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BMW Z4 e85 3.0i
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Discussion Starter #1
Hello everyone. I just got a bmw z4 e85 3.0 (m54b30) with manual gearbox and 114000 km.
I know it’s different from e46, but the engine it’s well known in this forum.
The problem is that the car doesn't have the power it should have. Let me explain better, in the first gear up to the limiter, the car has a constant and not high power even after 4000/4500 rpm. Every now and then I feel that in this threshold there is a greater push. Furthermore, by sinking the gas pedal, the car makes more noise from the exhaust but without really pushing. I have connected the machine to inpa and the only codes I receive are on the o2 post cat sensor of the first bank, blocked at 0.42v, but I have read that the o2 post cat sensors do not affect the performance, and a code for the engine oil sensor . however, this also does not affect performance.
I checked the disa that I fixed, I checked for leaks from the suction circuit and there are none. I tested ccv and everything is ok.
I know it could be some of these VANOS, injectors, filter and fuel pump but having no codes I wouldn't want to change working parts. Any idea why I don't get more boost after 4500 rpm? Thanks

I forgot, I disconnected the maf and no change.
On the other hand, no problem at the minimum, nor an anomalous increase in the number of rpm
 

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BMW Z4 e85 3.0i
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Discussion Starter #3
Thanks for the reply. I’ve forgotten say that I try to run without both pre cat o2 sensor, but nothing change. Despite this test I’ve checked the cat with an endoscope and I took a picture. By seeing the photo I can notice a some line as if it were broken, but I’m not sure.
I can add two photos
 

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Thanks for the reply. I’ve forgotten say that I try to run without both pre cat o2 sensor, but nothing change. Despite this test I’ve checked the cat with an endoscope and I took a picture. By seeing the photo I can notice a some line as if it were broken, but I’m not sure.
I can add two photos
The thing is if the cat is blocked it doesn't matter what the o2 sensors say as there is still a physical blockage making a restriction in the exhaust which leads to power loss, it will be worth changing them anyway so you can pass an inspection/mot or decat if the tester is friendly enough

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BMW Z4 e85 3.0i
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Discussion Starter #6
The thing is if the cat is blocked it doesn't matter what the o2 sensors say as there is still a physical blockage making a restriction in the exhaust which leads to power loss, it will be worth changing them anyway so you can pass an inspection/mot or decat if the tester is friendly enough

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I apologize maybe I was not very specific. By removing the sensors 02, I mean physically removed from the holes, leaving them open to restore any pressure, by means of the escape of the exhaust gases from these.
 

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The thing is if the cat is blocked it doesn't matter what the o2 sensors say as there is still a physical blockage making a restriction in the exhaust which leads to power loss, it will be worth changing them anyway so you can pass an inspection/mot or decat if the tester is friendly enough

Sent from my SM-G973F using Tapatalk
But removing O2's on an exhaust with blocked cats should make the car run better because the backpressure would release through O2 openings. Fixed 0.42V on downstream O2 is a default value. Meaning it either is missing/disconnected or can't reacch operating temperature. I guess clogged cat might cause it not to to heat up. The definitive test for clogged cats is to remove front O2 sensor and install pressure gauge in it's place. The pressure measured should be almost none.
 

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2003 325i (M54B30 swap)
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Couple of things come to mind.

Sounds like it’s not cats. I’d look at all your sensors and see if their values look about right. VANOS could be knackered but my personal guess is low compression losing power. How long ago did you buy it, and did you have it compression tested?
 

