Jeep Cherokee 4.0 Engine for Sale | OEM Used AMC Inline-6 4.0L “Immortal Six”
$1,999.00
At a Glance
- Condition: OEM used, compression tested across all 6 cylinders
- Availability: In stock, multiple year ranges available 1991 to 2006
- Shipping: Free shipping to all 50 states via freight pallet, 5 to 10 business days
- All 6 cylinders compression tested, results available before you pay
- Year and variant documented (Renix vs HO vs Chrysler era) before shipping
- Cylinder head crack inspection (known 0331 casting concern)
- Donor application documented (Cherokee XJ, Wrangler YJ TJ, Grand Cherokee ZJ WJ, Comanche)
- 100% fitment verified before every order ships
- No core charge required
- Backed by a 15 day replacement warranty against internal defects
Description
About the Jeep Cherokee 4.0 Engine
The Jeep Cherokee uses an AMC I6 engine, one of the most recognizable and longest-running engines in the history of American Motors Corporation (AMC). This Jeep 4.0 engine for sale is from the family of engines kept in production when Chrysler bought AMC in 1987. The engine is even referred to as the “Immortal Six” because of its legendary longevity and rebuildability. Properly maintained, the 4.0 Inline-6 routinely logs 300,000-plus miles between major rebuilds, putting it in the same elite reliability tier as the Toyota 22RE and the Ford 300 Inline-6.
Applications of the Jeep Cherokee 4.0 Engine
- Jeep Cherokee XJ: The 4.0 was a staple in the Cherokee XJ from 1987 to 2001. Available in both Renix-injection (1987 to 1990) and HO (High Output, 1991 onward) variants. The XJ-with-4.0 is one of the most-loved off-road platforms ever produced.
- Jeep Grand Cherokee ZJ and WJ: Used in the Grand Cherokee from 1993 to 2004 as the standard inline-6 option, paired with various automatic and manual transmissions.
- Jeep Wrangler YJ and TJ: Found in the Wrangler from 1991 to 2006. The TJ Wrangler with 4.0 became a defining off-road vehicle of its era.
- Jeep Comanche MJ: Available from 1987 to 1992, the Comanche pickup paired the XJ chassis with a truck bed for compact-truck off-road duty.
- Jeep Wagoneer XJ: Used in the XJ Wagoneer from 1987 to 1990 (the XJ-based Wagoneer, not the full-size SJ Grand Wagoneer).
- Off-Roading: The 4.0 is widely used in custom off-road builds because of its torque and ability to withstand punishment. The engine cast iron block, simple OHV architecture, and low parts cost make it the ideal foundation for serious wheeling builds.
- Rock Crawling: The Jeep 4.0 has low-end torque ideally suited for rock crawling. Combined with TJ / XJ chassis solid axles and proven 4WD systems, the 4.0 is the signature rock-crawler engine.
- Marine Applications: Some marine adaptations use the 4.0 because of its sturdy nature and high torque availability.
- Industrial Equipment: The 4.0 has been used in generators and pumps where reliability matters more than peak power.
- Hot Rods and Custom Cars: Some enthusiasts use the 4.0 in hot rods and custom builds for its torque-rich character and easy availability.
- Engine Swaps: The 4.0 compact dimensions, robust torque, and simple electronics make it a popular swap target into Jeep CJ, classic Land Rover, and various restoration projects.
- Military and Specialty Vehicles: Some military vehicles and specialty off-road vehicles have relied on Jeep 4.0 engines due to the toughness associated with it in tough environments.
