December 2023 - 18

Looking at Figure 6, you can see in the
top row (green and red traces), that I
adjusted the RPM and VSS Y-axes so
that the WOT segments paralleled each
other demonstrating the lack of torque
converter slippage.
Since I was preparing for this article, I
decided to connect the Ford factory tool
(IDS) to have a look at what their scan
tool offered to confirm my suspicions that
the torque converter clutch (TCC) was
slipping. Figure 7 shows us that indeed
the TCC is slipping.
In conclusion, the Ford Edge with only
44,000 miles will be visiting the dealer
for warranty work. The scan tool provided
us enough information with generic data
to conclude that the engine performance
was nominal, and the symptoms were
caused by a slipping torque converter
clutch. Additionally, if you look at the
middle traces in Figure 6, you can see
the wide band sensor is reporting lambda
(Wide Band Bank 1) closely following the
equivalence ratio command (EQ) during
a WOT event in power enrichment (PE)
mode. These numbers are indicative of a
healthy system and validate that several
systems are operating properly such as:
* Low-pressure fuel delivery
* High-pressure gasoline direct injection
* Turbo operation
* Proper cylinder air flow estimation
(airmass)
CASE STUDY #2:
COMEBACK - 2006 TOYOTA TACOMA V6 - P0171 P0174
We recently had a vehicle come in for multiple misfire DTC
which ended up needing coils and plugs to rectify. The technician
performed a road test and found that the vehicle's performance
was nominal. The problem is that a proper road test
with data analysis was not performed. The vehicle returned a
week or so later with a complaint that the MIL was on and that
there was some " pinging " that could be heard coming from
the engine under light load operation. However, the client did
state that the vehicle was no longer misfiring.
I proceeded to acquire some of the key performance data
parameters I typically record during a road test after seeing
that DTCs P0171 and P0174 were set. During my road test, I
observed light detonation occurring while driving. Then as
part of my normal road test procedure, I performed a WOT
pull making sure that I was able to sweep from 3,000 to 5,000
18 PTEN DECEMBER 2023 www.VehicleServicePros.com
p Figure 8 - 2006 Tacoma poor performance: P0171, P0174
Photo courtesy of Scott Brow
p Figure 9 - 2006 Tacoma after MAF sensor cleaning
Photo courtesy of Scott Brow
RPM noting that this engine produces maximum torque at
approximately 4,000 RPM. The significance of this RPM
point is that this is where the engine will achieve maximum
volumetric efficiency.
After returning to the shop, it was time again to analyze the
data. The data displayed in Figure 8 is very telling.
At 4,038 RPM, you can see the absolute load is at 60.4
percent which isn't good in my book. Additionally, since this
engine is equipped with two wide-band sensors, they are reporting
a lean condition across the entire WOT pull. Looking at
the MAF data along with my MAF Cyl Air6 math PID, I can
conclude that the air mass numbers are underreporting. See
my article titled " Solve driveability issues, emissions-related
failures with fuel trim diagnostics " from 2021 for more information
(VehicleServicePros.com/21241453).
The next step was to inspect the air flow tract to see if there
was anything that could be upsetting the MAF signal. Seeing
that there was none, we removed the sensor for inspection.
We could see clearly that the sensor was quite dirty, so we
attempted to clean it which on this vehicle isn't very feasible.
http://www.VehicleServicePros.com/21241453 http://www.VehicleServicePros.com
December 2023

Table of Contents for the Digital Edition of December 2023
