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Discussion Starter · #21 ·
Both banks are rich in both logs. The cruise total trims are worse than the hot idle total trims. Your problem is common to both banks.

I suspect that you have blocked Cat's

You MAF looks to be under reporting in the hot idle log. It is showing 2.5g/s when it should be around 3.0 g/s. An under reporting MAF causes Lean conditions, which you don't have. It might be a good MAF with the reading being a clue for your main problem.

Rich conditions are caused by:
  • Too much fuel. Too much fuel pressure. Not a common problem on the E46.
  • Not enough air. A really dirty air filter etc
  • A faulty sensor fooling the DME into thinking one of the above is happening when it's not. MAF and Pre-Cat O2 sensors. The MAF may be good, lets park that for a minute. The O2's look to be switching normally. The range is a little odd/small/reduced. What fuel are you using? It looks like an Ethanol blend? What % of Ethanol?
  • Blocked Cat's. You did not log the Post-Cat O2 sensors, so I can't see if your Cat's are the problem. Do you still have Cat's fitted?

The general symptoms of blocked Cat's are:
  • Under reporting MAF values
  • Fuel trims that get richer the more load/rpm's put on the engine.
  • Poor performance
  • Misfires

For Post- Cat O2 Sensors:
  • Cat's in good condition have Post-Cat O2 voltages above 0.5V when at steady highway cruise. There may be the odd momentary dips.
  • If O2 sensors are switching between 0.1 and 0.8V, then they are following the pre-cat O2 sensors (Cat’s not able to treat the exhaust) and indicates struggling Cat's. This is the same for either narrow band or wide band Pre-Cat O2 sensors. Expect to start seeing P0420 and P0430 codes.
  • If O2 sensors are flat lined somewhere below 0.5V, you have one of these problems:
    • Faulty post-cat sensors
    • Blocked Cats. Check fuel trims, they are likely double-digit rich at this time. Do a before the Cat’s exhaust pressure test.
    • Fuel mixture problems that are so lean that it is being reflected in the post-cat O2 sensor signals
unfortunately the motorway was closed (bloody roadworks) so I couldn't really get the cruse control on, I got stuck behind a truck doing 50mph but he kept slowing down - if you look towards the end of the log there is a bit around 50mph not sure if it is any help but I will try to get out tomorrow after work and record the 60mph cruse

one post cat o2 sensor was about 0.8v as you said the other was much lower about 0.3 - maybe that sensor is buggered ( do post cat sensors have any affect on fuel trims or just catalyst efficiency ? )
 

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2000 E46 323i, 3.0L, 2.8L and 2.0L Z3's
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Yes the bank 2 Post-Cat O2 sitting at 0.3V is not a good sign. Yes Post-Cat O2's fail.

Your rich conditions are on both banks, so it's something common to both banks. It's only bank 2 with a suspect Cat. Not sure if its the main problem.

The 2 sensors used in Fuel trim are the Pre-Cat O2 sensors and the MAF. We can check the MAF and its the more expensive of the sensors to replace. Run a Rev-Rise test and post a link to the CSV file. Not Datazap, as I have to load the file into a spread sheet and do some calculations.

Rev Rise Test
Run your normal OBD Fusion log. Hot engine and Cat’s, stationary car. The test is best done just after a drive. Slowly raise the rev's of the engine (gradual increase) up from idle to around 3,000 rpm. I mean slowly. It should take you 3-4 minutes to do this test.

It takes some skill to do this test due to the lightly loaded engine. A little throttle change results in a large rev change. Don’t run up and down the rev range getting used to the control. If you stuff up the first part of the test getting used to controlling the small rev changes, then redo the test.
 

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Discussion Starter · #23 ·
Yes the bank 2 Post-Cat O2 sitting at 0.3V is not a good sign. Yes Post-Cat O2's fail.

Your rich conditions are on both banks, so it's something common to both banks. It's only bank 2 with a suspect Cat. Not sure if its the main problem.

The 2 sensors used in Fuel trim are the Pre-Cat O2 sensors and the MAF. We can check the MAF and its the more expensive of the sensors to replace. Run a Rev-Rise test and post a link to the CSV file. Not Datazap, as I have to load the file into a spread sheet and do some calculations.