Variant Identification, Renix vs HO
This is the most important specification consideration when buying a Jeep 4.0:
| Option | Description |
|---|---|
| Renix Era (1987 to 1990) | First-generation 4.0L. Renault Bendix (Renix) fuel injection system, 173 hp, distributor ignition. Less desirable for swaps due to harder-to-find Renix parts. |
| HO (High Output) Era (1991 to 1995) | Chrysler-developed update. New cylinder head, revised intake, new fuel injection (Chrysler MPFI), 190 hp. The most desirable swap target. |
| OBD-II Era (1996 to 2001) | Chrysler-controlled era. Continued 190 hp output with OBD-II diagnostics. Still excellent reliability. |
| TJ Final Years (2002 to 2006) | Final 4.0 production. 190 to 195 hp. Updated electronics. The last factory-installed AMC straight-six. |
Key Features of the Jeep Cherokee 4.0 Engine
- Engine Design and Configuration: The 4.0L engine uses an inline-six cylinder format, an arrangement that delivers smooth operation and balanced power output. With a displacement of 4.0 liters (242 cubic inches), this engine uses an OHV (Overhead Valve) cam-in-block pushrod design. As a result of this configuration, the engine is simpler and more rebuildable than overhead camshaft designs, and the 4.0 is famously easy to maintain and repair compared to many modern V6 engines.
- Performance Attributes: The 4.0 makes between 173 and 195 horsepower depending on year and variant. Torque ranges from 220 to 235 lb-ft, suitable for off-roading and towing due to strong low-end and mid-range delivery. The engine pulls hard from idle, exactly the character needed for rock crawling and trail driving.
- Durability and Reliability: The defining feature of the engine. Cast iron block AND cast iron cylinder head construction makes the 4.0 extraordinarily durable. It can comfortably exceed 300,000 miles when properly maintained. Cooling is effective when the system is well-maintained, important for off-road operation in difficult terrain.
- Ease of Maintenance: The OHV design lacks the complex features of modern overhead-cam engines and is therefore far easier to repair. Parts for the 4.0 are widely available and relatively inexpensive due to the long production run and widespread use of this engine across multiple Jeep models. This availability makes repair and maintenance accessible to all Jeep owners.
- Off-Road Capability: The 4.0 strong low-end torque is ideal for off-road use. Climbing and crawling require adequate low-end power, and the 4.0 delivers it abundantly. Combined with strong 4WD systems in Jeep vehicles, the 4.0 is critical to the off-road performance of the Cherokee XJ, Wrangler YJ / TJ, Grand Cherokee, and Comanche MJ.
- MPFI Fuel Injection: Multi-point fuel injection (MPFI) starting in 1987 provided cleaner cold starts, better throttle response, and improved fuel economy compared to the carbureted predecessors.
Signs You Need a Replacement 4.0
- Loss of compression on one or more cylinders
- Cylinder head cracks (the 0331 casting used 2000 to 2001 is documented as crack-prone, particularly between cylinders 3 and 4)
- Excessive oil consumption past piston rings
- Connecting rod or main bearing knock under load
- Excessive blowby through the PCV system
- Donor Cherokee XJ, Wrangler, or Grand Cherokee has been totaled and the engine is being moved
- High-mileage Wrangler TJ owner planning a long-term keeper build
- XJ restoration project requiring fresh starting block
- Off-road / rock crawler build wanting a known-good base
Known Jeep 4.0 Issues We Inspect Before Shipping
- 0331 cylinder head cracks (2000-2001 castings): A documented Jeep 4.0 weakness. The 0331 cylinder head casting used on 2000 and 2001 model year engines is prone to cracking between cylinders 3 and 4. We pressure test or visually inspect heads, particularly on 2000-2001 era cores. Earlier 7120 and 0630 heads are more reliable.
- Cracked exhaust manifold: A known issue particularly on TJ Wranglers, often visible from underneath. Documented before shipping.
- Rear main seal leak: Common at high mileage. Inspected and disclosed.
- Renix vs HO confusion: We confirm variant before shipping based on year, intake manifold style, and ECU connector type.
- Connecting rod bearing wear: Listened for during run test.
- Cooling system condition: Inspected; a healthy cooling system is critical to 4.0 longevity.
