Engine swap stumbling badly 2002 KJ 3.7 2 Whl

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cruisingram2000

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I picked up this 2 wheel drive 2002 LIberty with a bad motor- just so happened I had a 2002 3.7 sitting in a wrecked liberty for about 4-5 years. So we stabbed this motor in, got it running. It is running rough- not sure exactly why, but it seems like it is starving for fuel, when you give it gas, it actually slows down the engine, you kinda have to feather the gas and get it coming up in RPM slowly. I got a couple coil packs from the parts store during the test drive, because one pack was pretty marginal when I put it in. It feels as though it is a fuel starvation problem though. I have one code coming up, the EVAP thing in the back- would this do it? The vehicle it came out of and the one it went into had some old fuel in the tank- another hint. Is there a fuel filter in the tank that may prevent enough fuel from getting through? Where are all the fuel filters on this thing anyway? I am a bit new to the libertys, but it is my wife's favorite ever, her last one gave up the ghost 5 years ago, and she has wanted the same one every since- and I happened upon this one , nicer all the way around that the last one even.

Some ideas?
 

Muddy

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When mine acted like this it was a clogged catalyst on the passenger side. Do your plugs look dirtier or darker on one side of the engine vs the other? I drilled a small hole just upstream of each cat and used an endoscope to look inside, one of them was all broken up and clogged in the front. In my case caused by running with a bad O2 sensor for too long.

The fuel filter is mounted outside the tank, just forward of it. It can be changed without dropping the tank if you suspect it, but there is also a fuel pressure test port on the fuel rail on the passenger side. You can test fuel pressure if you suspect a clogged filter or weak pump.
 
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cruisingram2000

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When mine acted like this it was a clogged catalyst on the passenger side. Do your plugs look dirtier or darker on one side of the engine vs the other? I drilled a small hole just upstream of each cat and used an endoscope to look inside, one of them was all broken up and clogged in the front. In my case caused by running with a bad O2 sensor for too long.

The fuel filter is mounted outside the tank, just forward of it. It can be changed without dropping the tank if you suspect it, but there is also a fuel pressure test port on the fuel rail on the passenger side. You can test fuel pressure if you suspect a clogged filter or weak pump.
Thanks, this is all helpful stuff
 

cruisingram2000

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Follow up- so changed all the spark plugs and a couple coil packs- ran great for a few minutes, then stumbling again, now I get the P0303 code. I think I may have bad Cats- anyone?
 

Ksat

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I don't think a clogged cat would cause a misfire.

If you have a scope, you could back probe both the injector and ignition coil and compare waveforms to another cylinder. Checking compression on 3 wouldn't be a bad idea, either. If you don't have a scope, take a resistance reading on 3's ignition coil and injector and compare to anther cylinders. If they check out, you can try swapping the ignition coil with another cylinder, erase the code, then see if the code changes. If it doesn't, do the same with the injector.

If you have a capable scanner, check what the fuel trim is at idle. Checking other data PIDs while you're in there- such as MAP, IAT, etc.- would also be a good idea.

If you think you have a restricted exhaust, you can remove both O2 sensors and see if the condition improves. You may also want to check fuel pressure, as the symptoms you described could be caused by that, as well.
 

Muddy

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I don't think a clogged cat would cause a misfire.
It did for me. P0300 code and severe loss of power anytime I gave it more than gentle throttle. Fuel trims were out of wack on one side even after all new 02 sensors too. Cat was basically gravel inside.
 

Ksat

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It did for me. P0300 code and severe loss of power anytime I gave it more than gentle throttle. Fuel trims were out of wack on one side even after all new 02 sensors too. Cat was basically gravel inside.

Shows you what I know :) .
Thanks for that. I looked it up and you are indeed correct.
 

cruisingram2000

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Gotta love this- had a brand new, faulty coil pack! On a hunch, I am like WTF. So I grabbed another coil pack, put it on #3, and boom, runs great. Glad I have a good relationship with my ORielly's guys, took it back and said dude, this thing was bad out of the box- they refunded me no problem. Usually can't take back electrical stuff like that.
 

dtennes

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If you need any kind of sensors, injectors, electronics, etc... and you are unfamiliar with Quadratec, recommend that you go here...

https://www.quadratec.com/

...they sell nothing but top-shelf OEM parts that are 99.999% Mopar equivalent and reliable. If you use them, look up the recognized Mopar part number on one of the Mopar part websites and then use it as search criteria on Quadratec.
 

cruisingram2000

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Thanks- I love quadratech for a variety of reasons LOL. So, I have two codes to clear, minor, and get the AC going and then I will get some old man emu shocks and springs, and this thing cherry brah! I noticed that the fuel filler area is loose and suspect my 1494 code is coming from that, and my other code, 0404 or something like that is obvious, the bolts were not good when I put on teh cat converter and it's a bit loose and rattly, and will tightent htat up this weekend. The AC controls had problems, so I just got a new set in from ebay, and the system is holding pressure but the compressor is not turning on.
 

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