Engine and Tranny Issues - Update in OP

Disclaimer: Links on this page pointing to Amazon, eBay and other sites may include affiliate code. If you click them and make a purchase, we may earn a small commission.

rustycrocker

TYF Newbie
Joined
Jun 1, 2017
Posts
18
Reaction score
13
I have a 2007 Yukon XL with 160k miles. There are two issues:

Tranny hard shifts from 1-2. I replaced the 1-2 accumulator with a Sonnax pinless accumulator. It decreased the frequency of the hard shift, but it is still happening about 40% of the time. When I replaced the piston, there was only the small spring, the large spring was not installed. Ever seen this? I am considering replacing the Sonnax with the GM OEM accumulator, as it lasted 150k with no issues.

The engine (LMG 5.3 Flex) has a very rough idle, but cleans up around 1500 RPM. There are two codes showing:

P0449 (EEC vent valve solenoid). I replaced the solenoid with with no improvement. Clear the code and it comes back.

P0308 (Cyl 8 misfire). I suspect this is the AFM (Chevy shake).

Anyone care to comment?

TIA

Update 1/2/2023

Cleaned MAF with no improvement. Checked MAF with code reader and 5-6 on idle and 20-23 on acceleration. Pretty close to specs, so MAF is OK. Changed plugs and plug wires. BAM!! No more shudder, tranny shifts great. Looks like that was the issue.

Still have one code, P0499 - Evap Cannister Purge Solenoid. I have replaced the solenoid with no improvement. Maybe the PCM or the wiring?
 
Last edited:

Dustin Jackson

Full Access Member
Joined
Aug 9, 2018
Posts
1,402
Reaction score
1,545
With a transmission that old it might just be worn and due for a rebuild, I wouldn't bother throwing parts at it just drive it until it stops driving and then rebuild it.

I don't think cylinder 8 is an AFM cylinder, I think 1,4,6,7 are the AFM ones
 

Dustin Jackson

Full Access Member
Joined
Aug 9, 2018
Posts
1,402
Reaction score
1,545
@rustycrocker It's totally possible a non-AFM cylinder had a lifter failure. The lifters are just held in with plastic trays. To save money you can tear the engine down yourself to find the problem.
 
OP
OP
R

rustycrocker

TYF Newbie
Joined
Jun 1, 2017
Posts
18
Reaction score
13
My intention is to replace the more inexpensive components on the Yukon (plugs, wires, coil and injector) and see what happens. Worst case, I will do a teardown, as my warranty has long been expired.

I just wanted to get a second opinion.
 

iamdub

Full Access Member
Joined
Apr 23, 2016
Posts
20,752
Reaction score
44,595
Location
Li'l Weezyana
I have a 2007 Yukon XL with 160k miles. There are two issues:

Tranny hard shifts from 1-2. I replaced the 1-2 accumulator with a Sonnax pinless accumulator. It decreased the frequency of the hard shift, but it is still happening about 40% of the time. When I replaced the piston, there was only the small spring, the large spring was not installed. Ever seen this? I am considering replacing the Sonnax with the GM OEM accumulator, as it lasted 150k with no issues.

The engine (LMG 5.3 Flex) has a very rough idle, but cleans up around 1500 RPM. There are two codes showing:

P0449 (EEC vent valve solenoid). I replaced the solenoid with with no improvement. Clear the code and it comes back.

P0308 (Cyl 8 misfire). I suspect this is the AFM (Chevy shake).

Anyone care to comment?

TIA

Ever cleaned the MAF sensor?
 

Forum statistics

Threads
129,170
Posts
1,811,531
Members
92,258
Latest member
bcupp4086
Top