2000 TJ 4.0 poor performance - JeepForum.com
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post #1 of 2 Old 03-21-2020, 04:58 AM Thread Starter
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2000 TJ 4.0 poor performance

I just rebuilt a 2000 4.0 TJ Wrangler junkyard donor engine w/100K miles on it. Replaced stock head with aftermarket 505 Performance head with 2 inch valves and Lunati cam has headers and cat converters with open exhaust, new piston rings , crank bearings, oil pump, spark plugs, water pump, clutch, pressure plate, t/o bearing. Jeep has about 300 miles on rebuild with terrible top end performance. Barely does 70mph and have to down shift on moderate grades in high gear also used a quarter tank of 93 octane fuel for 30 mile trip!

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post #2 of 2 Old 03-21-2020, 08:05 AM
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2014 JK Wrangler 
Join Date: Oct 2017
Posts: 7,579
hopefully you can check live data-
front o2 sensor voltage readings,
fuel trims,
Check 'sync' to see if in spec.

Then there is the wheel size to gear ratio issue...

When I see the price of OEM I think aftermarket.
When I see the quality of aftermarket I think OEM.
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