2.5l 4-cyl - VIN [e] Jeep Wrangler I

ENGINE IDENTIFICATION

Note. For engine repair procedures not covered in this article, see ENGINE OVERHAUL PROCEDURES - GENERAL INFORMATION article in the GENERAL INFORMATION section.

Engine can be identified by eighth character of Vehicle Identification Number (VIN). The VIN is stamped on a plate attached to top left corner of instrument panel.

ENGINE IDENTIFICATION CODES

SPECIAL ENGINE MARKS

Some engines are produced at the factory with oversize or undersize components. These are identified by a letter code stamped on filter boss near distributor. Letters are decoded as follows

1. "B" indicates all cylinder bores .010" (.25 mm) oversize.
2. "C" indicates all camshaft bearing bores .010" (.25 mm) oversize.
3. "M" indicates all main bearing journals .010" (.25 mm) undersize.
4. "P" indicates all connecting rod journals .010" (.25 mm) undersize.
5. "PM" indicates all crankshaft main bearing journals and one or more connecting rod journals .010" (.25 mm) undersize.

ENGINE

See ENGINE article.

INTAKE MANIFOLD

Removal

1. Disconnect negative battery cable. Remove air inlet hose at throttle body and air cleaner. Remove power steering pump with hoses attached and wire aside.
2. Remove power steering pump brackets at water pump and intake manifold. Disconnect Black fuel supply tube and Gray fuel return tube at throttle body. CAUTION: DO NOT pry cruise control connector. Use finger pressure only. Prying could break connector.
3. Disconnect accelerator cable and cruise control connector at throttle body. Remove PCV hose. Disconnect all electrical connectors and vacuum hoses and mark for installation.
4. Loosen EGR valve tube nut. Remove EGR valve tube-to-exhaust manifold bolts. Drain cooling system. Remove bolts No. 2 through 5 securing intake manifold to cylinder head. (Scheme 1) Loosen bolt No. 1 and nuts 6 and 7. Remove intake manifold.

Scheme 1

Installation

1. Ensure all gasket surfaces are clean. Install intake manifold. Finger tighten all bolts. Torque intake manifold bolts to specification in correct sequence. (Scheme 1)and «TORQUE SPECIFICATIONS»(/jeep/wrangler/i-1986-1995/remont/mechanical/#25l-4-cyl-vin-e) table.
2. Clean oxygen sensor threads. Apply anti-seize on oxygen sensor threads before installation. Install sensor and tighten to specification. To complete installation, reverse removal procedure. Fill and bleed cooling system.

Note. Remove coolant temperature sensor from back of intake manifold when filling system to bleed trapped air.

1. Disconnect negative battery cable. Drain cooling system. Loosen EGR tube nut at intake manifold. Remove EGR tube bolts at exhaust manifold. Remove intake manifold. See «INTAKE MANIFOLD»(/jeep/wrangler/i-1986-1995/remont/mechanical/#25l-4-cyl-vin-e__intake-manifold) under REMOVAL & INSTALLATION.
2. Disconnect all electrical connectors and vacuum hoses and mark for installation. Raise and support vehicle. Disconnect exhaust pipe from exhaust manifold.
3. Remove O2 sensor. Lower vehicle. Remove EGR valve tube from intake and exhaust manifold. Remove exhaust manifold bolts. Remove exhaust manifold.

1. Ensure all gasket surfaces are clean. Install exhaust manifold. Finger tighten all bolts. Torque exhaust manifold bolts to specification in sequence. (Scheme 1)and «TORQUE SPECIFICATIONS»(/jeep/wrangler/i-1986-1995/remont/mechanical/#25l-4-cyl-vin-e) table.
2. Clean O2 sensor threads. Apply anti-seize on oxygen sensor threads before installation. Install sensor and tighten to specification. To install remaining components, reverse removal procedures. Fill cooling system. Remove coolant temperature sensor switch, located in inlet manifold, to bleed air from system while filling.

1. Disconnect negative battery cable. Drain cooling system. Remove air cleaner. Remove A/C compressor (if equipped). Wire compressor out of working area. DO NOT discharge A/C system.
2. Remove A/C mounting bracket-to-cylinder head bolts. Loosen A/C mounting bracket-to-cylinder block bolts. Disconnect upper radiator hose and heater hoses. Remove valve cover.
3. Remove rocker arms and push rods. See «ROCKER ARMS & BRIDGE»(/jeep/wrangler/i-1986-1995/remont/mechanical/#25l-4-cyl-vin-e) under VALVES. Remove intake and exhaust manifolds as previously described. 4) Disconnect and mark spark plug wires. Remove spark plugs. Remove cylinder head bolts. Remove cylinder head.

