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Discussion Starter #1
I'm a new addition to BMW ownership after having acquired a 2001 320i a few weeks ago. I knew it had some problems when I bought it as I did an OBD scan, which showed a P0340. Did some research and decided it was easy enough to tackle. It is also in really, really good condition, has obviously been loved for most of it's life and was also really cheap (got it at an auction).

The car has practically no power. It is drivable, but the acceleration is terrible, especially on up-hills. You can feel some power come in from about 3k rpm, but the engine starts making a disturbing rattle the higher you go, more so when less power is being applied. It will also stall on take off if you just put your foot down, especially with the air con on.

The first thing I did was to order a replacement intake cam sensor. I installed it and cleared the code, but it returned instantly. Tried a couple of times to no avail.
At the same time, I got hold of a rebuilt VANOS to eliminate the possibility of the power problem being from that, as well as the engine rattle. I installed the rebuilt unit, and it has made a difference, but not much. The engine still rattles at high revs.

Next, I replaced the exhaust cam sensor, having read that sometimes you need to replace both. Still no change.

I then refurbished the DISA with one of those billet aluminium kits. This also showed a minor improvement, but still not anywhere near to where it should be.

I checked the intake system for vacuum leaks. Found a small leak in the upper CCV pipe where it goes into the rocker cover. Plugged it up with some silicon. There is also a minor leak somewhere under the intake manifold, but I can't tell exactly where.

I don't think the leak under the intake is significant enough to cause such drastic loss of power. Given that the P0340 code remains, I have to assume that the ECU is in limp mode, and that until I can resolve that, there is no point in spending a lot of effort on minor possibilities. I should also mention that no warning lights appear on the dash, so the OBD is all I have to go on.

I have read somewhere that sometimes you have to replace the crank angle sensor too. This does kind of make sense as the three sensors are somewhat related. I have ordered a replacement, but am I barking up the wrong tree? It is starting to get more expensive than I had hoped, as I also have to replace the upper coolant hose and will most likely have to replace the CCV pipes too, and who knows what else the future holds.

Don't get me wrong, it's a great car. really nice to drive and very comfortable. I'd just like it to work the way it's supposed to.

Any help or guidance would be appreciated.
 

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2003 330cic, 2003 325iT
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I think it is unlikely.

The problem is with the circuit, and presuming the sensors are not defective, the next step is to follow the wiring to th ECU and inspect for compromised pins, oil intrusion, or other obvious physical damage. It is not unheard of.

After that you should inspect the timing chain and tensioner. A loose chain can cause that code.
 

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What's mileage? MAF sensor could cause poor performance, and without error codes, as it still works but incorrectly. But before you replace anything else, check the condition of catalyzers. They could be completely clogged but yet not giving bad signal to post cat O sensors. Remove pre-cat O sensors and use endoscope.
 

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2004 330Ci 85k miles
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P0340 Camshaft Position Sensor Circuit Malfunction
https://www.obd-codes.com/p0340

I would check electrical continuity between each sensor's connector and their corresponding pins on the DME connectors in the e-box.

This video shows how to easily test a camshaft or crankshaft position sensor.

https://youtu.be/fTu5Lej-EUY
 

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Discussion Starter #7
I think it is unlikely.

The problem is with the circuit, and presuming the sensors are not defective, the next step is to follow the wiring to th ECU and inspect for compromised pins, oil intrusion, or other obvious physical damage. It is not unheard of.

After that you should inspect the timing chain and tensioner. A loose chain can cause that code.
Good point, that makes sense. I check and trace the wiring back to the ECU.

There is also a possibility of the timing chain tensioner being a problem. I understand that they are both sprung and hydraulic. If this is the case, I did find a fair amount of sludge around the cams when I took the rocker cover off, suggesting that it has either had infrequent oil changes and/or has ventilation problems. Either way, this does present the possibility that there may be blockages in the oil channels that feed the tensioner. I will be running a few engine flushes through over the next oil changes, which I am going to do every 300-400kms. Hopefully it will help, as I do not really want to have to remove and clean everything. I did inspect the chain when the VANOS was off though, and it seems pretty tight.
 

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Good point, that makes sense. I check and trace the wiring back to the ECU.

There is also a possibility of the timing chain tensioner being a problem. I understand that they are both sprung and hydraulic. If this is the case, I did find a fair amount of sludge around the cams when I took the rocker cover off, suggesting that it has either had infrequent oil changes and/or has ventilation problems. Either way, this does present the possibility that there may be blockages in the oil channels that feed the tensioner. I will be running a few engine flushes through over the next oil changes, which I am going to do every 300-400kms. Hopefully it will help, as I do not really want to have to remove and clean everything. I did inspect the chain when the VANOS was off though, and it seems pretty tight.
You don't seem to be concerned about your fuel/air mix. Probably the most common cause of poor performance. What are your fuel trims like?
 

