There are many stories about where the name "jeep" came from. These, although they make for interesting and memorable stories, are not quite accurate.

• Probably the most popular notion has it that the vehicle bore the designation "GP" (for "General Purpose"), which was phonetically slurred into the word jeep. R. Lee Ermey, on his television series Mail Call, disputes this, saying that the vehicle was designed for specific duties, was never referred to as "General Purpose," and that the name may have been derived from Ford's nomenclature referring to the vehicle as GP (G for government-use, and P to designate its 80-inch-wheelbase). "General purpose" does appear in connection with the vehicle in the WW2 TM 9-803 manual, which describes the vehicle as "... a general purpose, personnel, or cargo carrier especially adaptable for reconnaissance or command, and designated as ¼-ton 4x4 Truck", and the vehicle is designated a "GP" in TM 9-2800, Standard Military Motor Vehicles, 1 September 1943, but whether the average jeep-driving GI would have been familiar with either of these manuals, is open to debate.

• Many, including Ermey, claim that the likelier origin refers to the character Eugene the Jeep in the Thimble Theater (Popeye) comic strip. Eugene the Jeep was dog-like and could walk through walls and ceilings, climb trees, fly, and just about go anywhere it wanted; it is thought that soldiers at the time were so impressed with the new vehicle's versatility that they informally named it after the character. The character "Eugene the Jeep" was created in 1936.

• The term "jeep" was first commonly used during World War I (1914-1918) by soldiers as a slang word for new recruits and for new unproven vehicles. This is according to a history of the vehicle for an issue of the U.S. Army magazine, Quartermaster Review, which was written by Maj. E. P. Hogan. He went on to say that the slang word "jeep" had these definitions as late as the start of World War II.

• "Jeep" had been used as the name of a small tractor made by Modine.

The term "jeep" would eventually be used as slang to refer to an airplane, a tractor used for hauling heavy equipment, and an autogyro. When the first models of the jeep came to Camp Holabird for tests, the vehicle did not have a name yet. Therefore the soldiers on the test project called it a jeep. Civilian engineers and test drivers who were at the camp during this time were not aware of the military slang term. They most likely were familiar with the character Eugene the Jeep and thought that Eugene was the origin of the name. The vehicle had many other nicknames at this time such as Peep and Pygmy and Blitz-Buggy, although because of the Eugene association, Jeep stuck in people's minds better than any other term.

Words of the Fighting Forces by Clinton A. Sanders, a dictionary of military slang, published in 1942, in the library at The Pentagon gives this definition:-

Jeep: A four-wheel drive car of one-half to one-and-one-half ton capacity for reconnaissance or other army duty. A term applied to the bantam-cars, and occasionally to other motor vehicles (U.S.A.) in the Air Corps, the Link Trainer; in the armored forces, the ½ ton command car. Also referred to as "any small plane, helicopter, or gadget."

Early in 1941, Willys-Overland demonstrated the vehicle's ability by having it drive up the U.S. Capitol steps, driven by Willy's test driver Irving "Red" Haussman, who had recently heard soldiers at Fort Holabird calling it a "jeep". When asked by syndicated columnist Katherine Hillyer for the Washington Daily News (or by a bystander, according to another account) what it was called, Irving answered "It's a jeep."

Katherine Hillyer's article was published on 20 February 1941 around the nation and included a picture of the vehicle with the caption:-

LAWMAKERS TAKE A RIDE- With Senator Meade, of New York, at the wheel, and Representative Thomas, of New Jersey, sitting beside him, one of the Army's new scout cars, known as "jeeps" or "quads," climbs up the Capitol steps in a demonstration yesterday. Soldiers in the rear seat for gunners were unperturbed.

This exposure caused all other jeep references to fade, leaving the 4x4 truck with the name.

Willys-Overland Inc. was later awarded the sole privilege of owning the name "Jeep" as registered trademark, by extension, merely because it originally had offered the most powerful engine.

