Honestly, I have no idea. I have never worked on an automatic transmission. I'm just reading the documentation here! Maybe the valve spool or whatever gets sticky when warm or when there is fluid pressure against it?
Engine no acceleration
- Thread starter Uncleenvoy
- Start date
Honestly, I have no idea. I have never worked on an automatic transmission. I'm just reading the documentation here! Maybe the valve spool or whatever gets sticky when warm or when there is fluid pressure against it?
Well the deed is done..gonna clear the code drive it around and hope its good..if not ill take out the valve body and change the valve thing in the hole
JayArr
Member
Change them anyway. The code occurs if the PCM sees a 4-3-3-4 shift pattern. It sets if both conditions are met.
Condition 1: PCM commands first gear for 2 seconds - estimated gear ratio is 0-1.4
Condition 2: PCM commands second gear for 1 second - TC efficiency os 0.5 or more and gear ratio is 0.9-1.2
Basically if you can't get first or second gear to work.
INSPECT:
Debris or chips in the AFL (actuator feed limit) oil passage
Debris or chips in the #29 passage of the case or through the spacer plate gasket into the valve body. (entrance to 2-3 shift sol valve bore)
Cracked 2-3 shift solenoid
2-3 shift valve stuck or hung up in the body
2-3 shuttle valve stuck or hung up in it's bore.
Damaged shift solenoid seals
If I'm reading the hydraulic schematic correctly the 2-3 shift valve and 2-3 shuttle together decide if you can have gears 1&2 or 3&4. It should be forced all the way to the end of the bore by the AFL line pressure in first or second gear and the solenoid cuts off that pressure for third and fourth gear and the springs push the valve and shuttle out.
Can you pull the 2-3 shuttle and the valve out, make sure there is no debris and make sure it is all assembled correctly with all of the required springs?
Since it's all hinged on proper AFL line pressure you may want to pull and check that it was correctly assembled as well.
Jeff
Condition 1: PCM commands first gear for 2 seconds - estimated gear ratio is 0-1.4
Condition 2: PCM commands second gear for 1 second - TC efficiency os 0.5 or more and gear ratio is 0.9-1.2
Basically if you can't get first or second gear to work.
INSPECT:
Debris or chips in the AFL (actuator feed limit) oil passage
Debris or chips in the #29 passage of the case or through the spacer plate gasket into the valve body. (entrance to 2-3 shift sol valve bore)
Cracked 2-3 shift solenoid
2-3 shift valve stuck or hung up in the body
2-3 shuttle valve stuck or hung up in it's bore.
Damaged shift solenoid seals
If I'm reading the hydraulic schematic correctly the 2-3 shift valve and 2-3 shuttle together decide if you can have gears 1&2 or 3&4. It should be forced all the way to the end of the bore by the AFL line pressure in first or second gear and the solenoid cuts off that pressure for third and fourth gear and the springs push the valve and shuttle out.
Can you pull the 2-3 shuttle and the valve out, make sure there is no debris and make sure it is all assembled correctly with all of the required springs?
Since it's all hinged on proper AFL line pressure you may want to pull and check that it was correctly assembled as well.
Jeff
Looks like we did it fellas..drove 8 miles up and down my normal test route and all is good..condition was usually occurring at around 3 miles of driving..gonna throw on that new abs sensor and drive her some more then torque up all those bolts underneath if no further problems..p0017 is pending again though..and it was in the list of codes along with the p0756 that i just cleared so gonna pull that sensor and see whats the story there
@gmcman Those were the original ones..i think you were the one that was telling me to check those when i first started..shoulda listened..but not that hard a job probably 10 mins remove 20 mins replace..loving those new milwaukee power tools..abs sensors are in..no light no activation at every stop sign..drove another 4 miles and all is good..few minor things to take care of..passenger revrse bulb blown and replace that sheild/bracket thing that goes in the side of the trans pan..and gonna check the price of a crank sensor to see if that gets rid of p0017..gonna take it on the highway later tonight so it can run all the diagnostic tests..the evap test never completed
Thanx buddy..im glad its done..gonna sign title over tonight after the highway run and tell em to come get it
If this Tool was not a Rental... when time permits, would you mind listing the Make-Model & Part Number? I'd like to get one exactly like it, as yours was well employed in this instance:
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JayArr
Member
I got mine as part of a front end service kit.
www.carid.com
It's available as a single item under part number OTC 7503 - Tie Rod/Inner Bearing Race Puller Remover.
OTC® 6295 - 5-piece Front End Service Set
Universal 5-piece Front End Service Set - Part Number 6295 by OTC. This set is designed to remove and install press-fit upper and lower ball joints. Automotive Tools.
It's available as a single item under part number OTC 7503 - Tie Rod/Inner Bearing Race Puller Remover.
Wow..they want 55bux for that and you can get the whole kit for 100..saw a whole kit on ebay for 33bux
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Funny thing is i didnt know what it was called but i know what needed and that ive seen it before..turns out i rented the kit b4 but didnt use that particular tool..so im trying to explain ti the guy "the thing with the threaded bolt and the clamps at an angle not the straight clamps not the adjustable clamps" and so on..he got fed up and sais just come in the back and look for it..and there it was 5 piece front end service kit..130bux to rent
JayArr
Member
Have a real good look at your exhaust between engine and the O2 sensor. Any exaust leak there will cause the O2 sensor to see a (false) lean mixture.