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But removing O2's on an exhaust with blocked cats should make the car run better because the backpressure would release through O2 openings. Fixed 0.42V on downstream O2 is a default value. Meaning it either is missing/disconnected or can't reacch operating temperature. I guess clogged cat might cause it not to to heat up. The definitive test for clogged cats is to remove front O2 sensor and install pressure gauge in it's place. The pressure measured should be almost none.
I was able to diagnose my clogged cats In 2018 by doing exactly this. Removed pre cat o2s and drove and the car was perfect, albeit loud as no other

I also put a pressure gauge on her and at 0-2000 rpm the back pressure was null. It was only until I revved her past that I'd get blips of 6+ psi back pressure. Hence my limp mode at random times at mid to high rpms. Also, if she's chugging oil the cats being affected are likely. My car was eating a quart every 700-800 miles. I then said f off to the factory ccv system and went with the Bavarian mod. I now consume a quart every 4-500 miles depending on how liberal I've been driving her.

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But removing O2's on an exhaust with blocked cats should make the car run better because the backpressure would release through O2 openings. Fixed 0.42V on downstream O2 is a default value. Meaning it either is missing/disconnected or can't reacch operating temperature. I guess clogged cat might cause it not to to heat up. The definitive test for clogged cats is to remove front O2 sensor and install pressure gauge in it's place. The pressure measured should be almost none.
Yeah i thought he meant he had just disconnected the connectors to the sensors but he has confirmed that he completely removed them, i cant imagine it would be the vanos as that generally affects the low rpm range most and also would throw a code if it were that bad due to the target position and the actual would be so fat apart, I would say test compression and go from there

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BMW Z4 e85 3.0i
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Discussion Starter #12
What’s the fuel pressure?
Post all the trouble codes.
These are the codes:
- p0140 (o2 sensor post cats)
-p2271 (o2 sensor post cats)
-27C3 (thermal oil sensor)
The fuel pressure was measured by inpa (not directly on the injector track) and its value is 450 kPa = 4.5 bar
 

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BMW Z4 e85 3.0i
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Discussion Starter #13
But removing O2's on an exhaust with blocked cats should make the car run better because the backpressure would release through O2 openings. Fixed 0.42V on downstream O2 is a default value. Meaning it either is missing/disconnected or can't reacch operating temperature. I guess clogged cat might cause it not to to heat up. The definitive test for clogged cats is to remove front O2 sensor and install pressure gauge in it's place. The pressure measured should be almost none.
This what exactly I think
 

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BMW Z4 e85 3.0i
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Discussion Starter #14
I've bought the car one month ago and I haven't done the compression test.
I also knew that VANOS had to do with low revs, so I ruled it out.
I've checked the car with INPA, I can post the results if it could be useful, but I don't see nothing strange.
I can feel the power of the car if I position myself between 3500 4500 rpm, pressing the gas pedal a little, but if I push it completely, the power is less even if the revs go up normally

Thanks everyone for the help. I'll try to find a way to do the compression test.
 

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BMW Z4 e85 3.0i
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Discussion Starter #15
I forgot, I have traveled 2400 miles (2000 km) and it doesn't seem to consume oil
 

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2000 E46 323i, 3.0L and 2.0L Z3's
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Check your DISA valve.

I worked on a 323Ci manual transmission that would not rev over 4,000 rpm in any gear. The DISA valve failed inspection and was replaced. Problem solved.
 

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BMW Z4 e85 3.0i
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Discussion Starter #18
Check your DISA valve.

I worked on a 323Ci manual transmission that would not rev over 4,000 rpm in any gear. The DISA valve failed inspection and was replaced. Problem solved.
I have already inspected the disa, it was broken before but I fixed it. Now he makes the right resistance and holds the void. But I was wondering if it was possible that the disa really opened after 4000 rpm, is there a way to see?
 

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Discussion Starter #20 (Edited)
Today I did a test, I connected the endoscope to the arm of the disa to see when it would open. I have found that it opens close to 5000rpm sometimes (4500/4800 I think), isn't it pretty late? Sometimes it opened much earlier, around 2500. Sometimes it closed and opened very quickly after 5000 rpm, and this is strange.
Anyone know anything?
Thank you

I have documented this should be the correct functioning of the disa, more difficult than simply opening and closing at a specific number of rpm.
 
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