10. Install Transmission Adapter and
Flexplate. Refer to Flexplate and
Transmission Adapter Replacement.

11.

11. Using an approved hoist and proper
lifting hardware, install Engine in
vehicle using Main Accessory Drive
Bracket (7) Lift Point (6). Figure 3

12.

12. Install Front Engine Mount to vehicle
frame. Refer to Front Engine Mount
Replacement.

13.

13. Connect LPI® Fuel Supply and Return
Lines. Refer to Fuel System Torque
and Tightening Specifications.

15.

DSM.0052 Ver. 1.0 05/27/2022

7

3.

4.
5.
6.

6

Figure 3:
Engine Lift Point (7) on
Main Accessory Drive Bracket (6)

488LPI Propane Autogas Engine Mechanical
and Fuel Components Service Manual

Page 47 of 117

14. Prior to installing the upper intake
manifold the fuel system will need
to be checked for leaks. To check
the for leaks the supply solenoid must
be energized to allow fuel to flow and
pressurize the fuel system.
 Open the supply and return valves.
 Disconnect supply valve solenoid
harness from tank harness Figure
4
 Energize solenoid using a power
probe or similar tool. An audible
click should be heard indicating the
solenoid has opened.
 Once the system is pressurized
spray each hose connection with
an approved leak check solution
and look for bubbles around each
hose connection.
 If any leaks are found, retighten
hoses and leak check again.
15. Install Upper Intake Manifold. Refer to
Upper Intake Manifold Replacement.

Figure 4:
Disconnect supply solenoid harness (arrow)
from tank harness and energize solenoid with
12 volts.

16.

16. Install Alternator. Refer to Alternator
Replacement procedure.

17.

17. Install Engine Harness on Engine.
Refer to Engine Harness
Replacement.
18. If equipped: Install Air Conditioning
Compressor Bracket. Refer to Singleor Dual-A/C Drive Bracket
Replacement.

18.

19. If equipped: Install Air Conditioning
Compressor(s). Follow OEM
procedure.

20.

20. If equipped: Install Air Compressor.
Refer to Air Compressor
Replacement.
21. Install Main Accessory Drive Belt.
Follow OEM procedure.

21.

DSM.0052 Ver. 1.0 05/27/2022

19.

22.

488LPI Propane Autogas Engine Mechanical
and Fuel Components Service Manual

Page 48 of 117

22. Install Oil Dipstick Tube. Follow OEM
procedure.
23. Install Air intake Tube. Refer to Air
Intake Tube Replacement.
24. Install Air Cleaner. Follow OEM
procedure.
25. Install vehicle Cooling Pack. Follow
OEM procedure.

23.

25.
26.

26. Secure vehicle on approved hoist and
raise vehicle.

27.

27. Connect Post-catalyst Heated Exhaust
Gas Oxygen (HEGO) sensors to
Engine Harness. Refer to OEM
procedure.

28.

28. Install Transmission. Follow OEM
procedure.

29.

29. Install Starter. Follow OEM procedure.
30. Install new Y-Pipe Gasket (4). Figure 5

30.
31.

31. Connect Y-pipes to Exhaust Manifolds
(5). Figure 5. Refer to Exhaust
Manifold Replacement.
32. Tighten Y-Pipe Hangers (not shown).
Follow OEM procedure.
33. Install Y-Pipe Assemblies (3). Follow
OEM procedure. Figure 5

3

34. Lower vehicle.
35. Fill Engine Coolant. Follow OEM
manual for capacity and procedure.
Refer to 488LPI™ Owners Manual for
coolant specifications.
36. Check Engine Oil Level and top off if
necessary. Refer to 488LPI™ Owners
Manual for procedure and
specifications.

1

5

4

2

Figure 5:
Y-Pipe Assembly (3), Y-Pipe Gasket (4),
Exhaust Manifold Heat Shield (5),
Exhaust Manifold (1), and Nut (2)

37. Check Transmission Fluid Level and
Quality. Follow OEM procedure.
38. Clean any spilled fluids.

40.

39. Install vehicle Hood. Follow OEM
procedure.

DSM.0052 Ver. 1.0 05/27/2022

488LPI Propane Autogas Engine Mechanical
and Fuel Components Service Manual

Page 49 of 117

40. Turn LPI® fuel supply and fuel return
Manual Shutoff Valves to OPEN
position.
Manual Shutoff Valves must always
be fully open for engine operation
or warranty will be void.
41. Verify proper operation.
42. Follow Engine Break In Procedure as
required by 488LPI™ Owners Manual.