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The Jeep bearing the experimental vehicle number X-98 had flat fenders, but with a grille and hood not unlike the eventual CJ-5 grille. It may have been the first F-head-powered Jeep utility, built in 1949 or 1950 under Willys Engineering Release 5607. It had civilian features such as a tailgate, side-mounted spare, and "WILLYS" stamped on the hood, but photos indicate that X-98 was also tested by the military, perhaps several times. Photos taken in 1950 show it labelled on the bumper as X-98, whereas test photos from 1951 show it as vehicle 205. It was even referred to as the CJ-4M, although that designation seems to be more correctly belong to the slightly later military prototype. (Fred Crismon)

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The 4.0L inline 6 (I6) engine was introduced in the Cherokee in the late 80s and in the YJ in 1991. The cylinder design is based on the changes made to the fuel injected 2.5L I4 engine. The block and cylinder head are cast iron. It uses 7 main bearings and hydraulic lifters. The HP and torque gains are substantial over the older carbureted 258, but the peaks come at higher RPM. The fuel injected engine performs much better in off-camber, bouncy, and steep situations. It also calibrates better for changes in altitude. Fuel economy is also improved.

A good way to embarass yourself in front of your Jeeping friends is to refer to it as a V6. It isn't a V6, it is an inline 6 or I6. The "V" in V6 refers to the configuration of the pistons in the block. The only two V6 engines ever available from the factory in a Jeep are the 225 "Dauntless" Buick V6 in the late 60s and early 70s and the 2.8L GM V6 in 80s Cherokees and Comanches. If you are shopping for a Cherokee or Comanche, make sure you get the 4.0L and not the 2.8L engine, there is a world of difference.

The 4.0L engine used in the Wrangler from '91 until the present.

 

4.0L I6
Bore x Stroke	3.88" x 3.41"
Displacement	242 (4.0L)
Compression Ratio	8.8:1
Horsepower (net)	180@4750
Torque (net)	220@4000
Main Bearings	7
Valve Configuration	OHV
Fuel	MPI

The 4.0L I6 that is used in the XJ and ZJ is rated slightly higher than the YJ and TJ 4.0L engine probably due to a different exhaust system.

 

4.0L I6
Bore x Stroke	3.88" x 3.41"
Displacement	242 (4.0L)
Compression Ratio	8.8:1
Horsepower (net)	185@4750
Torque (net)	220@4000
Main Bearings	7
Valve Configuration	OHV
Fuel	MPI

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The AMC 360 was introduced in 1971 in J-series pickups and Wagoneers. It has a cast iron block and cylinder head with over head valves and hydraulic lifters.

In 1971, the AMC 360 have very high rating. I would assume these are gross ratings and the later are net ratings.

 

AMC 360 V8
Bore x Stroke	4.08" x 3.44"
Displacement	360(5.89L)
Compression Ratio	8.5:1
Horsepower (gross)	245@4400
Torque (gross)	365@2600
Main Bearings	5
Valve Configuration	OHV
Fuel	2bbl

In 1972, the 2bbl 360 is more conservatively rated, presumably these are net ratings.

 

AMC 360 V8
Bore x Stroke	4.08" x 3.44"
Displacement	360(5.89L)
Compression Ratio	8.5:1
Horsepower (net)	175@4000
Torque (net)	285@2400
Main Bearings	5
Valve Configuration	OHV
Fuel	2bbl

In 1973, an optional 4bbl carburetor was available. The horsepower and torque ratings for this version are significantly better.

 

AMC 360 V8
Bore x Stroke	4.08" x 3.44"
Displacement	360(5.89L)
Compression Ratio	8.5:1
Horsepower (net)	195@4400
Torque (net)	295@2900
Main Bearings	5
Valve Configuration	OHV
Fuel	4bbl

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The AMC 258 was introduced in 1971 in J-series pickups and Wagoneers and in 1972 in CJs. It continued to be used through 1990 in the Wrangler. It is basically a stroked 232 engine. The great thing about this engine is it reliable, inexpensive, and has horse power and toque peaks at low RPM.

The 258 inline 6 (I6) engine always came from the factory carbureted any many people complain about the Carter BBD carburetor and the maze of emmissions vacuum hoses. There are a couple articles below that can help you sort through those hoses and tune the Carter BBD. For a carbureted engine, the 258 with the Carter BBD performs very well off road. The 258 always came with a cast iron block and cylinder head, hydraulic lifters (with non-adjustable rockers), and 7 main bearings.