What Ships and What Does Not
| Item | Details |
|---|---|
| INCLUDED | Long block: cast iron block, crank, rods, pistons, camshaft and lifters, cast iron cylinder head, valve train, oil pan, valve cover, intake manifold (typical), exhaust manifold (typical). |
| NOT INCLUDED | ECU and harness (sold separately, application-specific), throttle body, alternator, starter, A/C compressor, power steering pump, water pump (typical), thermostat, flexplate (auto) or flywheel (manual), motor mounts, distributor (Renix variants). |
| Fluids | Drained before shipping. Refill with 10W-30 motor oil. Regular unleaded 87 octane fuel acceptable. |
| Core Note | No core charge. You are not required to return your old engine. |
Jeep 4.0 Myth Busters
- Myth: All Jeep 4.0 engines have overheating issues.
- Reality: Overheating is typically a result of neglected cooling systems, undersized radiators, clogged passages, or aged thermostats. Upgrading components like the radiator, fan clutch, and thermostat effectively prevents overheating issues. The 4.0 itself is not inherently prone to overheating with proper cooling system maintenance.
- Myth: The Jeep 4.0 engine is fuel-inefficient.
- Reality: While not as efficient as modern engines with direct injection and 8-speed transmissions, the Jeep 4.0 offers respectable fuel economy for its class, particularly considering its torque and capabilities. XJ Cherokee with 4.0 typically delivers 16 to 19 mpg city / 20 to 23 mpg highway depending on transmission and conditions.
- Myth: The Jeep 4.0 lacks power.
- Reality: While not the most powerful engine of its era, the Jeep 4.0 torque-rich performance (220 to 235 lb-ft) makes it well-suited for off-road driving and towing. The torque-to-weight ratio of an XJ or TJ with 4.0 is excellent for trail use.
- Myth: All Jeep 4.0 engines suffer from cracked cylinder heads.
- Reality: Only the 0331 casting used on 2000 and 2001 model year engines is documented as crack-prone. Earlier heads (7120, 0630) and later heads are reliable. Replacement options and improved aftermarket heads (TUPY 0630, Mopar updated castings) mitigate this issue.
- Myth: The Jeep 4.0 is difficult to work on.
- Reality: The Jeep 4.0 popularity means there is ample documentation, community support, parts availability, and aftermarket development, making it relatively easy to work on for enthusiasts and mechanics. The XJ and TJ communities have decades of accumulated knowledge.
Vehicle Compatibility
The Jeep 4.0 fits the following vehicles directly:
| Vehicle | Compatibility |
|---|---|
| Jeep Cherokee XJ | 1987 to 2001 (Renix 1987 to 1990, HO 1991 to 2001) |
| Jeep Wrangler YJ | 1991 to 1995 (HO 4.0 introduction in YJ) |
| Jeep Wrangler TJ | 1997 to 2006 (HO 4.0 throughout TJ run) |
| Jeep Grand Cherokee ZJ | 1993 to 1998 (4.0 base inline-6 option) |
| Jeep Grand Cherokee WJ | 1999 to 2004 (4.0 base inline-6 option) |
| Jeep Comanche MJ | 1987 to 1992 |
| Jeep Wagoneer XJ | 1987 to 1990 |
Variant differences (Renix vs HO) require matching ECU and harness. Confirm year and variant before ordering.
Inspection Workflow
Every used Jeep 4.0 we ship goes through this process:
- Compression test across all 6 cylinders, pressure per cylinder recorded
- Cylinder head crack inspection (0331 casting concern on 2000-2001 cores)
- Variant authenticated (Renix vs HO vs Chrysler era) by year, intake style, and head casting code
- Cylinder head casting code documented (7120, 0630, 0331, etc.)
- Donor application photographed and documented (XJ, TJ, ZJ, WJ, MJ)
- Exhaust manifold crack inspection (TJ-era concern)
- Rear main seal condition assessed
- Approximate mileage documented when verifiable
Where mileage is verified, it is shared. Where mileage cannot be confirmed, we disclose openly before payment.