Inspection

Inspect cylinder head for cracks or damage. Using straightedge, check cylinder head for warpage in several areas. Repair or replace cylinder head if warpage exceeds specification or damage exists. See ENGINE SPECIFICATIONS tables.

1. Ensure all gasket surfaces are clean. Clean carbon from combustion chambers and tops of pistons. Install new cylinder head gasket with numbers or word "TOP" upward. Ensure all holes align.
2. Install cylinder head. Apply sealing compound to cylinder head bolt No. 7 threads before installation. (Scheme 2) Install head bolts.
3. Torque all bolts in sequence and to specification. (Scheme 2) See «TORQUE SPECIFICATIONS»(/jeep/wrangler/i-1986-1995/remont/mechanical/#25l-4-cyl-vin-e__torque-specifications) table. To install remaining components, reverse removal procedures. Fill cooling system. Remove coolant temperature sensor from intake manifold to bleed air from system while filling.

Scheme 2

Valve Arrangement

E-I-I-E-E-I-I-E (Front-to-rear).

Removal & Installation

1. Remove PCV valve hose at valve cover. Remove valve cover. Alternately loosen each rocker arm bolt one turn at a time to avoid damaging bridges.
2. Remove bridges, pivots and corresponding pairs of rocker arms. Remove push rods. Mark all components for reassembly. Components must be installed in original location. To install, reverse removal procedure.
3. Install rocker arm components in original location. Torque bolts to specification. See «TORQUE SPECIFICATIONS»(/jeep/wrangler/i-1986-1995/remont/mechanical/#25l-4-cyl-vin-e__torque-specifications) table.

Valve Guides

Valve guides are not replaceable. If clearance is excessive, valve guides must be reamed for oversized stem valves.

1. Remove valve cover. Remove rocker arms and push rods. See «ROCKER ARMS & BRIDGE»(/jeep/wrangler/i-1986-1995/remont/mechanical/#25l-4-cyl-vin-e) under VALVES. Using Lifter Remover/Installer (7625), remove lifter through push rod openings of cylinder head.
2. Mark lifter location for reassembly reference. Lifters must be installed in original location. Inspect lifters and camshaft mating surfaces for wear and replace if wear is found. NOTE: Before installing lifters, soak in Jeep/Eagle Super Oil Conditioner or equivalent.
3. To install, reverse removal procedures. Install lifter in original location. Torque all bolts to specification. See «TORQUE SPECIFICATIONS»(/jeep/wrangler/i-1986-1995/remont/mechanical/#25l-4-cyl-vin-e__torque-specifications) table.

Note. Pour remainder of Jeep/Eagle Super Oil Conditioner, or equivalent, over entire valve train assembly. Leave conditioner with engine oil for at least 1000 miles or until next scheduled oil change.

1. Disconnect negative battery cable. Remove drive belts, fan and hub assembly. Remove fan shroud. Remove accessory drive brackets attached to timing case cover.
2. Remove A/C compressor (if equipped) with hoses attached and wire aside. DO NOT discharge A/C system. Remove alternator bracket assembly from cylinder head.
3. Remove vibration damper retaining bolt and washer. Remove vibration damper and key. Remove oil pan-to-front cover bolts. Remove cover-to-block retaining bolts. Remove engine front cover.
4. Cut oil pan gasket even with face of cylinder block. Remove gasket from oil pan. Remove crankshaft oil seal from cover.

1. Ensure all gasket surfaces are clean. Ensure oil slinger is installed on crankshaft. Apply sealing compound on both sides of front cover gasket. Install gasket on cylinder block. Replace front section of oil pan seal with similar section fabricated from new seal.
2. Coat seal with RTV sealant and place in position. Apply sealant where oil pan and cylinder block meet. Place front cover on cylinder block. Place Front Cover Alignment/Seal Installer (6139) in front engine cover seal area.
3. Install cover retaining bolts and tighten to specification. See «TORQUE SPECIFICATIONS»(/jeep/wrangler/i-1986-1995/remont/mechanical/#25l-4-cyl-vin-e__torque-specifications) .
4. Apply sealant to front cover seal outer diameter and lightly coat crankshaft with oil. Place front cover seal installer on front of crankshaft. Tap seal into front cover. Remove seal installer. Lightly coat seal contact area of vibration damper with oil and place on crankshaft.
5. To complete installation, reverse removal procedures. Lubricate vibration damper retaining bolt with oil before installation. Torque bolts to specification.