The 258 used in '87-'90 Wrangler YJs uses a computer controlled Carter BBD. It is very simlar to the 258 used in '82-'86 CJs, but performance suffers due to emmission controls.

 

AMC 258 I6
Bore x Stroke	3.75" x 3.90"
Displacement	258 (4.2L)
Compression Ratio	9.2:1
Horsepower (net)	112@3200
Torque (net)	210@2000
Main Bearings	7
Valve Configuration	OHV
Fuel	2bbl Carter BBD

The 258 used in '82-'86 CJs used a computer controled Carter BBD. The computer controls mixture based on an O2 sensor and other sensors.

 

AMC 258 I6
Bore x Stroke	3.75" x 3.90"
Displacement	258 (4.2L)
Compression Ratio	9.2:1
Horsepower (net)	115@3200
Torque (net)	210@1800
Main Bearings	7
Valve Configuration	OHV
Fuel	2bbl Carter BBD

The 258 used in '79-'81 CJs, some used a 1bbl carb and some used a 2bbl carb.

 

AMC 258 I6
Bore x Stroke	3.75" x 3.90"
Displacement	258 (4.2L)
Compression Ratio	8.3:1
Horsepower (net)	110@3500
Torque (net)	195@2000
Main Bearings	7
Valve Configuration	OHV
Fuel	1bbl and 2bbl

The 258 used in '72-'78 CJs, J-series pickups, and Wagoneers, some used a 1bbl carb and lower compression than later 258s.

 

AMC 258 I6
Bore x Stroke	3.75" x 3.90"
Displacement	258 (4.2L)
Compression Ratio	8.0:1
Horsepower (net)	110@3500
Torque (net)	195@2000
Main Bearings	7
Valve Configuration	OHV
Fuel	1bbl

The 258 was introduced in 1971 as the standard engine in J-series pickups and Wagoneers.

 

AMC 258 I6
Bore x Stroke	3.75" x 3.90"
Displacement	258 (4.2L)
Compression Ratio	8.5:1
Horsepower (gross)	150@3800
Torque (gross)	240@1800
Main Bearings	7
Valve Configuration	OHV
Fuel	1bbl Carter or Holley

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The "Dauntless" Buick 350 V8 uses a cast iron block and cylinder heads with overhead valves and hydraulic lifters. The Buick 350 was used from 1969 until 1970 in J-series pickups and Wagoneers.

 

Dauntless Buick 350 V8
Bore x Stroke	3.80" x 3.85"
Displacement	350(5.73L)
Compression Ratio	9.0:1
Horsepower (gross)	230@4400
Torque (gross)	350@2400
Main Bearings	5
Valve Configuration	OHV
Fuel	2bbl

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The British made Perkins 192 diesel I4 was optional in the CJ-5 and CJ-6 from 1961 until 1965. It uses a cast iron block and cylinder head with mechanical lifters and 3 main bearings.

 

Perkins 192 4 Cylinder
Bore x Stroke	3.50" x 5.00"
Displacement	192.2 ci(3.15L)
Compression Ratio	16.5:1
Horsepower (gross)	62@3000rpm
Torque (gross)	143@1350
Main Bearings	3
Valve Configuration	OHV
Fuel	diesel

