I have been lurking for some time doing research on buying a crate engine. Being in Australia this was a major investment especially since I purchased the engine from the US. Now that it is installed I have a problem with the engines and I am at a loss as to what the problem is. I have read several posts with similar problems but have yet to find an answer, so I need help into what to look for. I am not a mechanic but my mechanical ability is not too bad.
My Jeep is a 1999 automatic Cherokee Sport with the following modifications, including parts installed to find the problem:
Mild cam (all I know is that it is comp cam)
Spectre air filter/snorkel (not cowl)
63mm bored throttle body
2.5” high flow cat back exhaust
New fuel module
All new sensors except oxy sensors
New ignition system including dizzy, pulse ring, plugs, leads and coil
New radiator including separate transmission cooler with fan
Water pump, thermostat and housing
The problem is a high rev power loss (sound familiar). Around 4,000 to 4,200rpm the engine looses power and struggles to rev to redline. Here it eventually changes gear and runs really rough for a little bit, then you can feel the power build back up until you hit the 4,000 mark again.
The problem does not happen when the engine is cold. When cold it will run really well and rev out completely. Also it seems to only do it under load.
I have tested the engine compression and this checked out good.
I have tested the fuel pressure with the old fuel module and at idle running it was a 49psi. When the engine suffered it’s problem it did drop to around 39-40psi. While running rough it ran at around 46psi.
It has been on two dynos, the first was a waste of time. They claimed valve float, which I am pretty sure it isn’t, and the engine builder is confident of this too.
The second dyno was done for free by another company so i don’t have any reports, but he believed that it is dumping massive amounts of fuel when in open loop and WOT and causing the engine to run way too rich.
I have tried a map adjuster recently as well. I had it dialed back to 4 volts and the problem still persisted. I have even tried the stock 22.5lb injectors and the problem still persisted.
I am now posting this to get some help from you guys as it is really giving me the s%$^s!!
Any help would be appreciated!