Rev Rise Test
Run your normal OBD Fusion log. Hot engine and Cat’s, stationary car. The test is best done just after a drive. Slowly raise the rev's of the engine (gradual increase) up from idle to around 3,000 rpm. I mean slowly. It should take you 3-4 minutes to do this test.

It takes some skill to do this test due to the lightly loaded engine. A little throttle change results in a large rev change. Don’t run up and down the rev range getting used to the control. If you stuff up the first part of the test getting used to controlling the small rev changes, then redo the test.
ill give it a go tonight,
how do I upload the.csv file wot accept it on here do you want me to email over to you ?
 

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2000 E46 323i, 3.0L, 2.8L and 2.0L Z3's
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how do I upload the.csv file
The usual way is to load the CSV file into DropBox which is a free file share service. You then post the link to the file in the forum post. You can do the same thing with your Google drive, if you have a Google account/Email address.
 

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Thank you for the logs. You did excellent work. They all showed the same thing.

Just one little tweak needed, Don't use 100ms for the sample rate in OBD Fusion. Set the logger trigger to "PID Frame". That way I don't get 58 lines of the same data to wade through.

All 3 logs showed the same thing.
  • Total Fuel Trims in the negative
  • MAF Error in the Positive
  • A steady calculated load but well below (about 1/2) what is expected.
As the trims are negative and the MAF Errors are positive, the MAF is not your problem. You can read more about this chart in: How to Make a MAF Model


Rectangle Slope Plot Font Line


I agree with @Sapote, your Bank 1 Cat is showing that it's blocked with a Post-Cat O2 sensor voltage of around 0.3V. Yet both banks total fuel trims are very close. Bank 1 Post-Cat Voltage is good, yet it's total fuel trim on both banks (and LTFT's) are negative.

Replacing Cat's are expensive.
  • Replace the Pre-Cat O2 sensors. They have a service life of 120,000 miles. See what happens to the Total Fuel trims.
  • Decide your end game, replace Cat's or go Cat-less Header and a tune to get rid of the trouble codes and warning lights through not having post-Cat O2sensors.
  • If you are going to replace the Cat's, then change the Post-Cat O2 sensors first. See what happens to the Post-Cat O2 Voltages. It might not be blocked cats and O2 sensors are a lot cheaper than new Cat's
 

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Don't use 100ms for the sample rate in OBD Fusion. Set the logger trigger to "PID Frame".
If trigger on PID frame instead of sampling time (I used 1sec), then the time axis is unknown and how do you make sense out of the the data graph? For example, STFT could look completely out of phase with O2 sensor voltage as these frames could be on different time stamp.
 

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Discussion Starter · #29 ·
Thank you for the logs. You did excellent work. They all showed the same thing.

Just one little tweak needed, Don't use 100ms for the sample rate in OBD Fusion. Set the logger trigger to "PID Frame". That way I don't get 58 lines of the same data to wade through.

All 3 logs showed the same thing.
  • Total Fuel Trims in the negative
  • MAF Error in the Positive
  • A steady calculated load but well below (about 1/2) what is expected.
As the trims are negative and the MAF Errors are positive, the MAF is not your problem. You can read more about this chart in: How to Make a MAF Model


View attachment 948314

I agree with @Sapote, your Bank 1 Cat is showing that it's blocked with a Post-Cat O2 sensor voltage of around 0.3V. Yet both banks total fuel trims are very close. Bank 1 Post-Cat Voltage is good, yet it's total fuel trim on both banks (and LTFT's) are negative.

Replacing Cat's are expensive.
  • Replace the Pre-Cat O2 sensors. They have a service life of 120,000 miles. See what happens to the Total Fuel trims.
  • Decide your end game, replace Cat's or go Cat-less Header and a tune to get rid of the trouble codes and warning lights through not having post-Cat O2sensors.
  • If you are going to replace the Cat's, then change the Post-Cat O2 sensors first. See what happens to the Post-Cat O2 Voltages. It might not be blocked cats and O2 sensors are a lot cheaper than new Cat's
I cant thank you and Sapote enough for your help,

I will order some new pre cat o2's and see what happens, worse case I guess ill go cat less headers and see if I can add a couple of sports cat downstream for emissions tests - in this case would it be worth trying to extend the post cat o2 sensor wiring and plug in after said sports cat ? (possibly where the 1st resonator/muffler is now just after the headers)
 

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If trigger on PID frame instead of sampling time (I used 1sec), then the time axis is unknown and how do you make sense out of the the data graph?
Sorry @Declamondo, I'm going to hijack your thread for a second.

