2000 TJ poor performance after rebuilding donor engine

[bobalou2]

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!

 

[Goatman]

Timing issues can happen when going with a 'performance ' camshaft. They are made to perform inappropriate certain rpm range and some tend to fall off quickly when outside of that range. Have you thrown any codes? If you accidentally got the timing chain off by a tooth, which can be fairly easy to do higher rpms can suffer. It's also possible to get the spark order mixed up. These engines can still run (even pretty smoothly) when the firing order is off. I had a CJ-7 I got cheap because it ran like crap above 3500 rpm. Turns out the whole firing order was 1 off clockwise on the distributor cap. But it idled good!? Rocker arms can be off on a valve. Basically double check everything. It is amazing how a straight 6 can be so wrong and yet still run well enough to never think these could be off.

 

[dbbd1]

What was your MPG before the rebuilt engine?
What is your gearing?

 

[Chris]

Have you had it tuned via HPTuners to adjust the timing, fuel, and everything else they should be compensated for with all those performance mods? Have you used HPTuners to disable the post-cat O2 sensors so they aren’t providing feedback the the PCM?

If you haven’t done all of that, no wonder it’s running like shit.

 

[bobalou2]

What was your MPG before the rebuilt engine?
What is your gearing?

What, where is HP Tuners, PS I live in rural Ky and never heard of this place or thing.... I just want my Jeep to run better after spending all this money . My original 2000 TJ engine ran great until a piston

Have you had it tuned via HPTuners to adjust the timing, fuel, and everything else they should be compensated for with all those performance mods? Have you used HPTuners to disable the post-cat O2 sensors so they aren’t providing feedback the the PCM?

If you haven’t done all of that, no wonder it’s running like shit.

What, where is HP Tuners, PS I live in rural Ky and never heard of this place or thing.... I just want my Jeep to run better after spending all this money . My original 2000 TJ engine ran great until a piston cracked at 345K miles.
cracked at 345K miles.

 

[Chris]

What, where is HP Tuners, PS I live in rural Ky and never heard of this place or thing.... I just want my Jeep to run better after spending all this money . My original 2000 TJ engine ran great until a piston

See this thread: 97-06 Jeep Wrangler TJ ECU / PCM Tuning Options

The ONLY way to get your TJ running right is to tune it. There's no way it's going to run correctly with the factory PCM settings and the mods you've done to it.

 

[por212]

Which Lunati cam are you running?