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Old 05-26-2008, 04:56 PM
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Cool Running Rich/ Weird Exhaust Noise

the noise sounds like a ticking noise when the engine is idleing...im new to these cars so it might be normal but i wanted to see what is up with it....i also seem to be running rich (no check engine light though) it smells really strong out of the exhaust...i changed the plugs with bosch platinum plus 4's and put new coil packs in and its still the same and i pulled them out today and they all look the exact same...none wet etc...

heres a video of the above mentioned noise
100_2736.flv - Video - Photobucket - Video and Image Hosting
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Old 05-26-2008, 06:13 PM
 
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I could not hear anything from the engine, but that exhaust is very odd and sounds scary. It sounds like you have an exhaust valve that is badly burnt or bent. You seem to be idling on 5 cylinders. One plug should look bad.

If the sound you hear under the hood is a mechanical ticking, the problem could be at the cam rather than at the exhaust valve.

If the sound you hear at the engine is an exhaust leak from the exhaust manifold or manifold gasket, then it could be a bent exhaust valve. Big leaks near exhaust valves can bend them due to sucking in cold air when you take your foot off the gas. The cold air comes in and hits one side of a red hot valve stem, and it's all over.

I would get hold of a compression tester and get some readings. If you have really bad compression on one cylinder, and you have a way to pressurize it through the compression tester hose, you might be able to figure out where the leak is. In a quiet garage, bring the cyl up to TDC compression stroke, pump in a few psi of air, and listen at the oil fill, the throttle body, and the exhaust pipe for the sound of escaping air. Remember that the compression tester hose has a one-way check valve in it somewhere. You may have to remove it in order to pressurize the cylinder through that hose.

It is probably not a good idea to drive this car until you track down the problem. If it is one of the things it sounds like it is, driving it will only make things worse.

Is this engine stock? Some have suffered from cracked exhaust manifolds, but not bad enough to damage anything. Bent/burnt/broken exhaust valves don't often happen on stock 6 cyl BMWs, and cam problems are rare on stock engines with less than 200k miles, unless they are run low on oil.

Last edited by Manolito; 05-26-2008 at 06:17 PM.
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Old 05-26-2008, 09:41 PM
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the ticking noise can be only heard from under the car and at the exhaust pipe...the engine is stock..the exhaust is not cracked anywhere from what i can tell...why does it run rich then?
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Old 05-26-2008, 10:58 PM
 
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What is the symptom of rich running? Are those exhaust tips as black inside as they look in the video? If so, yup, its way rich.

A ticking sound under the car is usually an exhaust leak. You generally need to put it on ramps and run your hand along the pipe to find the leak. However, if you can't hear it in the engine compartment, then it is not right up at the exhaust port, so that leak can't have hurt an exhaust valve. Exhaust leaks down lower but ahead of the cat can confuse the oxygen sensors and can set a code, (and cause the engine to run rich as it tries to get rid of the excess oxygen that the second sensor is detecting) but do no real harm.

You see, with only three cylinders on a pipe, at idle, there is a distinct low pressure area between exhaust pulses, so a leak will leak both inward and outward at idle. The in-leak introduces oxygen to that exhaust, which the car interprets as very lean operation on three cylinders, and it tries to correct.

The noise I was hearing at the exhaust sounded a lot scarier then just a rich idle, but hope springs eternal.
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Old 05-26-2008, 11:04 PM
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when i say rich im talking eye watering rich...it has a strong smell to it. my buddy was riding behind me and he said its strong as hell and couldn't stand riding behind my car..the ticking noise is not really loud but is noticeable you cant hear it in the car but once outside you can hear it ..i opened the hood and listened around and could barely hear the ticking noise once i got my ear near the passenger side of the motor but when i get under the car it really sounds like a leak bu i cant find any leaks anywhere downstream but near the motor i cant get close enough because its hot..lol
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Old 05-27-2008, 08:56 AM
 
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Looking for a leak with your hand works best if you do it in the first few seconds after you start the car - unless you have asbestos hands ;-)

The rich smell could also be the result of running on 5 cyl and dumping the raw fuel from the 6th cyl back to the cat to be burned there. This can heat your cat up to red hot and destroy it.
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Old 05-27-2008, 06:52 PM
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Quote:
Originally Posted by Manolito View Post
Looking for a leak with your hand works best if you do it in the first few seconds after you start the car - unless you have asbestos hands ;-)

The rich smell could also be the result of running on 5 cyl and dumping the raw fuel from the 6th cyl back to the cat to be burned there. This can heat your cat up to red hot and destroy it.
if its running on 5 cyl then what would cause it? ive replaced the plugs and coil packs and hasn't changed anything
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Old 05-28-2008, 12:23 AM
 
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Next step is a compression test, and then a leak test on any cylinder with bad compression to see where the leak is.

Another way to see if you are running on 5 and find the culprit cylinder is to check the temperature of each exhaust pipe at the head. An infra-red non-contact thermometer is great for this job. I have to use my hand, so I have to do it in the first few seconds after the car starts.
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Old 05-29-2008, 05:36 PM
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Check the o2 sensor
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Old 05-29-2008, 10:45 PM
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alright i pulled off the muffler where it unbolts after the cats and you can hear the ticking sound alot better....here is a video of the noise...everyone says misfire but i replaced the plugs and coil packs to no avail...help please!
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Old 06-01-2008, 03:33 PM
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ok i pulled the valve cover and all the springs look good none collapsed or broken it also seems really clean in there and springs look newer...

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Old 06-01-2008, 05:33 PM
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upon futher inspection...everything is moving like it should from what i can tell so.....guess im going to be swapping motors...tired of it feeling like its running on 5 cylinders
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Old 06-02-2008, 10:57 AM
 
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Did you ever check compression?

If I were thinking of swapping motors, I would pull the head and have a look before going to all that work, and I would not pull the head unless the compression tester told me there was something fishy going on in one cylinder.
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Old 06-09-2008, 10:49 AM
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I've got a very similar situation - "puffy" exhaust sound, leaky exhaust smell, ticking sound, but add to it a lack of torque.

I noticed the ticking sound stopped when I stopped the physical movement of the exhaust by applying pressure to the tailpipe with my foot - so the ticking could be from added vibration?

Have you checked for holes in your exhaust system?
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