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Thread: WHAT SPARK PLUGS DO I NEED? 1990 XJ

  1. #1

    Default WHAT SPARK PLUGS DO I NEED? 1990 XJ

    What is a good spark plug for the 4.0 JEEP CHEROKEE?

    What is the reccomended gap?

  2. #2
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    Champion Gold Truck Plugs, part # 4412. Gap is .035.
    1998 XJ Classic: 5" w/ 35" MT/R's
    1998 ZJ: 2" w/ 31" Trxus MT
    Big, Bad Jeep Pics

    Rock Lizard Fabrications ...Offroad Armor that's "Tough As Scales"

  3. #3
    Airborne Janitor SyCo's Avatar
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    I'm partial to NGK V-Powers myself, part #NGK-7252
    98 4.0L XJ Sport, NP231 with SYE, AX15
    5" RE/DPG extreme duty lift, 33x12.50 Goodyear MT/Rs
    D30/D44, 4.56 gears, Auburn ECTED, four wheel disc brakes

  4. #4

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    ANYONE USE AUTOLITE?

    I like autolite - but don't know where to gap em?

  5. #5
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    in my experience autolite are junk, economy plugs, I'd stick with V-powers or truck plugs, the truck plugs last forever.
    MJ 'manche, 4.0 5-speed 4wd, dana 44, SOA convertion rear, 2" spacers front, 33x12.5 baja radials

    80 CJ-7 258-t176-D300
    the new toy bone stock and staying that way for awhile.

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    I have always loved Autolite Platinums in all of my other cars but i have never had them in my Cherokee. i have Champion Truck plugs right now and they work grreat.
    97 Jeep Cherokee, 4.0L, 5 Speed,Hurst Short Throw Shifter, Flowmaster 40 series, K&N FIPK, Firepower Ignition, American Racing 767 w/ 225/75/15 Bridgestone Dueler A/T

    "Never underestimate the power of the Jeep."

  7. #7

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    I went to look at plugs today and they don't have my year cherokee (1990)...


    I looked at the difference on the stock 1990 and 1991 plugs and the 1991 plug electrode sticks out about .75" from the tip of plug where the 1990 has only about .25" sticking out the end...


    DID JEEP CHANGE HEADS?
    What is the difference in 1990 and 1991? are the plugs all the same on all year cherokees?

    CAN SOMEONE GIVE ME AN ACCURATE PLUG TO USE ON 1990 XJ?

    thank you...

  8. #8
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    I have Champions gaped at .35 in my 90.
    78 CJ5, 232 3 sp, RED, lift with 31's.
    05 TJ, 258, auto, Orange, lift with 31's.




  9. #9

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    Thats great that you use champions gapped at .035 & all but my question is:


    ARE ALL YEAR CHEROKEE PLUGS THE SAME? (4.0L)

    because at the part store a 1990 Cherokee/XJ lists a 4430 part # which they don't stock. The 1991 Cherokee/XJ uses a ???? part # which they do have.

    When I pulled the stock plugs for 90 & 91 the difference was immediate.

    The 1991 plug electrode hangs down 3/4" more than the 1990 plug.



    WHY ? & CAN I STILL USE IT?

  10. #10

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    4.0L I6 EFI "Power Tech" - 177 hp @ 4750 rpm, 220 ft lb @ 4000 rpm - used 87-90
    4.0L I6 MPI "Power Tech HO" (High Output) - 190 hp @ 4750 rpm, 220 ft lb @ 4,000 rpm - used in 91-95

    I'm not sure what changed in 1991 to make the engine "High Output," but I would assume the spark plugs are different for a reason. I looked up the part number for my 1989 cherokee and it was 4430.

    Hope that helps.

  11. #11

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    oh? so I don't have the 4.0 HO? Is my I6 inferior to the HO motor?
    I feel like **** now, I thought I bought the good jeep (with the I6)... Now your telling me there are 2 different I6's...

    DAMN, I WAS 1 YEAR OFF!!!


    But this is starting to make sense then...


    It seems as though 8?-90 used a smaller length spark plug, or the spark plug hole on the head was a short/quick distance from the top of the cylinder ;

    whereas in 1991+ it looks like the hole for the spark plug is higher, or further away(longer run) from the cylinder...


    Not sure why the further away improves performance, but it is probably a combination of that and a few other things...

  12. #12
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    Pick up some NGK 7252s...if you cant find them locally, carparts.com has them (except you have to buy in quantities of 4)..
    97 Tacoma...I miss my XJ

  13. #13
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    Actually don't knock the 4.0 you have. It comes into it's torque much lower in the RPM band than the 4.0 HO So it has a bit more tourqey feeling to it, just not the high end horespower. Still a very good engine.

    '87-'90 XJ: 177hp at 4500rpm, 224lbft at 2400rpm, redline 5000rpm
    '91-'95 XJ: 190hp at 4750rpm, 225lbft at 3950rpm, redline 5250rpm
    '96-'99 XJ: 190hp at 4600rpm, 225lbft at 3000rpm, redline 5300rpm
    '00-'01 XJ: 193hp at 4600rpm, 231lbft at 3000rpm, redline 5300rpm

    The '87-'90 engines had Renix electronic multipoint fuel injection, electronic ignition, a single 51mm (2.0") throttle body, and a rather inefficient low port cylinder head.
    In 1991 engines received Chrysler sequential MPFI, a larger 60mm throttle body, revised intake and exhaust manifolds, and a more efficient high port cylinder head. As a result, these engines produced 13hp more than their predecessors and gained the "High Output" designation.
    In 1996 engines received noise, vibration, and harshness fixes. The blocks were stiffened with extra ribbing, a main bearing brace was added, and lighter cast aluminium pistons were introduced to reduce cold start piston slap. Engines also received revised camshaft timing for more low rev torque.
    In 2000 a distributorless coil-on-plug ignition system was installed, intake and exhaust manifolds were revised, and a more efficient water pump was included.
    1994 YJ soon to be LT1 350 and SOA

    1988 Cherokee Laredo 4.0L Auto Still working on it.

    1991 4.0 HO Comanche, stock(for now)

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