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	Wrangler/TJ (1997 - present)  Windshield width 55". Round headlights. Center Tailgate mounted spare tire carrier with brake light. Tailgate opens to the side. Measures 81" from door hinge of vehicle.
	Wrangler/YJ ('92-'95)  Same as Wrangler models '86 1/2 - '91 except for extended rear sport bar.
	Wrangler/YJ ('86-1/2 - '91)  Windshield width 55", round fender Jeep, one piece windshield, factory roll bar with horizontal supports. Similar in design to CJ7, but with rectangular headlights and turn signal lights, and a squared off front grille. Comes with either half or full hard doors. Measures 81" from door hinge to rear of vehicle.
	CJ7 ('76 - '86)  Windshield width 55", round fender Jeep, one piece windshield, factory roll bar, bottom mounted windshield wipers, factory mounted door hinges, has either no windshield retainer or screw-in design. Door opening looks like a "U" rather than an inverted "S", measures 81" from door hinge to rear of vehicle.
	CJ5 ('76 - '83)  Windshield width 55", round fender Jeep, one piece windshield, factory roll bar, bottom mounted windshield wipers, factory mounted door hinges, windshield retainer screws on, sloped windshield. Measures 71 1/2" from door hinge to rear of vehicle.
	CJ5 ('55 - '75)  &  M38A1 ('51 - '71) Windshield width 59", round fender Jeep, one piece windshield, no factory door hinges, windshield retainer welded on vehicle, windshield at 90° angle to hood. CJ6 ('55 -'75) Same basic vehicle as an early model CJ5 except with an extended rear body rub.
	CJ3B ('53 - '64) Windshield height 22 1/2", hood height 10 1/2" (fender to top of hood), one piece windshield, has tailgate, bottom mounted windshield wipers, side mounted tire carrier (factory).
	CJ3A & M38 ('48 - '53) Windshield height 27", flat fenders, one piece windshield, vent in middle of windshield (factory), bottom mounted windshield wipers, hood height 6" (fender to top of hood).
	CJ2A & M38 ('46 - '49) Windshield height 25", flat fenders, split windshield, has tailgate, top mounted windshield wipers, side mounted spare tire (factory), hood height 6" (fender to top of hood).
	MB ('41 - '45) Windshield height 23", flat fenders, split windshield, no tailgate, recessed headlights top mounted windshield wipers, rear mounted spare tire (factory), hood height 6" (fender to top of hood).

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Need to know why that Check Engine light on the dash is glowing?  The light will remain lit until the problem is corrected and the code is cleared.  The codes below give an indication of the type of failure(s) and can be extracted using a SCAN tool. However, by doing an ignition key dance, you can place your 91-95 YJ into its diagnostics mode and extract the trouble code(s) from the PCM via flashes of the Check Engine light. Perform the following steps to extract the code(s): Without starting the engine, turn the ignition key ON, OFF, ON, OFF and ON. The Check Engine light on the dash will begin to flash. If any trouble codes are stored in the PCM memory, the CHECK ENGINE light will flash the number of the first digit, pause and flash the number of the second digit. For example, Code 51, Oxygen sensor - lean condition would be indicated by five flashes, pause, and one flash. A long pause will appear between individual codes if more than one code is present. Carefully observe the flashes and record the code. After the stored codes have been indicated (or if everything in the self diagnosis system is functioning properly), the Check Engine light will flash a Code 55. If the ignition key is turned OFF during the code extraction process and possibly turned back ON, the self diagnostic system will fail and must be restarted. If any trouble codes are stored in the PCM memory, the CHECK ENGINE light will flash the number of the first digit, pause and flash the number of the second digit. For example, Code 51, Oxygen sensor - lean condition would be indicated by five flashes, pause, and one flash. A long pause will appear between individual codes if more than one code is present. Carefully observe the flashes and record the code. After the stored codes have been indicated (or if everything in the self diagnosis system is functioning properly), the Check Engine light will flash a Code 55. If the ignition key is turned OFF during the code extraction process and possibly turned back ON, the self diagnostic system will fail and must be restarted.

Code	Code Name
11	Ignition
13	Manifold Absolute Pressure (MAP) Sensor Vacuum
14	Manifold Absolute Pressure (MAP) Sensor Electrical
15	Distance sensor or circuit
17	Engine running too cool
21	Oxygen sensor or circuit
22	Coolant temperature sensor or circuit
23	MAT sensor or circuit
24	Throttle Position Sensor (TPS) sensor or circuit
25	Automatic Idle Speed (AIS) circuit
27	Fuel injector control
31	EVAP solenoid or circuit
33	Air conditioning clutch relay
41	Alternator field
42	Automatic shutdown relay
44	Battery temperature sensor
46	Battery over voltage
47	Battery under voltage
51	Oxygen sensor - lean condition
52	Oxygen sensor - rich condition
53	Internal engine controller fault
54	Distributor sync pickup
55	End of Code output
62	Emissions Maintenance Reminder (EMR) mileage accumulator
63	Controller failure EEPROM write denied

Codes taken from service manuals.