DSM.0052 Ver. 1.0 05/27/2022

41.

42.
43.

488LPI Propane Autogas Engine Mechanical
and Fuel Components Service Manual

Page 50 of 117

Exhaust Back Pressure Test
DESCRIPTION AND OPERATION
Perform an Exhaust Back Pressure Test if a vehicle powered by the 488LPI™ engine exhibits the
following symptoms:
 Misfire Diagnostic Trouble Codes (DTCs) SPNs 1323-1330 FMI 31 OR
 Mass Air Flow (MAF) Sensor DTCs SPN 132 FMIs 2, 3, 4 or 7 AND/OR
 Low power on acceleration

In some cases, an over-fueling condition resulted in high exhaust back pressure causing
the Catalytic Converter(s) to clog and fail. Therefore, this possibility, (if applicable) can
and should be assessed to prevent repeat Catalytic Converter failures. Check both fuel
system and ignition system components, wiring, and controls.
TEST PROCEDURE
1. Secure vehicle on an approved
hoist and allow engine to cool.
2. Raise vehicle.
3. Remove driver side Pre-Catalyst
Heated Exhaust Gas Oxygen
(HEGO) Sensor. Refer to HEGO
Replacement.
4. Install Adapter Fitting in head pipe
HEGO Sensor Bung.
5. Connect Exhaust Back Pressure
Gauge to Adapter Fitting.
6. Lower vehicle
7. Start engine. Have an assistant
record exhaust back pressure
readings at all engine speeds
specified in Table 1.
8. Remove Exhaust Back Pressure
Gauge and Adapter Fitting.
Adapter and Gauge Connection
may be hot.

9. Install Pre-Catalyst Heated Exhaust
Gas Oxygen (HEGO) Sensor. Refer
to HEGO Replacement.
10. If exhaust back pressure readings
exceed normal levels listed in
Table 1 AND vehicle exhibited low
power on acceleration, go to Step
11.
11. Repeat Steps 2 through 9 for
passenger side Pre-Catalyst Heated
Exhaust Gas Oxygen (HEGO)
Sensor.
Normal Exhaust Back
Pressure Ranges
Engine RPM
PSI
kPa
Idle

1.25

8.6

Throttle Snap

3.0 4.0

20.7 27.5

2,000

0.5

3.4

2,500 (sustained)

02.0

013.7

Table 1:
Normal Exhaust Back Pressure Values

DSM.0052 Ver. 1.0 05/27/2022

488LPI Propane Autogas Engine Mechanical
and Fuel Components Service Manual

Page 51 of 117

Exhaust Manifold Replacement
REMOVAL PROCEDURE
1. Secure vehicle on a approved hoist
and raise vehicle.
2. Driver side: remove three (3) Nuts (2)
securing Y-Pipe Assembly (3) to
Exhaust Manifold(s) (1). Figure 1
3. Passenger side: remove three (3) Nuts
(2) securing Y-Pipe Assembly (3) to
Exhaust Manifold(s)
4. Remove Y-Pipe Gaskets (4) and
discard. Figure 1
5. Loosen Y-Pipe Hanger (not shown) at
Transmission. Follow OEM procedure.
6. Lower vehicle and open hood.
7. NOTE: Passenger side manifold only.
Remove Oil Dipstick Tube. Follow
OEM procedure.
8. NOTE: Passenger side manifold only.
Remove Air Cleaner Assembly. Follow
OEM procedure.
9. NOTE: Driver side manifold only, and if
equipped: Remove Air Compressor.
Refer to Air Compressor Replacement.
10. Remove Spark Plug Wires.
Twist Spark Plug Boot 1/2-turn to
release boot. Pull on Spark Plug Boot
only; do not pull on Spark Plug Wire
or risk damage.
11. Remove Spark Plugs (not shown).
12. Remove Exhaust Heat Shield Bolts
(not shown).
13. Remove Exhaust Heat Shield (5).
Figure 1.
14. Remove Exhaust Manifold Bolt (6) and
seven (7) Nuts (7). Figure 2
15. Remove Exhaust Manifold (1) and
Exhaust Manifold Gasket (8). Discard
gasket.