Removal & Installation (Front Cover Removed)

1. Pry oil seal from front cover. Install replacement seal with open end of seal toward inside of cover. Apply sealant to seal outer diameter.
2. Support engine front cover at seal area while installing front cover seal and install it into position with Front Cover Alignment/Seal Installer (6139).

Removal & Installation (Front Cover Installed)

1. Remove drive belts. Remove vibration damper. Remove radiator shroud. Remove seal from front cover. Position new seal on front cover Alignment/Seal Installer (6139) with lip facing outward.
2. Apply sealant to seal outer diameter. Lightly coat crankshaft with oil. Place Front Cover Alignment/Seal Installer (6139) on front of crankshaft. Tap seal into front cover. Remove seal installer. Lightly coat seal contact area of vibration damper with oil.
3. Install key in crankshaft (if removed). Install vibration damper. Lubricate vibration damper bolt with oil. Install retaining bolt and washer. Torque to specification. See «TORQUE SPECIFICATIONS»(/jeep/wrangler/i-1986-1995/remont/mechanical/#25l-4-cyl-vin-e__torque-specifications) table.

1. Disconnect negative battery cable. Drain cooling system. Remove radiator. Discharge A/C system (if equipped). Remove A/C condenser. Remove engine front cover. See ENGINE FRONT COVER under CAMSHAFT.
2. Remove distributor. Remove valve cover. Remove rocker arms and push rods. See «ROCKER ARMS & BRIDGE»(/jeep/wrangler/i-1986-1995/remont/mechanical/#25l-4-cyl-vin-e) under VALVES.
3. Remove valve lifters. Mark lifters for reinstallation reference. Remove crankshaft oil slinger. Pull chain tensioner block toward tensioner lever to compress spring. Hold block and move tensioner lever to lock position. (Scheme 3)
4. Rotate crankshaft and align timing marks on crankshaft and camshaft gears. Remove camshaft gear retaining bolt. Remove gears and timing chain. Remove camshaft.

Scheme 3

Inspect camshaft for flaking, lobe height wear or worn bearing journals. Replace if not within specification. See ENGINE SPECIFICATIONS tables. If camshaft gear or chain rubs against engine front cover, examine oil pressure relief holes in rear camshaft journal and ensure they are free of debris.

1. Lubricate camshaft and install. Avoid damage to camshaft bearings. Install timing gears and timing chain. Rotate crankshaft and camshaft so timing marks align. (Scheme 4)
2. Install camshaft gear retaining bolt. Torque to specification. See «TORQUE SPECIFICATIONS»(/jeep/wrangler/i-1986-1995/remont/mechanical/#25l-4-cyl-vin-e__torque-specifications) table. Install crankshaft oil slinger. Position chain tension tensioner lever to the unlock (down) position. (Scheme 3) To complete installation, reverse removal procedure.

Scheme 4

Information not available from manufacturer. DO NOT replace camshaft bearings unless special removal and installation tools are available.

OIL PAN

See OIL PAN REMOVAL at end of ENGINE section.

1. Remove cylinder head. See «CYLINDER HEAD»(/jeep/wrangler/i-1986-1995/remont/mechanical/#25l-4-cyl-vin-e) under MANIFOLDS & CYLINDER HEAD. Remove oil pan. See OIL PAN REMOVAL article. Remove ridge or deposits from cylinder bore.
2. Mark connecting rod and piston for cylinder identification. Remove bearing cap. Remove piston and rod assembly.

Scheme 5

1. Ensure ring end gap and side clearance are within specification. See ENGINE SPECIFICATIONS tables. Install rings on piston. Position ring end gaps at specified area. Ring gaps may vary 20 degrees from positions illustrated. (Scheme 5)
2. Lubricate piston assembly and cylinder block. Install piston assembly. Arrow on top of piston must face toward front of engine and connecting rod oil squirt hole should face camshaft when installed.
3. Install rod bearings. Check oil clearance and connecting rod side play clearance. To install remaining components, reverse removal procedures. Torque bolts to specification. See «TORQUE SPECIFICATIONS»(/jeep/wrangler/i-1986-1995/remont/mechanical/#25l-4-cyl-vin-e__torque-specifications) table.

