Rod knock??? Did I buy a lemon???

Hi, I'm new here. Searched on here lots, you guys have been very helpful. I'm hoping you can help me some more as I'm really starting to regret buying my KJ. I though I'd get something newer to be more reliable than my 88' Toyota 4x4, not sure I got what I wanted.

I just bought a 2003 Liberty Sport 4x4 with the 3.7 & automatic a couple days ago. Since I'm pretty mechanically inclined, I figured I'd be ok to look the truck over myself instead of take it to a mechanic before I bought it, stupid me I think.

What I didn't notice at the time is a rattling sound possibly coming from the bottom of the engine. After experimenting with what makes it happen, I noticed that with it shifted in first gear, when I am accelerating there's not much noise, but when I'm coasting in first gear from high RPM the noise is quite distinct all the way down to an idle then it pretty much goes away. It's quiet under power but noisy when coasting. It'll also do it always when you push the gas to get started from a stop but then goes away after it gets moving. I don't really hear it when it's idling, and it's much quieter when the engine is cold. You can't even really hear it from the top under the hood, it's definitely coming from underneath the truck. I thought it might be something loose in the drivers side exhaust but it's weird that it doesn't always do it.

Also got a P0133 code from a surprise CEL that came on 2 days after the purchase... they must've reset the computer to trick me. Looks like that's the drivers side O2 sensor before the cat right? Should I just swap it out?

Needless to say I'm NOT a happy guy right now. :favorites68: Thinking I might be better off to just find a telephone pole on the side of the highway and let my insurance company deal with it!!! LOL p:

Welcome to forums GTF.
How many miles are on this 03 KJ?
Without being there it is hard to say, so getting it into a shop for inspection would be a good idea.
I would Start by lifting the hood in Park and advance the throttle (at side of throttle body) up & down, and see if you can hear the rattling sound.
Generally if it is an engine rod knock, you will hear it even without a load. Try running a higher octane fuel if you think it may be detonation.
It more sounds like a rolling noise or front driveshaft/cv's rattling or even a suspension component? Any oil leaks, CV boots dry, fluid in transfer case up?
Click on photo to see video of passenger side CV can rattle.
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1st gear, high rpm, coasting, description is confusing. Are you in neutral when coasting< does sound /rattle stop in neutral?

i agree sounds like suspension noise, hub bearings, half shafts, front drive shaft. etc...

LibertyTC said:

Welcome to forums GTF.
How many miles are on this 03 KJ?
Without being there it is hard to say, so getting it into a shop for inspection would be a good idea.
I would Start by lifting the hood in Park and advance the throttle (at side of throttle body) up & down, and see if you can hear the rattling sound.
Generally if it is an engine rod knock, you will hear it even without a load. Try running a higher octane fuel if you think it may be detonation.
It more sounds like a rolling noise or front driveshaft/cv's rattling or even a suspension component? Any oil leaks, CV boots dry, fluid in transfer case up?

1st gear, high rpm, coasting, description is confusing. Are you in neutral when coasting< does sound /rattle stop in neutral?

Click to expand...

Truck has about 130,000 miles. There's a good shop next to my work that I will have look at it on Monday.

Sorry if it was confusing. I'll try to clarify. The noise is still there in Park. if the engine is revving but not under any kind of a load it makes the rattling noise. It sure sounds to me like some kind of metal to metal noise, it's a very fast rattle at higher rpm and slower at lower rpm. It is definitely directly affected by engine rpm, not speed of the vehicle. I don't think it's the transfer case as it seems localized to the area at the back of the engine or front of the transmission.

What I meant with the coasting thing is this. If I put the truck in first gear on the auto transmission and accelerate, I don't hear it much as I'm speeding up, but when I get it up to higher rpm and start to slow it down like you might do going down a steep hill, the noise is loud and constant all the way down to an idle unless you give it gas again. That is part of what makes me think it might be something major from the bottom end of the engine.

I know this isn't much to go on, but I appreciate the help anyway. I guess I was hoping that this was sort of common and easily repaired. I'll look at the things you two mentioned, but since the noise is there when stopped as well I'm still thinking the worst at this point. I'll see if I can figure out how to post a vid of it on here later.

