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Old 03-03-2017, 09:38 PM   #1
ryanr1299
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E46 2004 325i Misfire Under Heavy Acceleration [SOLVED]

*****
This issue has been solved. The problem was a clogged bank 2 catalytic converter. Both cats were replaced and the issue is gone. Read below for original problem.
*****

Hello all, hopefully I can get some insight from you all on where to go next with this. I've lurked here a long time, using this forum as a resource for engine issues on my E39 3.0L. I recently picked up an 04 325i with 210,000 miles on it for almost nothing and I'm having problems with misfires under heavy throttle. I feel like I've done the basics and my homework, but let me know what I've missed. This is LONG! Apologize in advance, but I want to get all the info out there, plus leave as much detail as possible for when this gets resolved and somebody else stumbles on the thread when they're having a similar problem.

History:
Bought the car two weeks ago, at the time it was running terribly with rough idle and misfires. It ran so poorly I did not even test drive it. The misfires were fixed with new plugs and coils, it would then rev nicely with no misfires (while parked), but the idle was horribly rough. Having gone through jfoj's thread on lean, idle, and misfires previously on my E39, I went through the same again and found the following:
** DISA broken (flap missing) -- replaced
** CCV broken -- replaced
** F-fitting vac lines (intake boot) falling apart -- replaced
** Intake boots surprisingly in good shape -- replaced anyway
** Throttle body cleaned, new gasket installed
** ICV cleaned
** Intake manifold gasket replaced
** Checked all remaining vac ports and lines on intake manifold while it was out -- all good

Note I removed the intake manifold after I found the DISA flap missing...scoped it, etc. but no sign of the flap.

After putting everything together, started it up and idle is smoothed out and steady, engine revs freely while parked, sounds good. Right away I had pending lean codes on both banks, however.

Took it for a drive and it was a bit sluggish but drove ok unless I gave it heavy throttle, then it would rev up to about 3-4k then beep and go into safe mode (traction, EML, and yellow brake lights on -- note the little gear icon did NOT appear), engine throttle was stuck around 1k, jumping back and forth +/- maybe 200 rpm...no response to gas pedal. Immediate shut down and restart and it was back to normal. There was no SES light with this, so I kept driving and reproducing it until it finally threw a P16A7. Apart from that, only the pending lean codes were there. Researching this I came across Baltimore Bimmer's diagnosis that landed finally on clogged cats. I also found on this forum and others the same issue and DTC...seemed like some people fixed it with new cats, others with new MAF. I tried to find a known good MAF to try before buying a new one, but couldn't find one. While doing that, and double checking everything under the hood (due to the lean codes) I didn't test drive the car for several days, now here we are...

Current status:
Car starts and idles great, with no SES light. When in park I can rev the engine easily to red line with no problems. All sounds good, very smooth. When driving the car feels generally sluggish but will drive ok unless I punch it and get the revs too high too fast. Then it sputters and holds the revs high without shifting up until I pull back on the throttle. After this it is misfiring and barely driveable. I can stop, shut it off, and restart and it's all back to normal and will run as before. I'm getting P0300 (random/multiple misfires) as well as P0304,0305,0306 for misfires on 4-5-6. Lean codes and P16A7 have not returned.


Data:
I've used the PDF of jfoj's logging/report to gather the following. I can get cold start up log tomorrow, highway log may not be feasible since car is not yet registered, etc. (just purchased). I'm new to the OBD stuff, so help interpreting these would be great. BTW ignore DTC for MAF ( MIL threw when I had started it at one point with the MAF unplugged...MIL is off now for this but code remains for now).
OBDFusion Diagnostics Report at Warm Idle
OBDFusion 4-Minute Log at Warm Idle

Last edited by ryanr1299; 03-22-2017 at 08:31 AM.
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Old 03-03-2017, 09:40 PM   #2
jfoj
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Quick reply.

Yes the P16A7 code is a tricky code, often means the converters may be a problem.

Overall the idle MAF values look in the proper range.

LTFT at idle are sky high, this car has Wideband O2 sensors which are usually pretty accurate and are tough to flag as lazy or in need of replacement.

The first thing I would do is verify 100% all the O2 sensor are connected to the proper engine bay connector. The lazy way to do this is just swap the Pre-cat O2 sensor connectors and see if the LTFT drops back toward the proper values.

The best way it to trace each O2 sensor wire from the sensor to the connector. Label each O2 sensor at the connector with the Bank and Sensor number such as B1S1. Then using OBDFusion, set up a dashboard with each O2 sensor. Then unplug a single sensor and see if what sensor Bank and Number quits responding and then verify it matches the label on the O2 sensor. If it is wrong the sensor wiring is swapped. Post-cat O2 sensors are also important on the newer cars with Wideband O2 sensors.