Why Buy From Part Nests
- All 6 cylinders compression tested, results before you pay
- Cylinder head crack inspection (0331 casting concern checked)
- Variant authenticated (Renix vs HO) for ECU and harness matching
- Head casting code documented (7120, 0630, 0331, later)
- Donor application documented (Cherokee XJ, Wrangler YJ TJ, Grand Cherokee ZJ WJ, Comanche)
- Free freight pallet to all 50 states, no hidden fees
- No core charge, keep your old engine
- 15 day replacement warranty on internal defects
- Call (240) 306-7051 to confirm Jeep year, variant (Renix vs HO vs Chrysler era), and head casting code before ordering
15 Day Replacement Warranty
Every used Jeep 4.0 engine purchased through Part Nests carries a 15 day replacement warranty starting on the delivery date.
What Is Covered
- Internal defects already present when the engine arrives
- Compression failures on any of the 6 cylinders beyond what was disclosed
- Cylinder head crack failures within 15 days from installation (where head was documented as crack-free at shipping; 0331 castings inspected with extra care)
- Connecting rod, lifter, or bearing failures within 15 days from installation
- Excessive oil consumption beyond what was disclosed
- Incorrect variant shipped (Renix vs HO vs Chrysler era) due to an error on our end
What Is Not Covered
- Damage caused during installation
- Damage from operating with neglected cooling system (the 4.0 is sensitive to cooling system condition; replace thermostat and water pump at install if condition unknown)
- Damage from running with incorrect ECU calibration (Renix and HO require different ECUs and harnesses; cross-installation requires the matching electrical system)
- Damage from extended oil change intervals or incorrect oil viscosity (Jeep-spec 10W-30 recommended)
- Damage from cracked exhaust manifold (a separate component, inspected and disclosed at shipping but not covered for replacement)
- External components (ECU, harness, throttle body, alternator, starter, A/C, P/S, water pump, thermostat, flexplate or flywheel, motor mounts, distributor on Renix variants) unless itemized
- Labor expenses of any kind
To start a warranty claim, reach us within 15 days of delivery at (855) 634-4447.
- All 6 Cylinders Tested: Compression results documented before payment
- Cylinder Head Crack Inspection: 0331 casting concern checked, casting code documented
- Variant Authenticated: Renix (1987-1990) vs HO (1991-plus) vs Chrysler era confirmed
- Donor Application Documented: XJ, TJ, ZJ, WJ, MJ source identified
- Exhaust Manifold Inspected: TJ-era crack concern assessed
- 15 Day Replacement Cover: Internal defects protected from delivery onward
Additional information
| aspiration | Naturally Aspirated |
|---|---|
| camshaft-type | OHC |
| compression-ratio | 8.8:1 to 9.2:1 |
| configuration | Inline-6 (I6) |
| cylinder-block-alloy | Cast Iron |
| cylinder-bore | 3.88 in |
| fuel-system | Multi-Point Fuel Injection |
Two distinct fuel injection and electrical eras. The Renix era (1987 to 1990) used the Renault Bendix (Renix) fuel injection system, distributor ignition, and produced 173 hp. The HO (High Output) era began in 1991 with a Chrysler-developed update: new cylinder head, revised intake manifold, Chrysler MPFI fuel injection, and 190 hp output. The HO is significantly more desirable for swaps and replacements because Renix parts are harder to find, the Renix ECU and harness are more limited, and the HO is the more refined design. We confirm variant by year, intake manifold style, and ECU connector type before shipping.
Cylinder head cracking on 2000-2001 castings. The 0331 cylinder head casting used on 2000 and 2001 model year Jeep 4.0 engines is documented as crack-prone, particularly between cylinders 3 and 4. The crack typically develops after sustained heat cycling. Earlier head castings (7120 used through the 1990s, 0630 used in late HO era) and later castings are not prone to this issue. We inspect every Jeep 4.0 cylinder head for casting code and crack evidence before shipping. If the casting is 0331 from a 2000-2001 donor, we apply extra scrutiny and disclose openly. Many builders proactively replace 0331 heads with the more reliable 7120 or 0630 castings, or with aftermarket Mopar updated castings.