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Discussion Starter #9
What's mileage? MAF sensor could cause poor performance, and without error codes, as it still works but incorrectly. But before you replace anything else, check the condition of catalyzers. They could be completely clogged but yet not giving bad signal to post cat O sensors. Remove pre-cat O sensors and use endoscope.
I completely forgot to mention the mileage. She's done 215,000kms (134,000miles).

I believe the MAF sensor is OK. How would I test it?

The catalyzers are an interesting thing though. I checked the voltages of all four O2 sensors while driving, and the pre-cat sensors seem to function as expected. The post-cat sensors though, show absolutely no movement. Both sit at a dead steady 0.44V, regardless of what the engine is doing. Here's a screenshot from Torque:


I'm fairly sure that the post-cat should show at least some variation.
 

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Discussion Starter #10
P0340 Camshaft Position Sensor Circuit Malfunction
https://www.obd-codes.com/p0340

I would check electrical continuity between each sensor's connector and their corresponding pins on the DME connectors in the e-box.

This video shows how to easily test a camshaft or crankshaft position sensor.

https://youtu.be/fTu5Lej-EUY
Thanks for that video. I'll check both the old and the new sensors when I get a chance.

I'll also trace the wiring back to the ECU and make sure the contacts are good and there is no resistance or shorts.
 

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2003 330cic, 2003 325iT
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At 134k you should have replaced the precat sensors by now if they are original. MAF is likely fine for 150-175k and is very hard to test.
 

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Discussion Starter #15
So, given that both post-cat oxygen sensors are not functional, I must assume that this is the primary cause of my problem. There are most likely other issues that are contributing to the problem, like vacuum leaks etc., but I don't think there is any point struggling with the little things until the obvious has been resolved.

Does anyone know if there is a supplier of the Bosch sensors in Australia that doesn't charge the earth? Or should I just get them from the US or UK?
 

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So, given that both post-cat oxygen sensors are not functional, I must assume that this is the primary cause of my problem. There are most likely other issues that are contributing to the problem, like vacuum leaks etc., but I don't think there is any point struggling with the little things until the obvious has been resolved.



Does anyone know if there is a supplier of the Bosch sensors in Australia that doesn't charge the earth? Or should I just get them from the US or UK?


Post-cut sensors have nothing to do with engine performance and all they do is monitoring work of cats. You can have catalyzers badly clogged but yet doing their job burning exhaust gases so no any codes will come from your post cat sensors.
Most mechanics underestimate condition of cats, and if no one point you on them doesn’t mean they are healthy. Driving with bad coil, as example, can melt your cat within couple of hundred km; bad valve stem seals load your cats with unburned oil- that’s how you get your cats clogged/ melted. Endoscope will
Clearly shows cats condition and that’s pretty much only way to check it, unless you get a manometer and see how bad gas flow is.
MAF diagnostic isn’t easy thing too, as it might show you reasonable numbers, and no codes, but if you you have a chance to get any working one to swap, you might find huge difference.
Pre-cat O-sensors is different story; yet they can last way more then 100k, so it there No codes from them they are probably not a problem.


Sent from my iPhone using E46Fanatics mobile app
 

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Discussion Starter #18
Thanks for your reply. I understand what you say about the cats being clogged, but I would think that it would represent a uniform reduction in performance through the rev range, probably more so in the higher ranges as the clogging would restrict the flow of exhaust gases. My problem is mostly on the lower rev range. When you first start the car in the morning, it will not accelerate at all past 8-12mph if you don't put your foot flat. It does this only for the first 30-60sec before improving, which it does over the next couple of minutes while the engine warms up.

However, even once the engine is at running temp, acceleration is woefully inadequate until you go past 3000rpm, especially if going uphill or if the aircon is on. There is just barely enough power to get you moving. It's for this reason that I think it's more likely to be related to fuel mixture and/or timing, but please feel free to correct me if I am misguided.
 

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Unplug the Maf and take it for a drive. If the MAF is good it should drive similar.
I get most of my parts from FCP euro. Great service and quality parts at reasonable prices.
Does the engine rattle sound metallic or plastic?
 

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To me it sounds like a wiring issue so checking the circuits from the camshaft position sensor to the ecm is what needs to happen. Also with the valve cover off you can pull/tug on the chain and any excessive slack will be noticeable. However you dont hear about failed chains/guides on these motors mainly because people overheat them and blow the headgasket first im guessing. As for your rattle have you tried unplugging your disa valve and going for a drive to see if the rattle is gone? This wont affect your code but may be the source of your rattle and is fairly commom failure.Typically they make noise over 2500 rpms. When you you unplug it the noise goes away most of the time. Also do you have long crank issues? A missing or intermitent cam signal will cause long cranks before starting
 
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