Engine still making loud knocking noise(sounds like a hammer on metal)

[1patriot]

Ok, I had a friend check for the codes because my check engine light came on again. I replaced the camshaft position sensor and the check engine light turned off. It came on again about 1 month later, a couple days after hearing a whistling noise during acceleration and after my car started shaking and idling roughly (my car turned off at a red light twice so far because of the idle going so low). The next day the engine started making a knocking sound every few seconds. Sometimes the knocks would come one right after the other (kind of like popcorn in the microwave). The knocking noise sounds like a loud hammer on metal. It doesn't necessarily always come right after I turn on the car..sometimes I have to let the car run for a couple minutes. My friend didn't give me the codes but said all the cylinders were misfiring and my O2 sensors were acting goofy I should change the air filter, fuel filter, mass airflow sensor, check for vacuume leak, change O2 sensors, and spark plugs. All of this has been done except I do not know if I checked everywhere for air leaks. After spending lots of money, I hate to go to the dealer! I need any other ideas?? Thanks!!!

[shunn]

shaking - rough idle - car stalling - whistling noise - misfiring - "goofy" o2 sensors. i'd venture to say you possibly have an intake leak and are running lean. there are are few places you can check such as the intake elbow, the air tube that goes from the idle air valve to the intake elbow. though it seems like a really big one, when i was having all of these issues changing my intake manifold gaskets cured all said symptoms.

It's really hard to confirm most of these without a proper smoke test which will show you any and all leaks. so unless you feel like throwing parts at your car, i'd take it in for a smoke test

[bmwdirtracer]

Wow, I'm truly sorry for your experience, and wish maybe you'd asked before you spent all that money.

Now, where do I start? How about where you started?

"ENGINE STILL MAKING LOUD KNOCKING SOUND...hammer on metal...

Therefore, you have a SERIOUS damned problem, and the car shouldn't be driven with such a sound!

Let's forget the cam sensor, apparently that was problem fixed.

Whistling, rough idle, dying are most likely an intake leak, likely meaning it's running lean on some cylinders, at least. So at this point you need a smoke test of the intake; there is no other reliable method of finding the leaks: none.

Then suddenly we got knocking: hammer on metal. Which is exactly where we stop driving the car. Shut off ignition, select neutral, coast to side of road. Immediately after scanning guages, preferably.

Then I REALLY begin to wonder:

Let me guess, your friend read mixture and misfire codes, then threw everything he could think of?

I will say this: the filters, PRIMARY 02 sensors and plugs are maintenance items, anyway. The MAF is what makes me think he's shooting in the dark, and I know many pro's who do the same, rather than testing. And of you run an oiled air filter, a failed maf becomes more likely. But that he let you get away with a visual inspection of the intake is silly, because you need a smoke test! And a fuel pressure test, too, fer Chrissakes. But nevermind.....


....because no-one's explained the damned metal-on-metal knocking! This is issue number one, and by far. Misfire doesn't explain it, because the dme will shut down that cylinder before detonation sounds like hammer-on-metal.

So I need you to tell me your mechanic's explanation for the hammer-on-metal sound, because everything else is secondary to that. I personally wouldn't throw a thousand dollars worth of parts at an engine which might have fatal damage: which is what I think of when you say "loud hammer on metal".

[325bob]

I suspect the noise is detonation, since its intermittent, a bearing noise wouldn't get better. A big vacuum leak is a probable cause.

[savannah996]

I suspect the noise is detonation, since its intermittent, a bearing noise wouldn't get better. A big vacuum leak is a probable cause.

ive experienced the knocking sound on my car. (which has an intake leak). In this case its a backfire through the intake. (put your hand on the intake and you should be able to feel it) this also goes away when the engine revs up. (if you have the same prob), it truly sounds like a hammer hitting a piece of galvanized steel, as for all the other stuff, ill leave it to the experts here.

[g00dwagen]

DISA valve fail.

That will be $100 sir

[1patriot]

Thanks everyone. I forgot to mention my fuel level gage shoots up than back down and back up again sometimes so I never really know exactly how much gas I have in the car...mabe that is due to the fuel pressure?? I will have the smoke test and fuel pressure test done and we'll see what they find. How much will these tests cost me..?

[1patriot]

what exactly is a DISA valve fail? will you tell me where it's located?

[bmwdirtracer]

Your guage movement is not related to fuel pressure, or your other symptoms.

I've never heard a DISA knock like metal, but I'm sure as hell willing to take goodwagen's word for it. Since the knocking happened after a spark-plug change, you might want to make sure they're all snug.

DISA is the rectangular box on the driver's side of the intake manifold, it adjusts intake runner length.

[ptarditi]

The PCV cyclone valve will can make a very metallic sound and would explain all the other codes you have. Also a jamming vanos unit can make rattling noises and usually gives a real rough start, if you're throwing parts the cyclone valve and the four accompanying hoses is the place to start. They are usually tested by checking vacuum pull at the oil fill cover. When I first heard the metallic sound on my wife's 330 I thought the worst it is a real nasty sound, its on the driver's side under the intake.

[beenthere]

Thanks everyone. I forgot to mention my fuel level gage shoots up than back down and back up again sometimes so I never really know exactly how much gas I have in the car...mabe that is due to the fuel pressure?? I will have the smoke test and fuel pressure test done and we'll see what they find. How much will these tests cost me..?

same thing happened to me knocking noise fuel gauge. Just changed fuel pump. Everything is fine now

[bmwdirtracer]

knocking noise fuel guage.

Welcome to the forum, beenthere, and Aloha from Maui.

The combination of these two symptoms does not give a diagnosible correlation, and might lead to an expensive misdiagnosis if they are accepted as truth. I'm NOT saying you're wrong, I'm just saying it's a rare failure, more likely to be related to a poor ground or unplugged fuel transfer hose (sucking jet pump), which was accidentally corrected during the pump replacement. (And that's assuming the knocking was an engine running out of gas). And I'm not so sure the level sensor and the pump even get their ground from the same place, either....they are completely separate circuits, as far as I'm aware.

I hope that you'll continue to visit the forum!
Aloha