1

5

4

3
2

Figure 1:
Y-Pipe Assembly (3), Y-Pipe Gasket (4),
Exhaust Manifold Heat Shield (5),
Exhaust Manifold (1), and Nut (2)

8

6

1

7

Figure 2:
Exhaust Manifold (1), Exhaust Manifold
Gasket (8), Exhaust Manifold Nuts (7)
and Bolt (6)

11
12

10

10

13
12
Figure 3:
Exhaust Manifold Visual Inspection Locations

DSM.0052 Ver. 1.0 05/27/2022

488LPI Propane Autogas Engine Mechanical
and Fuel Components Service Manual

Page 52 of 117

INSPECTION PROCEDURE
Visual Inspection Procedure
Inspect Exhaust Manifold for the following
conditions at locations indicated on Figure
3:





Damaged gasket surfaces (10)
Damage to threaded bolt holes (11)
Cracks inside exhaust ports (12)
External cracks (13)

INSTALLATION PROCEDURE
1. Install new Exhaust Manifold Gasket
(8). Figure 4
2. Install Exhaust Manifold (1). Figure 1
3. Install Exhaust Manifold Bolt (6) and
Nuts (7). Figure 2. Refer to Engine
Mechanical Torque and Clearance
Specifications.
4. Install Exhaust Manifold Head Shield
(5) using two (2) Bolts (9). Figure 4.
Refer to Engine Mechanical Torque
and Clearance Specifications.
5. Install Spark Plugs. Refer to Engine
Electrical Sensors and Components
Torque Specifications.
6. Install Spark Plug Wires.
7. Raise vehicle on hoist.
8. Install new Y-Pipe Gaskets. Figure 1
9. Tighten Y-Pipe Hanger (not shown).
Follow OEM procedure.
10. Install Y-Pipe Assembly (3). Figure 1
11. Lower vehicle.
12. Start vehicle, warm up to operating
temperature and check exhaust
manifold flange gaskets for exhaust
leaks.

8
1
5

9
Figure 4:
Exhaust Manifold (1), Exhaust Manifold
Gasket (8), Heat Shield (5), and
Heat Shield Bolts (9)

If exhaust leaks are found, these
must be repaired as exhaust leaks
affect O2 operation.

DSM.0052 Ver. 1.0 05/27/2022

488LPI Propane Autogas Engine Mechanical
and Fuel Components Service Manual

Page 53 of 117

Flexplate and Transmission Adaptor
Replacement
REMOVAL PROCEDURE
1. Secure vehicle on approved hoist.
2. Raise vehicle.
3. Remove Transmission. Follow OEM
procedure.
4. Remove Flexplate Pilot Bolt from
location (1) and six (6) Flexplate
Retaining Bolts (2). Figures 1 and 3
5. Remove Flexplate (3).
6. If replacing Transmission Adaptor (4):
a. Remove six (6) Transmission
Adaptor Retaining Bolts (5). Figure 2
b. Remove Transmission Adaptor (4).

1
4

3

7

6
2

Figure 1:
Flexplate (2) to Crankshaft flange (5) Installation.

5
4
Figure 2:
Transmission Adaptor (4) and Transmission
Adaptor Retaining Bolt Locations (5)

DSM.0052 Ver. 1.0 05/27/2022

488LPI Propane Autogas Engine Mechanical
and Fuel Components Service Manual

Page 54 of 117

INSTALLATION PROCEDURE
1. If removed: Install Transmission
Adaptor (4). Figure 2
2. Install six (6) Transmission Adaptor
Retaining Bolts at locations (5). Figure
2. Refer to Engine Mechanical Torque
and Clearance Specifications.
3. Install Flexplate.
Verify Flexplate mounting holes
(6) line up with corresponding
Crankshaft flange (7) holes and
Flexplate is keyed to
Crankshaft.
4. Finger tighten Pilot Flexplate Bolt (1).
Figure 3

5.

6.
7.
8.
9.

If not pre-applied: Apply Loctite® Blue
to Flexplate Retaining Bolt threads.
Install remaining six (6) Flexplate
Retaining Bolts and tighten in star
pattern shown in Figure 3. Refer to
Engine Mechanical Torque and
Clearance Specifications.
Tighten Flexplate Pilot Bolt (1). Figure
3. Refer to Engine Mechanical Torque
and Clearance Specifications.
Install Transmission. Follow OEM
procedure.
Lower vehicle
Verify proper operation.

DSM.0052 Ver. 1.0 05/27/2022

1
6

3

4

5

1