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Discussion Starter #1
I recently scored a deal for 2 e46 325xi's. One is a wagon, one a sedan. They both have misfires, the sedan is cyl. 2 and the wagon is cyl. 5, they both knock, the wagon harder than the sedan. Previous owner says that the problem with the sedan is there is a ton of carbon buildup on the exhaust valves in cyl. 2 because he was running bad cats for a while and there was a lot of heat. He says the problem with the wagon is a compression or oil ring. I want the sedan to be my daily, so repairing that takes priority and I can pull parts from the wagon if need be.

I have 2 ideas- put the entire cylinder head from the wagon on the sedan, or take the cylinder head out of the sedan, have the valves redone and possibly having the head resurfaced. I am relatively new to the car scene, and these are my first BMW's, after wanting them since I turned 15. If anyone could offer some advice as to what the possible problems could be, or how to repair them, it would be greatly appreciated.
 

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That's.........certainly an option. And a metric shit ton of work without ever identifying a root cause.

This post here is a great place to start. Most of the common misfires can be fixed by following this post. It's easy once you follow and read up on these cars, but it will take you time. Compared to pulling heads this is a much more simple entry point to E46 maintenance.

 

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Discussion Starter #3
That's.........certainly an option. And a metric shit ton of work without ever identifying a root cause.

This post here is a great place to start. Most of the common misfires can be fixed by following this post. It's easy once you follow and read up on these cars, but it will take you time. Compared to pulling heads this is a much more simple entry point to E46 maintenance.

Very helpful. Thank you!
 

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First off I would ignore most of what the seller says...

Unless there is zero compression in a cylinder, I think you can get both cars going without extreme measures like a head gasket... And a head gasket is an extreme measure.

Since you are a newbie wrencher and new to BMWs. You can't learn enough. you will need to spend at least twice as much time researching than you will actually turning a wrench.

In addition to following the thread above, you should get a BMW-specific code reader - not a generic OBD2 reader. Foxwell and Creator are popular - look them up. Do either of these cars have codes currently.

If time is important, I would find a non-dealer BMW Specialist in your area and go make friends with him. Pay him to get the sedan on the road. The wagon, unless it is a complete beater, is likely quite valuable. You can take your time bringing that back.
 

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Discussion Starter #7
First off I would ignore most of what the seller says...

Unless there is zero compression in a cylinder, I think you can get both cars going without extreme measures like a head gasket... And a head gasket is an extreme measure.

Since you are a newbie wrencher and new to BMWs. You can't learn enough. you will need to spend at least twice as much time researching than you will actually turning a wrench.

In addition to following the thread above, you should get a BMW-specific code reader - not a generic OBD2 reader. Foxwell and Creator are popular - look them up. Do either of these cars have codes currently.

If time is important, I would find a non-dealer BMW Specialist in your area and go make friends with him. Pay him to get the sedan on the road. The wagon, unless it is a complete beater, is likely quite valuable. You can take your time bringing that back.
They both have codes, the wagon cylinder 2 misfire and wagon cylinder 5 misfire
 

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If you dont know much about these cars if i were you i would take the car to a bmw specialist to have it diagnose it that would cost you about 150 but you will know what the problem is and then i would look up diy videos on youtube and save money on labor and put that money into better parts and tools that you would need
 

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Discussion Starter #11
Also do the cars have misfires all the time? Or only when cold warm or hot?
Both at lower RPMs. I have a few friends that are mechanics and they’ve all told me that the knock at lower RPM is a valve problem. I also have a report from the previous owners mechanic where he put a camera down the cylinder and saw the blocked valve
 

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You've certainly got your work cut out for you. You only want to do the job once, so of utmost importance is being Sherlock Holmes and finding out (for sure, NOT a guess) what the issues are and what the corrective measures will be for both. (Remember, the 3 "C's", complaint, cause, correction. With a heavy emphasis on the later two.)
When you know what's wrong with each and what will correct the issue(s) you can create a strategy and move forward intelligently from there. Be it a cylinder head swap or whatever.

If the PO's shop diagnosis is correct(?) of carbon buildup on the valve, you have two things to think about on that one:
If the valve is hung open by the carbon, did it at anytime hit the piston?
A valve job in in the offing for that one. Which might be the best thing overall, depending on what you find about the above.

Now just because you have a duplicate of used parts available (2 cars) it does not mean that all of the used parts are serviceable. Do some detective work, evaluate what the end product will be and what parts/time/labor (yours and/or some outside) will be needed to bring this to fruition.

It all can be done, however I can't stress enough the importance of knowing what's wrong, what's the corrective measures and what's the plan. Doing so beforehand will be more satisfying in the end and will help negate getting 95% done only to chase your tail with weird running issues after you fire it up.
Keep us in the loop.
Good luck.
 