Fuel pump could also be a possible problem even though you checked it. The fuel pump volume is more important than the pressure. Fuel pumps soft fail and are consumable.

http://forum.e46fanatics.com/showthread.php?t=929501
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Fuel pump failures - http://forum.e46fanatics.com/showthread.php?t=929501

Temp Info - http://forum.e46fanatics.com/showthread.php?t=964491

Hidden OBC Menu - Check Voltage, Temp, Fuel Level - http://forum.e46fanatics.com/showthread.php?t=239619

E46/E39 GM5 Door Lock Info - www.bmwgm5.com

Lower hose temp switch O-ring - BMW #13621743299

Last edited by jfoj; 03-03-2017 at 09:42 PM.
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Old 03-03-2017, 10:55 PM   #3
ryanr1299
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jfoj,
Swapped the pre-cats and LTFT was still high. I only started it up and idled for a few minutes and monitored manually, but LTFT on both banks was up above 20. I can do the full tracing and testing tomorrow if it's still warranted after the swap test didn't show anything.

As for fuel pump -- Having read your thread on the fuel pumps when diagnosing issues with my E39, I'm aware of the soft failure modes but I'm curious if fuel pump would contribute to the high LTFT? Or are you mentioning it as a possible cause of the misfires independent of the LTFT?

Changing the pump and filter would be no problem. Do you think that's the next step?
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Old 03-03-2017, 11:35 PM   #4
jfoj
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Unless the car has the wrong DME flash, check the VIN number on the Diagnostic Report to the cars VIN and verify it is the correct engine code, the LTFT being so Lean will either be likely be a fuel volume, O2 sensor and/or MAF problem.

The MAF value at idle looks in the correct range, the O2 sensor appear to be working reasonably well, so this leaves either incorrectly connected O2 sensor connections or low fuel volume which could also cause misfires along with high LTFT's. The Bank #1 LTFT's typically could be higher/Leaner than Bank #2 due to the fuel line feeding from the rear of the fuel rail. But it looks like both the Banks are very Lean/high LTFT's.

Check the O2 sensor connections and report back.
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Fuel pump failures - http://forum.e46fanatics.com/showthread.php?t=929501

Temp Info - http://forum.e46fanatics.com/showthread.php?t=964491

Hidden OBC Menu - Check Voltage, Temp, Fuel Level - http://forum.e46fanatics.com/showthread.php?t=239619

E46/E39 GM5 Door Lock Info - www.bmwgm5.com

Lower hose temp switch O-ring - BMW #13621743299
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Old 03-04-2017, 11:40 AM   #5
ryanr1299
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Ok here we go. First some FYI info that got lost when I lost my original post, for anyone else reading. Initial diagnostics included fuel pressure check at idle and pressure hold after shut down, which gave me almost dead on 3.5bar with <0.5bar drop over 20 minutes after shut down. Also checked compression, which showed 195-178-190-191-175-190.

jfoj -
1. VIN on diagnostic report matches VIN on vehicle
2. Traced, disconnected, and measured all four O2 sensors -- they are connected correctly.
3. Overnight cold start up log for five minutes
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Old 03-04-2017, 03:19 PM   #6
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Not sure if this is useful but I thought I'd log one of the problematic test drives. I also did the same run in my E39 for general comparison...I know values will be different but I was interested in the relative patterns between the two cars (this exercise was mostly for my own learning). I noticed the air flow rate was much higher on the 2.5L E46 under hard throttle than on the 3.0L. I would have expected the opposite.

Full log file of test drive (gave it hard throttle starting about 151 seconds in)
Extracted some graphs -- may or may not be useful.
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Old 03-04-2017, 05:26 PM   #7
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I have not had a chance to look at the data, maybe later tonight?

You may want to pull one of the Pre-cat O2 sensors and drive the car and see how it runs, it will be noisy, but you should feel a difference if the exhaust is restricted.

You could also get an exhaust back pressure tester for a complete check as well - https://www.amazon.com/Tool-Aid-3360...ressure+tester

The Lean condition may be due to restricted exhaust and the inability for the the exhaust manifolds to clear out burned exhaust causing the O2 sensors to show a Lean conditions.
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Solve your misfires, lean codes, rough idle - http://forum.e46fanatics.com/showthread.php?t=897616

Fuel pump failures - http://forum.e46fanatics.com/showthread.php?t=929501

Temp Info - http://forum.e46fanatics.com/showthread.php?t=964491

Hidden OBC Menu - Check Voltage, Temp, Fuel Level - http://forum.e46fanatics.com/showthread.php?t=239619

E46/E39 GM5 Door Lock Info - www.bmwgm5.com

Lower hose temp switch O-ring - BMW #13621743299
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Old 03-04-2017, 10:20 PM   #8
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Thanks, would be interested in your take on the data. Not that I know much but what stood out to me is while LTFT is very high both banks, it dropped like a rock on bank 2 whenever I got into the throttle. Not sure what that means, though.

