Solution K12034241
Friday, January 4, 2019 9:15:22 PM CET

Mack Models
Mack Model

CH , RB , DM , CHN , CL , CT , CV , CX , CXM , LE , MR , RD

** SOLUTION **
Title

Diagnosing Performance Complaints ASET Engine

Cause

General V-MAC information.

Solution

Performance Complaints can be difficult to diagnose, since they often are based on
comparisons to other units, or from a “seat of the pants” feel of the truck. There are
several types of Performance complaints, including Start ability (runs fine at higher rpm’
s), Stumble/Hesitation (usually around 1300 rpm’s), and overall low power.
As a starting point, ALWAYS make sure that the Customer parameters are set correctly
(Including Customer torque limit, and EUP calibration codes, etc).
There are several engine specific complaints that should be noted:

ASET AC ENGINES
• Boost Dropout
o On Step 4 equipped chassis, if the engine oil pressure drops below 15 psi, the
turbo vanes will open, and the truck will lose boost. This generally occurs during
take-off with a load, and can be diagnosed by monitoring the turbo vane position,
which will show a target AND actual value of zero. This condition will not throw
a code because the turbo is being COMMANDED to go to zero. Files are
available for SOME HP’s to correct this problem.
• Throttle lag after using the Engine brake
o This lag will occur on Step 3, 4 and 5 ASET AC equipped chassis’s when the
engine brake is not set up correctly in EECU Customer Parameters. Keep in
mind that on the newer trucks, there are two settings
Engine Brake installed
Powerleash Installed
• Flat at the “top end”
• Step 3 ASET AC engines were originally built with a 631GC5171 series
turbocharger. That turbo is no longer available, and has been replaced by the
5176 series of turbo. When changing from the 5171 to the 5176 turbo, the EECU
software and datafile must be changed to Step 3B or 3C. Failure to change the
software may result in 4-5 codes, and the truck feeling “lazy” in the upper rpm
range.

ASET AI ENGINES
• EUP BIP error

o Prevalent on Phase 4 AI engines with the Production Data file. This
phenomenon occurs when the EUP momentarily loses communication
with the EECU, and can be described as though you lifted your foot off
the throttle pedal, and immediately smashed it back to the floor.
Generally happens around 1400-1600 rpm’s. EECU Service files corrects
this problem.

NOTE:
These troubleshooting steps were written with the assumption that
BASIC checks, such as monitoring fuel pressure, has already been
done and ruled out as a possible cause.

1) How long has the Customer complained about power
a. Since New:
i. Is the EECU service file loaded?
o Under NO circumstances should NOx Levels be crossed
ii. Is the VECU at Step 12B
• Step 12 can only be installed in an M6 VECU module

NOTE: If in doubt, reference the Software/Data file spreadsheet to determine the
correct Service files for download
iii. Does the Customer own more than one truck
• What is he comparing to
Many Performance complaints are based on comparisons of EGR to NonEGR equipped trucks, or comparisons to a different OEM. These comparisons
are unacceptable.
• If the Customer has the same complaint about multiple units from new, the
DSM should be notified as this may be a spec issue.
iv. Is the truck being shifted correctly
1. Shifts being made at an rpm which keeps the truck within it’s operating
range
v. If the complaint persists with the latest files, have the Tech contact his DSM to
further pursue the complaint, and possibly have the truck run on a dyno.
b. Recent Complaint
i. Are any codes logged
1. If Yes, Troubleshoot per the Published Service information
ii. Are there other symptoms
1. Does the truck smoke
a. If yes, what color is the smoke
i. Black smoke
• Has the Intake system been checked for leaks
• Have the injectors been tested/cleaned
• If so equipped, is the EGR system functioning properly
ii. White smoke
• Is there an EECU Service file available
• Is the Customer using good fuel

• Have the engine speed sensors been checked
iii. Bluish smoke
• Is there oil in the intake
a. Possible turbo failure
• Has the compression been checked (Manual test)
2. Does the truck backfire
a. Have the valves been adjusted
b. Does the truck have an engine brake
i. Is the brake sticking on
1. Follow powerleash diagnostics
3. Does the truck Hesitate/stumble
a. Is the EECU Service file loaded (AI Engines)
iii. Has the boost pressure been checked
1. If the boost is low
a. Are there any restrictions in the intake or exhaust
i. Clogged air filter
ii. Intake hose “sucking” shut when hot
iii. Kinked exhaust/plugged muffler
2. Is the hood boot sealing correctly
a. Spread grease around the rubber boot and close the hood.
When the hood is raised, the grease should have transferred to the hood in a
complete circle.
3. Verify the correct Turbocharger is installed
4. Is the Engine equipped with a boost pressure relief valve or an air cleaner
scavenger
a. Have they been tested, and are they functioning properly
5. Pressure test the entire intake system a. Fix any leaks found
6. Inspect the exhaust manifold and the turbo center section for cracks
a. In most cases of a turbo whistle or whine, the noise is gasket
related
7. Inspect the compressor wheel for proper clearances with the housing
a. In rare cases, the wrong compressor wheel has been found
installed in ASET AC turbo chargers
i. Easily noticeable, with a large gap around the
compressor wheel
8. Test the boost pressure sensor (Key on/Engine off reading should be under 1
psi)
iv. What is the Pyrometer reading
1. High (Over 1100)
a. Have the valves been adjusted

b. If available, use an IR temp gun to check each cylinder to isolate
possible cylinder problems
c. Test/clean the Injectors
d. For AC engines, check the compressor discharge temperature and
the hood boot seal
e. Check the EGR system for proper operation
2. Low (Under 800)
a. Test/clean the Injectors
b. If available, use an IR temp gun to check each cylinder to isolate
possible dead cylinder
v. Is the truck going into De-rate 1. Overheating
2. Out of range sensor value
a. Compressor discharge temp
b. Turbo wheel speed
c. Pyrometer

Disclaimer:
This outline does not take into account non-engine systems which may also cause low
power complaints, such as the fan drive, the clutch slipping, Service brakes hanging up,
etc. If nothing Mechanically wrong is found, The information should be forwarded to
Reliability Engineering to determine if the truck qualifies for any further file
advancements (determined on a case by case basis, taking into consideration each states
emissions laws, and file availability based on HP). The Technician should also contact
his DSM to verify the complaint, and determine if a Dyno run is required.

NOTE:
In order for a dyno run to be deemed acceptable, the truck must be run in direct
(transmission gear = 1), the dyno report must denote if the fan was on or off, and at a
minimum, must show rpm’s and road speed for each HP reading.
Solution visibility

Dealer distribution

Administration
Author

A241298

Dealer ID

A241298

Last modified by

A241298

Creation date

31-12-2018 15:12

Date of last update

31-12-2018 18:12

Status

Published