loud knock from exhaust and smoke.. thoughts

[Tommygun_98]

So I had a rough idle and A LOT of smoke coming from my exhaust, read my CE codes and I had a bad coolant temp sensor and an EGR fault. I replaced the sensor and I font have a rough idle and my smoke eased off quite a bit. However now I have a loud knock from my exhaust.. almost sounds like a metal dent being pushed back into place, and it happens every 3-7 seconds, I also still have that smoke problem. I took my EGR valve off and it seemed to work properly, I could shake it and hear a fair amount of carbon build up. Any body got some thoughts? The best thing I can do is replace the valve and see what happens but I'm flat broke at the moment.

[1badchicken]

What year is it

[Tommygun_98]

What year is it

95 , forgot to mention that

[BLACK-HAWK]

spark plugs and wires, O2 sensors ..?

[Tommygun_98]

I'll look into that, but if it were kicking because of spark plugs I think codes should have come up. I plan on replacing the o2 soon. Like I said its a fairly loud bang, like someone kicking my muffler. Is it possible to smoke up if something was up with the exhaust system other than the EGR?

[Scott Chab]

Smoking wouldn't be caused by the exhaust system and the only noises that could be coming from the exhaust would be due to catalytic converter matrial breaking apart and rattling, a loose heat shield rattling or some other loose part.

Do you hear any strange noises at the motor?

[96AZHAWK]

Is most everything on the car stock? Did it just start acting up all of a sudden?

[Tommygun_98]

Yes everything is stock, I was having an overheating issue but I fixed that. When this first started there was a rattle somewhere under the hood but that went away quick. I'm kind of leaning twords head gaskets or bad cylender valves.. is there anything besides engine internals thah can be causing this smoke? I've heard of EGR valves causing you to run lean, cause knocking and larger emissions, but I have a fair amount of smoke coming out of my exhaust and it just doesn't seem like an EGR problem.

[Tommygun_98]

Okay there is a clingity clang under the hood, I sounds like its coming from between the front of the block and the waterpump. Also the knock eases away after driving it for a bit. I checked my coolant levels, still good, and my oil looks fine and brown.

[Tommygun_98]

*the knock in the muffler..

[lakeratiam]

Is the "smoke" blue, white or black? Can you smell gas . oil burning or anti freeze? all bolts on the water pump pulley good to go?

[96AZHAWK]

I have rarely seen the EGR valve (doohicky on the rear of the intake manifold) affect a car very much at all, especially to the point of knocking or clingity clacking? Let's see about breaking it down... no guarantees this info will help at all. hahaha

EGR would cause a lean condition if it was not sealing or messed up in a way that it would allow un-metered air into the intake manifold.

Blown head gaskets would either allow coolant into oil (result in a non-delicious form of chocolate milk), or coolant into the cylinder (causing steam-ish out of the exhaust and would also do an awesome job of cleaning your piston), or the cylinder would pressurize the coolant system (and would cause overheating).

Bad valves could either hang up in the guides, not seat properly and cause a lack of compression in a particular cylinder or cylinders. Bad valve SEALS or worn valve stems would cause oil to drip into the intake or exhaust ports of the cylinder and would burn off somewhere resulting in smoke. TYPICALLY does not make it run too much worse unless it is leaking a pretty good amount of oil into the intake port/combustion chamber.

I do not believe 95 and older cars had misfire detection (no crank reluctor/crank position sensor).

I am curious about the reading of the pre-cat and post-cat O2's and cylinder compression. That could help nail down what is wrong with the way it is running. FWIW... checking cylinder compression with stock manifolds... not the funnest time in your life.

[BLACK-HAWK]

exhaust manifold gasket? notorious intake manifold leak?

[Tommygun_98]

The smoke is white and plumes out at idle, sometimes it won't, it smells like straight up heavy exhaust. I'm going to take it for an engine pressure test, I think that should detect whatevers going on. I'll keep you guys posted about the muffler knock, because I've never heard something like this before. thanks for your guys insight. And my water pump does not run on a pulley/belt.

[BLACK-HAWK]

at idle, do you hear a ticking sound coming from the engine bay? If so, you just might have a bad exhaust manifold gasket. You can also remove the valve covers and inspect the valve springs for damage.