How an Exhaust Leak Affects Wideband/O2 Sensor Readings
We drill holes in an exhaust header to demonstrate how even the tiniest exhaust leak can affect O2 sensor accuracy and yield unreliable tuning data.
Also, check the rubber hoses on the fuel fill for cracks-just happend to me (for the P171), had to replace the fuel fill assy, couldn't find just the rubber hose.
This MAF looks its seen better days..is this what one typically looks like when functioning properly? i dont have one on the envoy to compare it to..and also this hose isnt flush agaisnt the bottom there..is that enough to let in air?
Attachments
The P0171 Code can sometimes have a specific source for allowing Secondary Air to keep getting into the Exhaust Stream and FUBAR the sought out Stoichiometric of 14.7:1 perfection with the Upstream O2 Sensor if the SAIS Solenoid STICKS OPEN (Circled in Blue on the Diagram). It will be an E-Z R&R if this proves out to be the 'problematic part':
This Lengthy Video goes into the Technical Diagnostics needed to isolate the SAIS Pump Solenoid based upon LT-ST Fuel Trim Readouts:
This Lengthy Video goes into the Technical Diagnostics needed to isolate the SAIS Pump Solenoid based upon LT-ST Fuel Trim Readouts:
@MRRSM ive dealt with that secondary check valve b4 in my envoy many years ago..thats actually what got me into doing repairs on my car..i was buying a new air pump every year to pass inspection..finally decided to look into it myself when the mechanic wouldnt or couldnt explain to me why my air pump is fiiled with water every year..fixed it myself and ive been on this journey ever since..guess he wanted that 400bux or whatever i was paying every year..that being said, shouldn't i get a p0410 as well then..i think thats the sec air code
Not if the SAIS Pump is functioning properly. This "Sticking" Solenoid is a "Mechanical Malfunction" with the Solenoid being "The Last SAIS System Component" that deals with controlling the Air Stream prior to its final entry into the Exhaust Stream.
What you are looking for is its actual actuation of the Internal Baffle...which may...or may NOT work when fed 12 Volts DC to the Solenoid. Please remember to use ONLY Momentary Electrical Surges with it fixed in place (Bench Vise) and try NOT to overheat the Solenoid in this manner.
Just know that even if the Solenoid appears to respond nominally "On The Bench" ...its sketchy behavior may only manifest itself while it is bolted up to the Passenger Side of the Motor-Head.
As @BrianF suggests... with an Aging SUV you could have more than one component sharing a Common Bad Result with the common denominator being that BOTH play a part in managing "AIR" through this LL8 Engine. :>)
Just know that even if the Solenoid appears to respond nominally "On The Bench" ...its sketchy behavior may only manifest itself while it is bolted up to the Passenger Side of the Motor-Head.
As @BrianF suggests... with an Aging SUV you could have more than one component sharing a Common Bad Result with the common denominator being that BOTH play a part in managing "AIR" through this LL8 Engine. :>)
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@gmcman checked that hose already and its in there good..ill pull it off and see if it has any holes in it though.. and i torqued those intake mani bolts when i put it back on a few weeks ago..ill double check that last one near the firewall though..i think i tighted it but didnt hear the click sound on the torque wrench and was concerned to go any more as i didnt want to snap the bolt..that one would be a nightmare to get out if snapped
Is there a port or location where i can just hook up that vacum gauge i bought to test the vacuum in the system
If seal off the air intake side of the box with a plastic golve or something and create vacuum from somewhere else?
Thess MAFs are expensive..45bux cheapest ive seen locally..and that one isnt really local its in jersey..rock auto has one for 23bux think ill do that..put back in the cleaned old one see if that helps and continue to look for leaks
gmcman
Member
- Dec 12, 2011
- 4,656
Just a friendly fyi, be careful using a torque wrench in tight areas, easy to choke down on the wrench and not hold the handle.
A torque wrench is only accurate when you apply force at the handle, if you hold your hand farther down towards the socket, it will apply more torque than set for.
Safe bet the MAF is likely the issue.
Gonna go grab a new can of electrical cleaner and give a good cleaning..after this im done..transfered title yesterday and told him anything after this they gonna have to pay for..im gonna eat the maf cost cause the light came on literally 10 minutes b4 he came for keys and title..told em ill pay for reverse bulbs and air filter but ill buy the maf as well and thats it
THIS is the only recommended cleaning solvent specifically made by CRC for cleaning that delicate MAF Sensor "Bulb". Recently, I saw a video of ScannerDanner working on a Late Model GM Silverado at his Brother's Garage manually cleaning the MAF Sensor "Bulb" with a very small brush while also using only the CRC MAF Spray Solvent ...and it worked great... But he was being VERY careful with its application though:
Here he is explaining his Abbreviated, Universal "How to Diagnose a P0171 involving cleaning issues with the MAF Sensors":
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Here he is explaining his Abbreviated, Universal "How to Diagnose a P0171 involving cleaning issues with the MAF Sensors":
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