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Discussion Starter · #1 ·
My YJ has a 2.5 motor and I have been having some problems since I bought it about 6 months ago. The motor will knock pretty loud while it is at idle, even when it is at running temp. Some days It feels like I have a 6 cylinder motor but then there is some days when I can barley get over 50 mph. It has a aftermarket cai and I recharged the filter and it did nothing. When I first got the jeep the motor oil was very black and old looking. The motor only runs at 125 degrees, and I thought that that was almost to low. This is the second motor and the previous owner told me that this motor has around 75,000 miles, The jeep has 185,000 miles on the rest. Any info would be helpful.
 

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engine temp way to low, should be closer to 185, in the way of your knock mine is doing the same thing and it's driving me nuts too. try running seafoam through it and clean it up and I also use lucus oil treatment in mine and it seamd to help a little. to find where it's knocking take a peace of conduit about 3 feet long and you can use it as a steathascope and maybe locate the knock
 

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First thing would be to change the thermostat with a fail safe at OE temps which I belive is 195 degrees. Then with the engine at the factory temps all the sensors andthe ECU can work the way they were designed. The ecu will optimize air/fuel mixture and from what you say improve the engine performance.
The 2.5 is known for noise in the valve train however PO may have neglected some oild change maintenance and may have some sludge built up. You can change the oil and substitute one quart of oil with some ATF and run it for 500 miles and then change the oil again. The ATF is a detergent and could clean it up some and maybe quiet the valve train a little. My n ew overhaul has a little noise with all new parts so it is normal for some noise.
 

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Absolutely, way too cold to be running properly. The computer is running the engine on preset parameters, which is basically closed loop. When it gets warm enough, it goes into open loop mode and begins relying on the host of sensors to appropriately adjust the parameters to better improve how the engine runs.

The preset parameters are there for warm up purposes, so that the engine can warm up quicker. Definitely get the internals cleaned out, ATF can work, so can engine flush, SeaFoam, as well as the other numerous types of sludge removers.
 

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What do you think that the temp. issue could be?
Sounds like there is no t-stat in the motor. YOu should have a 195 degree and the gauge will show 195-210 during normal operation.
You didn't state what year your YJ is.
There is a difference in the computers between the TBI and regular fuel injection among other things.
 

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Thermostat is only like $10 just go get a 195 thermostat and put it in and see if it helps. I put a 160 thermostat in mine and it never gets past about 150 so I have to change it back to the 195. Heater used to be so hot it was unbearable at times now it lows cold and sucks haha. I would start with a thermostat
 

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Ya it sounds like he needs a tstat and needs to pull the oil pan off and get some new rod/main bearings and rings for his pistons. Pretty easy and straight forward job just needs to make sure to gap the rings and plastigauge the rod/main bearings to make sure everything is ok.

What is your oil pressure at? And you said it has an aftermarket intake is there any oil coming out of it? Wondering if you have any blow by.

Could also do an oil change with some heavy duty diesel oil to see if the knock will go away. It has a ton of detergents in it and should clean a lot of stuff up. Just don't leave it in there for more than about 1k miles.
 

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Easy way to tell if the engine is heating up properly:

How hot is the heater?

Mine ran right around 125*F without a thermostat. The moment I put one in (and yes the system was bled properly of air) things started to overheat like crazy, blowing coolant out of the cap, temp gauge spiking to red (it never read anything before), and the heater blowing out fiery flames of air. Had to replace my water pump and radiator cap to solve the issue. Heater never worked before I put a t-stat in, always blew cold. And it wasn't plugged either, it didn't blow anything out of the cooling system when I flushed it.
 

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Discussion Starter · #19 ·
The heater blows out warm air but it will not force you to turn it off at all, when it is cold outside it is a cold ride inside the jeep.
 

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Probably a good indicator of it not running at operating temp. On a good day I got warm air, but now it pumps out quite a bit of heat. If my soft top didn't leak, and if I didn't have 2 AC holes cut in the firewall of my Jeep, then it would probably bake everything inside to a crisp.
 
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