Fitting Pistons

1. Determine piston clearance. For piston clearance specification, see ENGINE SPECIFICATIONS tables. Pistons up to .004" (.10 mm) undersize may be enlarged by knurling or shot-peening. If clearance is not within specification, install new pistons.
2. Measure inside diameter of cylinder bore at 2.31" (58.73 mm) below top of bore. Measure outside diameter of piston. Measure piston at right angle of piston pin at the center line of the pin. Compare reading to diameter of cylinder bore to determine piston clearance.

Position piston on support, pin pilot and driver on an arbor press. (Scheme 6) Press piston pin from piston. Discard pin.

Note. Piston and pin must be at room temperature when measuring fit. Piston pin should fall through the piston at room temperature. If pin jams in pin bore, replace piston. Piston pin cannot be reused after removal.

Inspect piston pin bore in connecting rod for nicks and burrs. Remove nicks and burrs as required. With pin removed from piston and connecting rod, clean piston pin bore and replacement piston pin.

Note. Position connecting rod on piston so oil squirt hole faces camshaft side of the engine and arrow on piston points to front of engine.

Scheme 6

1. Insert pin pilot through piston and connecting rod. Ensure arrow on piston crown is pointing up. Place assembly on support with squirt hole of connecting rod to left side. Insert piston pin through the upper piston pin bore and into connecting rod pin bore. (Scheme 6)
2. Position driver inside pin. Using arbor press, press pin through rod and piston bores until pilot indexes with mark on support. Remove piston and connecting rod. Pin should be centered in rod.
3. Piston pin installation requires a 2000 lb. (907 kg) press fit. Replace connecting rod if noticeably less effort is encountered.

CONNECTING ROD BEARINGS

Note. In production, crankshaft journal diameters are indicated by a color coded mark placed on the flanged (rear) end of crankshaft or adjacent counterweight. Color code determines bearing usage, if old bearings are reused. Check oil clearance with Plastigage after bearing installation.

1. Remove oil pan. See OIL PAN REMOVAL & INSTALLATION article in ENGINES. Remove oil pump. See «OIL PUMP»(/jeep/wrangler/i-1986-1995/remont/mechanical/#25l-4-cyl-vin-e) under ENGINE OILING.
2. Rotate crankshaft to position rod to be serviced at bottom of stroke. Mark bearing cap and connecting rod. Remove bearing cap with bearing. Push piston and rod assembly up to remove upper bearing.

1. Note color code on edge of bearings removed. Install bearings. Using Plastigage method, check bearing clearances. Replace bearings as necessary to obtain correct clearance. See ENGINE SPECIFICATIONS tables. Bearings are available for standard and undersize application.
2. If required, different sized upper and lower bearings may be installed to obtain correct oil clearance. Torque bolts to specification. Check rod side play. Rotate crankshaft to ensure freedom of movement. To install remaining components, reverse removal procedures. Torque bolts to specification. See «TORQUE SPECIFICATIONS»(/jeep/wrangler/i-1986-1995/remont/mechanical/#25l-4-cyl-vin-e__torque-specifications) table.

Note. Avoid combining bearing inserts in excess of .001" (.02 mm) difference in size. Odd size inserts must be on bottom (rod cap) side.

1. Remove oil pan. See OIL PAN REMOVAL article. Remove oil pump. See «OIL PUMP»(/jeep/wrangler/i-1986-1995/remont/mechanical/#25l-4-cyl-vin-e) under ENGINE OILING.
2. Before removal, ensure main bearing caps are marked for location. Rotate crankshaft to remove bearings. Note color code on edge of bearing.

Note. In production, crankshaft journal diameters are indicated by a color-coded mark placed on flanged (rear) end of crankshaft or adjacent counterweight. Color code determines bearing usage if old bearings are reused. Check oil clearance with Plastigage after bearing installation.

1. Note color code on edge of bearings removed. Install bearings. Ensure caps are installed in original location. Use Plastigage method to check bearing clearances.
2. Replace bearings as necessary to obtain correct clearance. Bearings are available in standard and undersize applications. If required, different sized upper and lower bearings may be installed to obtain correct oil clearance. NOTE: If different sized bearings are used, the odd sized bearings must all be uniform in location (upper or lower). DO NOT use bearings with a thickness difference exceeding .001" (.02 mm).
3. Apply Loctite to corners of rear main bearing cap before final installation. Torque bolts to specification. Check crankshaft end play. Rotate crankshaft to ensure freedom of movement. To install remaining components, reverse removal procedures. Torque bolts to specification. See «TORQUE SPECIFICATIONS»(/jeep/wrangler/i-1986-1995/remont/mechanical/#25l-4-cyl-vin-e__torque-specifications) .