At that mileage the valves/seats etc can need some work, but the bottom end is normally real solid unless it was run low on oil. That is the problem when buying a used KJ, you never know the "real" history.
Because if the CE light relating to sensor, it may alone be effecting cat or engine running condition/performance. Good Luck, I hope it is not a major rebuild, and please post back you findings after shop on Monday.

Here's a link to a video I took of the noise.

http://www.youtube.com/watch?v=T9DTz3-Dox4

This is at idle. I put a stethoscope all around there and it seems louder around that mini cat in the picture, I can hear it clearly through there. If it is the cat rattling though it seems strange that it doesn't do it all the time.

Anyway, I'll post back when I know more.

ive heard something similar before on my step sisters car. exhaust donut between the exhaust manifold and the mid/cat pipe maybe? do our libertys have those?

Sounds like some kid threw in a broken marble into your Cat or exhaust pipe!

Check to see if your cat shields are not loose/broken weld and rattling around.....just a thought. I had this happen before but not the KJ but it can happen on any vehicle. Real simple fix so I hope that might be it.

Dave

Does not sound like rod knock.Could be the cat coming apart,could be something in the bellhousing,or like stated a loose heat shield.

The 1st thing I would do is check the exhaust manifold heat sheilds,cold engine,by grabing them and see if they move to much.The 4.7's have a issue with the back(most rearward) manifold bolts breaking due to a single material gasket.Easy fix,just takes a little time.Use only OEM gaskets and all brand new OEM bolts(only palce to get the bolts is the dealership).

If not that then undue that exhaust clamp about the cat and the one below,remove cat and see if anything falls out.No worry about gaskets or the like as there is none,the upper clamp takes a 10mm wrench and a short 10mm ratheting wrench is worth it's weight in gold here.Can try and start the engine with the cat removed to see if the noise is still there,if gone it's a bad cat,if not then move to the next part.May have a few codes set if you run it without the cat.

If not the above 2 then remove the bell housing inspection cover and have a look around in there.Could be loose flex plate bolt or one that came all the way out and it rattling around in there.

If not

had similar noise, was the drivers side cat coming apart. Could hit it with my fist and it would rattle, but at first I thought the bottom end of mine was coming out!

mmm... I like the cat converter explaination. I've had a couple cars have that happen over the years.

Me too. My Ranger did that.

Wow, thanks for all the responses guys, much appreciated. I guess the video was a little better than my shoddy description of a random sound!

I sure hope it's the cat. I'll be sure to let you guys know what I find out.

My mom's Kia is currently making a very similar noise. It's definitely the catalytic converter.

Yeah, sounds like gravel in the cat.

Decided not to take it in as I'm usually a DIY kind of guy. Pulled the bottom pipe off the cat and beat on the thing with a rubber hammer. I can definitely hear some of the innards rattling around in there. Sure is a strange noise. I must say I'm a little embarrassed that I thought it was a rod knock, man I was way off!!!

Now I just have to find a replacement, that noise is really annoying.

Anybody got any idea if a broken cat could cause that P0133 code I was asking about? I'm thinking it would be a good idea to replace that upper o2 sensor if needed when I replace the cat since it has to come out anyway.

GTF said:

...Anybody got any idea if a broken cat could cause that P0133 code I was asking about? I'm thinking it would be a good idea to replace that upper o2 sensor if needed when I replace the cat since it has to come out anyway.

Click to expand...

That code is related to a bad O2 sensor - shoot, your sensor may have come apart and that's what is rattling around in the downpipe/cat!!! :smokin:

Seems like your noises and codes are all related...

Bob

^^ this.

if you've pulled the pipe off the cat, why not go a step further and pull the cat off completely and see what falls out?

Agree with the others after listening to the video several times - sounds like something loose rattling in or on the exhaust system or bell housing.

I've encountered an engine with bad rod knock before - that later threw # 3 cylinder thru the side of the motor. Believe me, there would be NO DOUBT in your mind if it was rod knock. From what I heard, this isn't it.

Said you had a code on one of the O2 sensors? Same side exhaust? Hmmm, perhaps something broke off of the O2 sensor and is rattling around in the exhaust pipe? Or the O2 sensor code is a symptom of something being wrong/broken loose inside the cat or exhaust pipe?