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Engine Knock with no CEL


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Ok I have a 2001 Boxster Base, 2.7L.

For week or two my car has made a slight rattling sound, but had no ryhme or reason. I thought maybe something was loose somewhere. Now it has turned into a full on knocking in what sounds like inside the engine. It is rpm dependent, but will sort of skip knocks too. Almost like if you put a marble in a dryer.

I have no CEL on, but I plugged in my sensor and came out with CEL P1411 P0410. The CEL light does come on in the light test during start up, so it looks to be working.

So my question is, is my engine about to be blown or is there someway one of these valves in the air injection system could be making such a loud knock. Is the knocking or this CEL unrelated? I see these CEL's are not uncommon, but I do not see anything that is accompanied by a knock.

Thanks for any information.

Tyler.

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I just had a similiar condition and really thought it was an internal knock. It turned out to be a water pump going bad.

I drove it for a few days after first noticing the sound. No CEL. Took it to a independant Porsche repair shop for

a diagnosis. The mechanic called, told me it was the pump. I drove it home and replaced the pump. The marbles in the dryer and knocking sound went away. I hope your problem is this easy. Good luck.

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The secondary air system codes could be unrelated. Unless perhaps the SAI pump has gone completely bad and is rattling around. However that would only happen on a cold start-up, and not be dependent on RPM.

I wouldn't drive the car without properly diagnosing this issue. Any sort of mechanical noises that sound like they are coming from inside the engine should be taken very seriously.

Have the car on a lift or ramp with a mechanics stethoscope ready to probe what area of the engine the noise is coming from. Only run the engine as long as necessary to diagnose where the noise is coming from.

If you are lucky, the noise will come from something that is external and easy to replace such as a bad spark plug, lose exhaust header, water pump, something caught in the accessory belt, or other accessory pulley problem.

Hope this helps and good luck.

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You could pull the serpentine belt off and run the car for a few seconds to see if the sound disappears. I guess that would only work if you can hear the knock at idle or revving while stopped. Or maybe pull the oil filter and look for metal. In fact, I think I'd do that first since it's so easy.

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Assuming the particles are ferro-magnetic and from your IMS bearing...

Best case you replace the IMS bearing with an LNE retrofit, install a magnetic drain plug or IMS Guardian, many oil changes, and be on your way.

Worst case, engine tear down to replace/repair broken parts & properly clean IMS debris.

There could be other reasons for small metal particles in the oil filter, it should be diagnosed properly.

Anyways, these are all all good reasons to not run the car until it gets sorted. Your car is worth a lot more with a running engine than without.

If you need it, someone was selling a 2.5 or 2.7 liter engine for $2500 on rennlist, granted it has a lot of miles but it runs and at a good price.

Best of luck.

Edited by logray
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If you have significant ferrous metal in your oil filter, either from the IMS or another source, just swapping out the IMS bearing is not a good idea as you need to get all of the debris out of the engine before it starts tearing up other things. Unfortunately, that means pulling the engine and disassembling it for a total clean out and rebuild, which should include the IMS update along with several other updated components. Just one piece of iron circulating with the oil can start a process leading to some serious heartache in these engines.

Some people have gotten away with pulling the sump cover and cleaning out all the crap when an IMS goes bad, but they tend to be the exception; the IMS retrofit was designed to be done before the bearing is toast, not after. I am also concerned about what you describe as a “knock”; typically an IMS makes a metallic rattling sound more akin to a coffee can full of bolts being shaken rather than a knocking sound; I think you may be facing a more serious issue like a rod bearing on the way out. If it is, and you updated the IMS, the rod would still fail anyway, and probably ruin the new IMS bearing as well in the process, even if it did not destroy the block, which is very common.

If your car was in my shop, I would check the camshaft deviation values at idle to see if they are stable an within spec; if they were, indicating the IMS was still good, I would recommend pulling the engine before the failing component turns the assembly into a boat anchor………

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Here's the link to that 2.5L engine for sale:

http://forums.rennlist.com/rennforums/boxster-and-boxster-s-986-forum/670319-boxster-2-5l-engine-for-sale-2500-obo.html

And if you want something really fun, swap in a 3.6L upgraded 3.4L 996 engine... a little more expensive of an endeavor mind you. :)

http://forums.rennlist.com/rennforums/8981023-post63.html

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Thanks for the information. I am not sure what I am going to do with it yet. I'd like to take it to a shop but the Army doesn't pay me enough to do that just yet. Just going to let it sit until I figure out what I am going to do with it. The idiot in me wants to take it to the auto shop on base and just start pulling things apart, but I need to take it to someone that knows that they are doing. I've had mixed luck in my auto endeavors and having never worked on a Porsche it would be a disaster.

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If you have significant ferrous metal in your oil filter, either from the IMS or another source, just swapping out the IMS bearing is not a good idea as you need to get all of the debris out of the engine before it starts tearing up other things. Unfortunately, that means pulling the engine and disassembling it for a total clean out and rebuild, which should include the IMS update along with several other updated components. Just one piece of iron circulating with the oil can start a process leading to some serious heartache in these engines.

Some people have gotten away with pulling the sump cover and cleaning out all the crap when an IMS goes bad, but they tend to be the exception; the IMS retrofit was designed to be done before the bearing is toast, not after. I am also concerned about what you describe as a “knock”; typically an IMS makes a metallic rattling sound more akin to a coffee can full of bolts being shaken rather than a knocking sound; I think you may be facing a more serious issue like a rod bearing on the way out. If it is, and you updated the IMS, the rod would still fail anyway, and probably ruin the new IMS bearing as well in the process, even if it did not destroy the block, which is very common.

If your car was in my shop, I would check the camshaft deviation values at idle to see if they are stable an within spec; if they were, indicating the IMS was still good, I would recommend pulling the engine before the failing component turns the assembly into a boat anchor………

At this point, though, would you actually start up the engine for further diagnosis? Seems risky.

Edited by blue2000s
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At this juncture, he has little to lose, but is considering spending a lot money to replace an IMS bearing that may not be bad or the source of the knock. The cam deviation values at idle only take a couple of seconds to acquire, and could totally eliminate the IMS as the source of the issue. If the deviation values are steady, it is time to shut it off and pull the engine...........

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At this juncture, he has little to lose, but is considering spending a lot money to replace an IMS bearing that may not be bad or the source of the knock. The cam deviation values at idle only take a couple of seconds to acquire, and could totally eliminate the IMS as the source of the issue. If the deviation values are steady, it is time to shut it off and pull the engine...........

How about pulling off the transmission and checking out the IMS support and maybe bearing before turning the engine back on. An hour or two of labor, right?

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