4.0 Wrangler Lacking Grunt - Jeep Wrangler Forum

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Old 06-23-2013, 01:37 PM   #1
Maverick1066's Avatar
Join Date: Jun 2013
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4.0 Wrangler Lacking Grunt

Just bought my beast off Ebay -great fun vehicle, tidy mechanicals, Full Years NOT, wax-oiled and good chassis etc,,

Just a Tad disappointed about the power ( for a 4.0L), does not pick up very smooth through the gears, and 5th is for downhill only!

Have ordered a 'Service kit' to start with: Plugs, leads; dizzy cap; rotor etc, but would appreciate any help here as to where to go next.

Have read about the intake airbox, possible K&N Conversion kit ?

Thanks in advance for any suggestions

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Old 06-24-2013, 07:50 PM   #2
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I did the K & N, chipped it, and did some throttle Body work and exhaust work and got about 15% all with cheap bold on stuff! Jeep seems to flat get with it here in Northern Nevada and really good Off Road, gas mileage sucks cuz I put my foot in it a great deal, Good Old School jeep.

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Old 06-26-2013, 10:18 AM   #3
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what tire size are you running, and what's the gear ratio in the axles? how about transmission, and year of vehicle?

FWIW, the main things you can do to the 4.0L to gain real horsepower and torque numbers, include adding forced induction (supercharger/turbo), a stroker (4.2L/4.0L hybrid engine), or head/cam/valvetrain work. all those will also need a piggyback ECU & dyno tuning.

if you have larger than stock tires, you need to regear the axles to put the engine back into it's powerband. even with the above mods, or a V8 swap, you still need proper gearing.
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