Engine or exhaust noise

[David H. Brotemarkle CPA]

New to me 2008 Liberty Limited. Under load there is a rough noise that seems hard to recognize.
Engine has a slight tick on idle but I can’t tell where the noise comes from under acceleration. Foot off the gas and can’t hear the noise. Anyone else notice this? Normal or serious? No misfires or codes thrown. Other than the noise engine is smooth and plenty of power. Engine has 104,000 miles on it.

any ideas? Thanks.

ok, here might be a clue. Car was originally from Ohio. Checked under car and muffler looks somewhat rusted.

 

[David H. Brotemarkle CPA]

So I need everyone’s collective wisdom here. I put a new muffler on and the unusual sound is still there. I had a pretty good mechanic listen and he says it’s not rod knock, so that’s good, but he couldn’t tell what it was. When not under load there is no unusual sound. Accelerating, even at low speeds is when it occurs. Steady speed at 60 mph all normal. No knocking sound. What in the world is going on. Still sounds more like an exhaust puttering. Is there some sort of valve not operating properly?

 

[turblediesel]

Try taking a big wad of rags and momentarily blocking the exhaust. This trick makes any exhaust leaks louder. Might need an assistant on the listening or blocking end. Wear gloves, don't get burned. Don't block it for more than a few seconds.

 

[David H. Brotemarkle CPA]

So I need everyone’s collective wisdom here. I put a new muffler on and the unusual sound is still there. I had a pretty good mechanic listen and he says it’s not rod knock, so that’s good, but he couldn’t tell what it was. When not under load there is no unusual sound. Accelerating, even at low speeds is when it occurs. Steady speed at 60 mph all normal. No knocking sound. What in the world is going on. Still sounds more like an exhaust puttering. Is there some sort of valve not operating properly?

So I thought I’d bring everyone up to date. It may be important to others with these cars. JK and KK. I took it to my local small town mechanic to fix the a/c which was not working. He put a stethoscope all over the engine and informed me that the knocking was coming from the a/c compressor. At least he was 70% sure. I said how could that be when the a/c clutch was not working. Well he replaced the a/c compressor and now the engine with only 103,000 miles on it sounds like a brand new engine! So the bottom line is these engines are very sensitive. Good, but sensitive. I even was looking at how much it would cost to replace the engine. Now all good.

 

[John P.]

Glad you figured it out, I was going to say try a better quality fuel. My library absolutely hates gas from Sam's club pumps. It hesitates and doesn't idle happily and only gets 13 mpg with it. I put in good 100% gas and it runs great and mpg goes back to 16.7 in the city.