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Discussion Starter #13
You've certainly got your work cut out for you. You only want to do the job once, so of utmost importance is being Sherlock Holmes and finding out (for sure, NOT a guess) what the issues are and what the corrective measures will be for both. (Remember, the 3 "C's", complaint, cause, correction. With a heavy emphasis on the later two.)
When you know what's wrong with each and what will correct the issue(s) you can create a strategy and move forward intelligently from there. Be it a cylinder head swap or whatever.

If the PO's shop diagnosis is correct(?) of carbon buildup on the valve, you have two things to think about on that one:
If the valve is hung open by the carbon, did it at anytime hit the piston?
A valve job in in the offing for that one. Which might be the best thing overall, depending on what you find about the above.

Now just because you have a duplicate of used parts available (2 cars) it does not mean that all of the used parts are serviceable. Do some detective work, evaluate what the end product will be and what parts/time/labor (yours and/or some outside) will be needed to bring this to fruition.

It all can be done, however I can't stress enough the importance of knowing what's wrong, what's the corrective measures and what's the plan. Doing so beforehand will be more satisfying in the end and will help negate getting 95% done only to chase your tail with weird running issues after you fire it up.
Keep us in the loop.
Good luck.
I am getting it looked at by a mechanic tomorrow. If the valve were to hit the piston, what would I be in for?
 

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Discussion Starter #14
I recently scored a deal for 2 e46 325xi's. One is a wagon, one a sedan. They both have misfires, the sedan is cyl. 2 and the wagon is cyl. 5, they both knock, the wagon harder than the sedan. Previous owner says that the problem with the sedan is there is a ton of carbon buildup on the exhaust valves in cyl. 2 because he was running bad cats for a while and there was a lot of heat. He says the problem with the wagon is a compression or oil ring. I want the sedan to be my daily, so repairing that takes priority and I can pull parts from the wagon if need be.

I have 2 ideas- put the entire cylinder head from the wagon on the sedan, or take the cylinder head out of the sedan, have the valves redone and possibly having the head resurfaced. I am relatively new to the car scene, and these are my first BMW's, after wanting them since I turned 15. If anyone could offer some advice as to what the possible problems could be, or how to repair them, it would be greatly appreciated.
UPDATE- I got the mechanic to look into the sedan a bit today. We did a leak down test, cyl. 1 and 3 have perfect compression but cyl. 2 is losing 35%. The fact that the surrounding cylinders have good compression takes away my worry about a bad head gasket or warped head. We swapped plugs and coils from cylinders 1 to 2 and the problem stayed on 2, so we know its not plugs or coils. He then did a test where he listened to the injectors when the engine was idling and did not hear anything from cyl 2, so he thinks it has something to do with the injector or something else fuel related. We are planning on going into more depth later this week when he can get his laptop with BMW scanning software, but I am relieved that I will probably not have to pull the head out.
 

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Clear the faults and redouble your diagnostics. OBD 2 will shut off any injector for a cylinder so it doesn't pollute.
You need make sure the reason it's off is because of a shut off by the DME or the injector itself and/or the wiring.

Keep in mind that part 3 of the swap routine is swapping injectors.
 

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Discussion Starter #16
Clear the faults and redouble your diagnostics. OBD 2 will shut off any injector for a cylinder so it doesn't pollute.
You need make sure the reason it's off is because of a shut off by the DME or the injector itself and/or the wiring.

Keep in mind that part 3 of the swap routine is swapping injectors.
Wiring is good. We checked everything. PO said that the cylinder was shut off so it didn’t pollute, like you said
 

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There's an old saying, trust but verify.
 

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Discussion Starter #18
A scanner will verify that, correct? My mechanic has BMW scanning software on his laptop he’s supposed to bring over this week
 

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Discussion Starter #19
UPDATE
The problem is in fact a bad valve. Took the head off and theres a nice chunk missing from an exhaust valve. Thankfully I have a friend who will do the job for me for only $75. I am replacing head gasket, head bolts, camshaft and crankshaft sensors as well as plugs and coils while I have everything apart.
 

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That is a lot of work for $75. You have a very good friend. It doesn't sound like you know if there were ever overheating issues with this car, but you do not want your buddy to do this much work and then you fail torque tightening. You should really pre-emptively do the Timeserts on the block. Additionally, with the head off you should pressure test it and check for flatness. Since you already have the cam's off that's a relatively cheap job to get done and is worth knowing what you're starting with. You also have access to cooling components you normally wouldn't get to, go ahead and replace it all right now.

And I guess I'll go ahead and be the negative Nancy here, but I don't think you really have to replace coils as PM. They're expensive and if you don't know they're bad then that's bad money (in my opinion) to put into the car. Just my $.02.
 
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