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Old 10-19-2012, 07:26 PM   #1
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2.5 liter motor problems?

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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Old 10-20-2012, 05:07 PM   #2
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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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Old 10-20-2012, 05:22 PM   #3
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What do you think that the temp. issue could be?
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Old 10-20-2012, 06:21 PM   #4
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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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Old 10-20-2012, 06:50 PM   #5
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I guess that I will change the thermostat and go from there
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Old 10-20-2012, 07:43 PM   #6
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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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Old 10-20-2012, 08:17 PM   #7
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Quote:
Originally Posted by theblackyj View Post
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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Old 10-20-2012, 09:09 PM   #8
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95 yj
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Old 10-20-2012, 09:23 PM   #9
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Theres no way...no way its running at 125. Id say your gauge is shot for one. Post a video of it running if you can and maybe we can determine what's wrong.
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Old 10-20-2012, 09:32 PM   #10
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I have no way of posting a video and it is saying that it is running at 125 even after a long drive.
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Old 10-20-2012, 09:35 PM   #11
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It should run 200-210 no matter what. There's not an engine I know of that runs that cool. Is it a bottom end knock or a top end knock?
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Old 10-20-2012, 09:38 PM   #12
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I have no way of taking a video and it is running at 125 even after a long drive.
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Old 10-20-2012, 10:25 PM   #13
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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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Old 10-20-2012, 10:53 PM   #14
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I will probably do that tomorrow
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Old 10-20-2012, 11:15 PM   #15
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It is pretty easy. Make sure to get some rtv sealant while you r at it so you don't get any leaks.
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Old 10-20-2012, 11:37 PM   #16
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I'd be more concerned with the knock than the tstat
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Old 10-21-2012, 05:47 AM   #17
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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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Old 10-21-2012, 09:25 AM   #18
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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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Old 10-21-2012, 09:59 AM   #19
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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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Old 10-21-2012, 11:49 PM   #20
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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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Old 10-24-2012, 01:40 PM   #21
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Any updates theblackyj?
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Old 10-24-2012, 02:10 PM   #22
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I have not really had time to mess with it but I have been driving it all week and it is weird because it seems like in the mornings it runs great but then on my way home is when it acts up. Someone mentioned about the oil pressure and I checked that and when it is idleing it is at at 30
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Old 10-24-2012, 06:05 PM   #23
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Anyone have any suggestions because these problems are starting to get old.
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Old 10-24-2012, 06:06 PM   #24
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Sorry I forgot to say that the thermostat is replaced and is not the problem.
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Old 10-24-2012, 08:52 PM   #25
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I hate to say it, but I was willing to bet anything that the Tstat had nothing to do with it. It's like putting you on cholesterol meds for a stubbed toe.

I've had a lot of 2.5s that blew up because of the rods. I would venture to say if its not in the valve train it's a rod or rod bearing
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Old 10-24-2012, 08:57 PM   #26
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Well I guess that there is a plus side to the motor in your jeep blowing up or quit running Time to upgrade to a bigger motor.
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Old 10-24-2012, 09:05 PM   #27
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You could try some thicker oil and or some Lucas oil stabilizer. But, thats gonna mask it for a little while if it does anything at all. I honestly think your gonna have to pull the pan and have a look around. Another thought I just had is it could be the water pump, power steering pump, or alternator. Before I did anything else, I'd pull the belt off it and start it to see if the knock was still there. Don't drive it like that though
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Old 10-24-2012, 09:21 PM   #28
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I have no choice but to drive it.
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Old 10-24-2012, 09:36 PM   #29
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I meant don't drive it when u take the belt off.
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Old 10-25-2012, 02:22 PM   #30
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Ok

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