I've switched to using PID Frame as the logging trigger some time back. There is a time stamp in the log file, so the data can be charted. The advantage is that sample time changes to match the amount of time it takes to capture the data (fill the frame) for the number of PID's being logged.

All Loggers that I've used (3 so far) have suffered from sample times that get slower the more PID's you log. This is because the logger has a list of PID's to collect and only updates the list when all PID information is collected. The "frame" is the container of PID information. More PID's to log = bigger frame = slower sample rate.

The advantage of using PID Frame is that you get the data as soon as it's available. It also removes the multiple lines of the same data.

Using a 1 second sample rate for our OBD Fusion logging gives between 5 to 7 lines of the same data until the frame is full and new data arrives.

I spreadsheet lots of logs, both my own and from forums like E46Fanatics. I don't always use the same PID list. PID Frame is good for me as I don't have to worry about changing the sample rate and don't have to see multiple lines of the same data. OBD Fusion and PID Frame has given me sample rates of between 2.6s to 5.1s. If I need to get quicker sample rates, I switch to TestO which can get down to 120ms.

More information can be found at: OCTech Support
 

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Discussion Starter · #32 ·
Can you just reuse the same cats but remove the inside gut? I guess the platinum honey comb can be broken with a poking rod to make a passage.
Building a honey comb is difficult but eating honey comb is easy, I think.
might be a good shout - I did have a look and there are not many headers to suit RHD cars, I'm going to change the o2 sensors first to be sure - else I will have emissions issues come Mot time
 

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Discussion Starter · #33 ·
Hi all,

O2 Sensors arrived today, will fit them later and update you all, in the meantime iv been thinking and wondered if the purge valve is related to the rich running ? ( not thinking this is the main cause and magical solution)
I did have P0444 code pop up multiple times for the pat few months while this issue is going but have ignored as I assume it wouldn't have caused a missfire
 

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Discussion Starter · #34 ·
changed pre cat sensors yesterday - reset adaptations - 60 mph cruse attached below - miss fire still apparent on cold starts and I am now starting to notice the odd hesitation/miss when going up hills
@NZ00Z3 would you mind having a look for me

 

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Had a quick look. This is the first set of logs with the Post-Cat O2 sensors. These are used to look at the operation of the CAT's.

This chart looks good except that the MAF level is just a spot low. It should be closer to 25 g/s.

Rectangle Slope Font Line Parallel


This chart show the engine is running rich.

Rectangle Slope Font Plot Parallel


This chart shows that the pre-cat O2's are good.
The blip at 419 seconds to fuel system status 4 lines up with a deceleration (sudden drop in rev's), so it's normal operation.

Azure Rectangle Slope Plot Font



This Chart shows That Bank 1 Cat is not too bad. It struggles a bit with changes in exhaust flow (MAF increases), but then settles down to a correct level.
Bank 2 CAT is blocked. The voltage sits around 0.39V all the time. It's not at 0.43V which would indicate a cold O2 sensors. So, It's looking like a blocked CAT.

Rectangle Slope Font Parallel Plot


Blocked Cat indicators are:
  • Rich fuel trims = check
  • MAF values that are lower than expected as the engine can't get rid of the exhaust gases, so there is less room to suck in new air. You Hot idle and Cruise MAF values are low = check
  • Post-Cat O2 signals that are either switching or flat lined under 0.5V = check.

The easy way to confirm is to remove the Pre-Cat O2 sensors from the exhaust and go for a drive to see if the performance is back. If it is, then the Blocked cats are confirmed. The car will be very Load, so watch out for cops.
 

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Discussion Starter · #39 ·
Thank you for running through that,
I do have a bank 2 sensor 2 code - but due to the fuel trims I take it the sensor could be bad but either way the cat is likely blocked and it wont matter either way if I did replace the sensor (righ now, obviously if I replaced the cat I would).
I have seen a company called bm catalysts over here who offer oem replacement for £350 ish. anyone ever used them ?
I was thinking I could sell the old cat to make the money back - this is my daily so not sure on going cat less

other option is could i not just weld in a sports cat a similar size to the original ? or will this cause a mine field of issues with fueling and the car getting confused

Thanks again for your help, this car is slowly making me hate it at the mo,
 
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