exhaust thumping and a knock inside the block

[chriskarel]

Ok, all of a sudden my exhaust sounds like I have a cam installed. (the wom, wom, wom sound). There is also a pretty loud knocking in/near the block that matches the exhaust tempo. Just wondering what may be happening here. I'm going to scan my Haynes repair manual, but I wanted to ask you guys too. Thanks.

 

[BlkCurrantKord]

Well...first thought would be an exhaust leak.

 

[chriskarel]

haha funny you mention that. my header is cracked and I'm waiting on the replacement. However, I was informed that an exhaust leak wouldn't cause that.

 

[BlkCurrantKord]

Got me

 

[jeffpanya]

I get a weird ticking noise that goes away at times. Still don't know what it is could be similar...idk so if you find out let me know lol.

 

[nsjames]

A cracked manifold can make some strange noises. It will also affect your O2 sensor, so your knock might be detonation or soemthing caused by the F/A ratio being all jacked up.

Does it happen more so when hot? If so I'd say it could very well be manifold related.

Get a long screwdriver, and carefully use it like a stethoscope. Pay particular attention to the block and oil pan. If it's real loud touching the block with the screwdriver to your ear it might be internal. Have you drained the oil and looked for metal? You could also send an oil sample to Blackstone and have it analyzed, they'll tell you if it's high in any metals that would indicate excessive bearing wear.

 

[fastflyinaccord]

I get a weird ticking noise that goes away at times. Still don't know what it is could be similar...idk so if you find out let me know lol.

Might need a valve adjustment




OP, are you throwing a CEL?

 

[chriskarel]

Yeah, it's throwing the P0171. It comes on for a day then goes away for a few days.

 

[nsjames]

That's a system too lean code, and it might very well be because of your cracked manifold. Possibly also an intake manifold/vacuum leak. I'd get the exhaust fixed and see what happens as long as it doesn't sound like the knock is a rod or crank bearing.

 

[chriskarel]

ok thanks man. like I said I'm waiting for a new manifold. Would a week of driving lean do permanent damage to my engine??