil type for this AFM engine. AFM engines don't like sludge.
I think I have been running 5w 30 full synthetic.. Not 100% sure if I have only been using mobile 1. I have a Mobil 1 Lube Express about 10 minutes away from me. I can run by there today and have them do a new oil and filter change. Should they have the Mobil1 5W/20 Dexos full synthetic there? Would you recommend I add any type of additive (lucas/stp) to the oil?

As far as testing the MAF or TPS, you can get a scanner that plugs in to the OBD2 port and can read live data and just plot the values at 500 rpm increments. It has to be a linear rise with no abrupt increase or loss of value.
Got to love Amazon. I just logged in and purchased the BlueDriver Bluetooth Pro OBDII Scan Tool for iPhone & Android. It says it will be delivered today by 6pm.
 

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Discussion Starter #9
It sounds to me like a problem between the gas pedal (accelerator position senso) and the throttle body (throttle position sensor).

I'm thinking the TPS is not correctly following the APS.

The TPS, on your truck, is covered under an extended warranty, I'd talk to a service manager about the problem.
Is the APS something I can plot using the ODBII Scanner?

Can you give me more detail regarding the TPS being covered by an extended warranty? Any links to an official TSB or GM Press release that I can provide to the service advisor?

Thanks!
 

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Try YouTube, lots of vids on testing using a multimeter
 

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Discussion Starter #11
Try YouTube, lots of vids on testing using a multimeter
Can you give me more detail regarding the TPS being covered by an extended warranty? Any links to an official TSB or GM Press release that I can provide to the service advisor?
 

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Discussion Starter #12
So I am looking over the features available in the OBDII Scanner I ordered.

For my vehicle the BlueDriver Pro OBDII Scanner supports live data & graphing for the following.
  • Fuel system status
  • Calculated LOAD Value
  • Engine Coolant Temperature
  • Short Term Fuel Trim - Bank 1 / Bank 3
  • Long Term Fuel Trim - Bank 1 / Bank 3
  • Short Term Fuel Trim - Bank 2 / Bank 4
  • Long Term Fuel Trim - Bank 2 / Bank 4
  • Fuel Rail Pressure (gauge)
  • Intake Manifold Absolute Pressure
  • Engine RPM
  • Vehicle Speed Sensor
  • Ignition Timing Advance for #1 Cylinder
  • Intake Air Temperature
  • Air Flow Rate from Mass Air Flow Sensor
  • Absolute Throttle Position
  • Bank 1 - Sensor 1
  • Bank 1 - Sensor 2
  • Bank 2 - Sensor 1 / Bank 3 - Sensor 1
  • Bank 2 - Sensor 2 / Bank 3 - Sensor 2
  • Time Since Engine Start
  • Distance Traveled While MIL is Activated
  • Commanded Evaporative Purge
  • Fuel Level Input
  • Number of warm-ups since DTCs cleared
  • Distance traveled since DTCs cleared
  • Evap System Vapor Pressure
  • Barometric Pressure
  • Catalyst Temperature Bank 1, Sensor 1
  • Catalyst Temperature Bank 2, Sensor 1
  • Control module voltage
  • Absolute Load Value
  • Fuel/Air Commanded Equivalence Ratio
  • Relative Throttle Position
  • Ambient air temperature
  • Absolute Throttle Position B
  • Accelerator Pedal Position D
  • Accelerator Pedal Position E
  • Commanded Throttle Actuator Control
  • Alcohol Fuel Percentage

So out of that list, what all should I graph that may lead to figuring out what is going on with my car?
 

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Discussion Starter #13
So I have received my OBD Scanner and drove about 20 minutes..

I am currently in the process of analyzing the data.

1st thing I am looking at is the Accelerator Pedal Position D (%) and the Accelerator Pedal Position E (%) data.

According to the info I found (https://mechanics.stackexchange.com...rator-pedal-position-d-and-e-sensors-on-obdii). If you take D and divide it by E you should get a quotient of 2.

For the most part, I am getting the quotient of 2.04 when I divide D by E..
But I am seeing some fluctuating quotients as low as 1.28 and as high 3.29.

So do you all think this data warrants replacing the Accelerator Pedal Position Sensor (ACDelco 25832864)?

Here is a link to the part Amazon.com: ACDelco 25832864 GM Original Equipment Accelerator Pedal with Position Sensor: Automotive
 

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Which component reading is jumping around to alter the final equation value? I would start by pulling that particular item, checking connections/grounds, cleaning it (if possible), and retesting.
 

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Discussion Starter #15
Which component reading is jumping around to alter the final equation value? I would start by pulling that particular item, checking connections/grounds, cleaning it (if possible), and retesting.
The Accelerator Pedal Position Sensor is 1 sensor but has 2 outputs for failover. 1 output is half the signal strength of the other. So when the sensor is working correctly you should be able to take output 1 from the APP at a given time, and take output 2 at that exact same time, divide them and the quotient should be 2.

So when the ECM does not receivv the expected values from output 1 and output 2, it can create a moment of strange things happening with idle, shifting, acceleration, etc...

Here is a youtube video of someone explaining this..
 

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Discussion Starter #16
Here is a graph of my APP output 1 and 2





Here is the quotient graph deduced from both outputs. From what I have learned, If the both outputs where outputting properly, I should have a straight line across the graph at 2.00. But you the can see the outputs are some times way out of sync..

 

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The Accelerator Pedal Position Sensor is 1 sensor but has 2 outputs for failover. 1 output is half the signal strength of the other. So when the sensor is working correctly you should be able to take output 1 from the APP at a given time, and take output 2 at that exact same time, divide them and the quotient should be 2.

So when the ECM does not receivv the expected values from output 1 and output 2, it can create a moment of strange things happening with idle, shifting, acceleration, etc...

Here is a youtube video of someone explaining this..
Ah, yes. My bad. I still had the 2 components on the brain and missed the double outputs.

I would still try cleaning the sensor and reseating connections first. Perhaps it's just corroded.
 

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The APPS is just a variable resistor, use an ohm meter to test it, it should change resistance smoothly.
 

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Discussion Starter #19
Today I took a look at the throttle position sensor.

Here is a graph of the output I got today while driving.
At idle 0mph, the absolute throttle position sits at about 16%.
What would cause those 2 dips that I have circled in red?
Does that indicate the tps is bad?
167633
 

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I'm not an expect; but I would guess your seeing the TPS input from the pedal position sensor.
As I said earlier, an ohm meter will tell you if the position sensor is smooth, or has open spots.
A new sensor is probably $40
 
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