Cherokee XJ, Grand Cherokee ZJ and WJ, Wrangler YJ and TJ, Comanche MJ, and XJ Wagoneer. The 4.0 was the staple AMC/Chrysler inline-6 in compact and mid-size Jeeps from 1987 to 2006. The XJ Cherokee (1987 to 2001) is the longest-running application. The TJ Wrangler (1997 to 2006) is the most-loved off-road application. The Grand Cherokee ZJ (1993 to 1998) and WJ (1999 to 2004) used the 4.0 as the base inline-6 option. The Comanche MJ (1987 to 1992) pickup used the 4.0. Some variants are direct cross-fit; others require minor changes to oil pan, intake routing, or ECU.
Mechanically yes, but the electrical systems differ. The Renix and HO 4.0 share the same fundamental block, head architecture, and rotating assembly. However the Renix uses Renault Bendix fuel injection, a distributor, and a Renix ECU and harness; the HO uses Chrysler MPFI, distributorless or distributor ignition (varying by year), and a Chrysler ECU and harness. Cross-installation requires the matching electrical system from the donor chassis. For an HO chassis, source an HO engine. For a Renix chassis, source a Renix engine. We confirm variant on every order to match your application correctly.
Common on TJ Wrangler 4.0 engines. The TJ-era 4.0 exhaust manifold is prone to cracking, typically at the cylinder 3 and 4 runners, due to expansion and contraction cycles. The crack is visible from underneath the truck and produces an exhaust leak. Replacement manifolds (OEM Mopar, aftermarket Dorman, Doug Thorley headers) are readily available. We inspect for cracked exhaust manifold before shipping and disclose openly. The manifold itself is not covered under engine warranty (it's a separate component) but we make sure buyers know what they're getting.
Yes, a popular conversion. Swapping the 4.0 into a CJ-5, CJ-7, or CJ-8 is one of the most common Jeep engine swaps. The 4.0 produces significantly more power and torque than the original AMC 258 (4.2L straight-six) that came in the CJ. The swap requires CJ-to-4.0 motor mounts, modified driveshaft, modified fuel system (the CJ originally had a carbureted system; the 4.0 needs MPFI fuel delivery), modified exhaust, and the matching Chrysler ECU and harness. Specialty CJ-to-4.0 swap kits are available from multiple suppliers.
300,000-plus miles with proper maintenance. The Jeep 4.0 earned the nickname "Immortal Six" because of its legendary longevity. Cast iron block, cast iron cylinder head, OHV pushrod design, simple electronics, and conservative power output combine to give the 4.0 exceptional durability. XJ Cherokees with the 4.0 routinely log 300,000-plus miles on the original short block when maintained on regular oil changes, cooling system service, and timely repair of small issues. The engine is also extremely rebuildable; rebuild kits are widely available and affordable.
No. There is no core return required.
2 reviews for Jeep Cherokee 4.0 Engine for Sale | OEM Used AMC Inline-6 4.0L “Immortal Six”
Related products
Recently Viewed Products
Tyler R. –
Got an HO 4.0 from a 1997 Cherokee XJ donor for a 1996 XJ repower. HO variant correctly identified (Chrysler MPFI, distributor ignition), 7120 head casting documented (not the problematic 0331). All 6 cylinders compression tested. Honest pre-purchase information about the 0331 vs 7120 head casting distinction. XJ trail-ready again.
Marissa J. –
Sourced a 4.0 for a 2002 Wrangler TJ replacement. Chrysler era variant (post-OBD-II) correctly identified, head casting code documented, exhaust manifold inspection found a minor crack (disclosed openly with replacement manifold sourcing guidance). Foundation for the TJ keeper build with the legendary Immortal Six.