Remove transmission, clutch housing and flywheel or drive plate. Using screwdriver, pry oil seal from housing. Avoid damage to surrounding area.

Coat outer lip of replacement rear main bearing seal with engine oil. Using Seal Installer (6271), install rear main bearing seal flush with cylinder block. To complete installation, reverse removal procedure. Torque all bolts to specification. See TORQUE SPECIFICATIONS table.

WATER PUMP

1. Disconnect negative battery cable. Drain cooling system. Remove fan shroud and drive belts. Remove fan assembly.
2. Disconnect heater hoses and lower radiator hose at water pump. Remove water pump retaining bolts. Remove water pump.

Clean all gasket surfaces. Install water pump. Torque bolts to specification. See TORQUE SPECIFICATIONS table. Ensure pump turns freely. To install remaining components, reverse removal procedures. Fill and purge air from cooling system.

Note. Remove coolant temperature sensor switch from intake manifold to bleed air from system while filling.

CRANKCASE CAPACITY

Crankcase capacity is 4 qts. (3.8L) with oil filter change.

NORMAL OIL PRESSURE

Normal oil pressure should be 25-35 psi (1.8-2.5 kg/cm 2 ) at 800 RPM or 37-75 psi (2.6-5.3 kg/cm 2 ) at 1600 RPM.

OIL PRESSURE REGULATOR VALVE

Nonadjustable Oil pressure regulator valve is located in oil pump body.

OILING SYSTEM

Engine lubrication is provided by the distributor driven gear-type oil pump. Oil is supplied through the full-flow oil filter to an internal oil passage, running along right side of block and intersecting lifter bores. Oil is then routed to camshaft and crankshaft bearings. Oil is supplied to rocker arms from the hydraulic lifters and through the push rods. By-pass valves are located in oil filter mounting and oil pump.

Remove oil pan. See OIL PAN REMOVAL article. Remove oil pump retaining bolts.

Disassembly & Inspection

Disassemble pump. Inspect for wear or damage. Using feeler gauge, measure gear-to-body clearance. Rotate gears and measure each tooth-to-body clearance. Replace oil pump if not within specification. See OIL PUMP SPECIFICATIONS table.

OIL PUMP SPECIFICATIONS

Reassembly & Installation

1. To reassemble, reverse disassembly procedures. Apply Permatex No. 2 to pick-up pipe prior to installation. To install use Pipe Installer (7624). Ensure pick-up pipe support bracket is aligned with pump cover bolt.
2. Fill pump cavity with petroleum jelly before installing pump cover. Apply Loctite on pump cover area. Install cover and bolts. Tighten bolts to specification. Check pump gears for freedom of rotation.
3. Install oil pump and new gasket. Tighten retaining bolts to specification. See «TORQUE SPECIFICATIONS»(/jeep/wrangler/i-1986-1995/remont/mechanical/#25l-4-cyl-vin-e__torque-specifications) .

TORQUE SPECIFICATIONS

TORQUE SPECIFICATIONS

GENERAL ENGINE SPECIFICATIONS

GENERAL ENGINE SPECIFICATIONS

PISTON/PIN/RING SPECIFICATIONS

PISTONS, PINS & RINGS SPECIFICATIONS

BEARING SPECIFICATIONS

CRANKSHAFT MAIN & CONNECTING ROD BEARINGS SPECS

CONNECTING ROD SPECIFICATIONS

CONNECTING ROD SPECIFICATIONS

CYLINDER HEAD SPECIFICATIONS

CYLINDER HEAD SPECIFICATIONS

CYLINDER BLOCK SPECIFICATIONS

CYLINDER BLOCK SPECIFICATIONS

VALVE/VALVE SPRING SPECIFICATIONS

VALVES & VALVE SPRINGS SPECIFICATIONS

VALVE LIFTERS

VALVE LIFTERS SPECIFICATIONS

CAMSHAFT SPECIFICATIONS

CAMSHAFT SPECIFICATIONS

See also:
• ENGINE OVERHAUL PROCEDURES - GENERAL INFORMATION
• TORQUE SPECIFICATIONS
• INTAKE MANIFOLD
• TORQUE SPECIFICATIONS