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How to display the codes:

1. Turn the ignition key On - Off - On - Off - On within 5 seconds
    

2. Count the number of times the check engine lamp on the dash flashes on and off.
   
   The number of flashes represents the trouble code. There is a slight pause between the flashes representing the first and second digits of the code. Longer pauses separate individual two digit trouble codes.

Example: Lamp flashes 5 times, pauses, and flashes 5 more times. This indicates a code number 55. A code 55 will always be the last code to be displayed. This will indicate the end of all stored codes.

Also, the code numbers will be displayed on the vehicle's odometer. Each number will be displayed with a slight delay between numbers. Again, code 55 will always be the last code to be displayed. This method should work for Jeeps up to 1997.

Code	Description
11	No crank reference signal detected during engine cranking. Intermittent loss of either camshaft or crankshaft position sensor. CKP sensor target windows have too much variation.
12	Direct battery input to PCM was disconnected within the last 50 Key-on cycles.
13	No difference recognized between the engine MAP reading and the barometric (atmosphere) pressure reading from start-up.
14	MAP sensor input above or below acceptable voltage. 5 volt output to MAP sensor open.
15	No vehicle speed sensor signal detected during road load conditions.
17	Engine did not reach operating temperature within acceptable limits. Engine does not reach 20º F. within 5 minutes with a vehicle speed signal.
21	Upstream oxygen sensor response slower than minimum required switching frequency. Upstream oxygen sensor heating element circuit malfunction. Downstream oxygen sensor heating element circuit malfunction. Downstream oxygen sensor input voltage maintained above the normal operating range. Oxygen sensor voltage too low, tested after cold start. (Upstream or Downstream) Left oxygen sensor input voltage maintained above the normal operating temperature.
22	Engine coolant temperature sensor above or below acceptable voltage.
23	Intake air temperature sensor input above or below acceptable voltage..
24	Throttle position sensor input above or below acceptable voltage. TPS signal does not correlate to MAP sensor.
25	A shorted or open condition detected in one or more of the idle air control motor circuits. Actual idle speed does not equal target idle speed.
27	Injector 3, and/or 4, and/or 5, and/or 6 output driver does not respond properly to the control signal.
31	An open or shorted condition detected in the A/C clutch relay circuit. Insufficient or excessive vapor flow detected during evaporative emission system operation.
33	An open or shorted condition detected in the duty cycle purge solenoid circuit.
34	An open or shorted condition detected in the Speed Control vacuum or vent solenoid circuits. Speed control switch input below the minimum acceptable voltage.
37	Relationship between engine speed and vehicle speed indicates no torque converter clutch engagement. Auto. only.
37	An open or shorted condition detected in the torque converter part throttle unlock solenoid control circuit. (3 speed auto RH trans. Only). Incorrect input state detected for the Park/Neutral switch. Auto. only.
41	An open or shorted condition in the generator field control circuit.
42	An open or shorted condition detected in the auto shutdown relay circuit. An open condition detected in the ASD relay output circuit. An open or shorted condition detected in the fuel pump relay control circuit. An open circuit between PCM and fuel gauge sending unit. Circuit shorted to voltage between PCM and fuel gauge sending unit. No movement of fuel level sender detected.
43	Peak primary circuit current not achieved with maximum dwell time.
43	Misfire detected in one or more cylinders 1 thru 6. (4 and 6 cyls.)
44	Battery temperature sensor in voltage above or below acceptable range.
46	Battery voltage sense input above target charging voltage during engine operation.
47	Battery voltage sense input below target charging during engine operation. Also, no significant change detected in battery voltage during active test of generator output circuit.
51	A lean air/fuel mixture has been indicated by an abnormally rich correction factor.
52	A rich air/fuel mixture has been indicated by an abnormally rich correction factor.
53	PCM Internal fault condition detected.
54	No camshaft signal detected during engine cranking.
55	Completion of fault code display on Check Engine lamp.
63	Unsuccessful attempt to write to an EEPROM location by the PCM.
64	Catalyst efficiency below required level. (Same as code 72)
65	Power steering high pressure seen at high speed. (2.5L only)
72	Catalyst efficiency below required level. (Same as code 64)
77	Malfunction detected with poser feed to speed control servo solenoids.

 

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