I'll probably get the exhaust pressure gauge to add to my collection here pretty soon...but how long is it ok to drive it with the O2 plugs out? It must throw a lot of heat into the engine bay and I could see it damaging something. It's about a 1/2 mile drive out of my neighborhood before I can really open the car up.

One other data point, I pulled the MAF out and looked it over real carefully. I found the plastic at the base of the element looks to be cracked. Here's the photo. Not sure if it's just a defect in the plastic or if it suggests a problem with the element itself.
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Old 03-05-2017, 01:33 PM   #9
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Ok, new day new data and I think we have a winner.

First, I managed to find a good MAF and swapped it in, no change. LTFT were maybe slightly lower on both banks but still really high, still drove the same...sluggish and misfired on 5 when I got into the throttle.

Popped the bank 2 pre-cat O2 out and drove it around the block. The engine came to life...sluggishness was pretty much gone and it would pull much harder and easier than before. So I think we're looking at clogged cats. I Amazon Prime'd the back pressure test kit which will be here tomorrow and I can get readings from both banks, but we may have found the answer.

Was hoping to save this E46 but with bad cats not sure it's feasible, seems they are very expensive to replace and this car needs other work even after the engine gets sorted out. I will update with pressure data when I have the kit.
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Old 03-05-2017, 02:08 PM   #10
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Yea, converters are expensive and if you have Emission Inspections this is not easy to work around.

Used converters are not to be sold by Federal Law as I recall, however, you might find someone on the forums or locally that is parting a car.

Or you might just by a wrecked parts car and get what you want and sell the rest!

Glad you are making some progress.

Good luck.
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Fuel pump failures - http://forum.e46fanatics.com/showthread.php?t=929501

Temp Info - http://forum.e46fanatics.com/showthread.php?t=964491

Hidden OBC Menu - Check Voltage, Temp, Fuel Level - http://forum.e46fanatics.com/showthread.php?t=239619

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Lower hose temp switch O-ring - BMW #13621743299
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Old 03-05-2017, 03:19 PM   #11
ryanr1299
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jfoj-
Many thanks for your help on this! If I had room for a parts car I'd do that in a heartbeat but it's just not practical for me. I'll update this thread one last time with exhaust back pressure data when I have it just to close the loop, but looks like I'll be selling or parting this one out.
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Old 03-06-2017, 06:49 PM   #12
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Measured back pressure on bank 2, pre-cat. The gauge was sputtering wildly between 1 and 3 PSI at idle, and went up quickly and held steady between 5-6 PSI when revved at 2500 rpm. Not sure what normal is but pretty sure it should be close to zero. At any rate, I think this confirms exhaust blockage, most likely cats. I'd need to measure post-cat to confirm it's the cats.

I did manage to score a pair of manifold assemblies from a wrecked E46 for pretty cheap with 130k miles on them. I'll have to finish testing bank 2 and check the other bank before proceeding but at least I have the parts I need.

One last question -- Are the blocked exhaust and the high fuel trim two separate problems or is the exhaust driving the high fuel trim? Put another way, if my cats are clogged and I replace them with good ones will the fuel trim come back to Earth or is that a separate problem I need to chase down?
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Old 03-06-2017, 06:59 PM   #13
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Yep, gauge should stay under 2 PSI as I recall, should not climb at fast idle, will really climb if you drive it and the converter is clogged.

Would not even test at Post-cat while a total PITA to get at, if the Pre-cats are restricted, the Post-cat measurements will will be next to no pressure.
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Solve your misfires, lean codes, rough idle - http://forum.e46fanatics.com/showthread.php?t=897616

Fuel pump failures - http://forum.e46fanatics.com/showthread.php?t=929501

Temp Info - http://forum.e46fanatics.com/showthread.php?t=964491

Hidden OBC Menu - Check Voltage, Temp, Fuel Level - http://forum.e46fanatics.com/showthread.php?t=239619

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Lower hose temp switch O-ring - BMW #13621743299

Last edited by jfoj; 03-06-2017 at 07:01 PM.
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Old 03-13-2017, 11:58 AM   #14
ryanr1299
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Quote:
Originally Posted by jfoj View Post
Yep, gauge should stay under 2 PSI as I recall, should not climb at fast idle, will really climb if you drive it and the converter is clogged.

Would not even test at Post-cat while a total PITA to get at, if the Pre-cats are restricted, the Post-cat measurements will will be next to no pressure.
So I haven't changed out the cats. Since I'm on a temp permit decided to see if I can drive it and get it ready for inspection instead. So it drives fine unless I go WOT. BTW everything has set to ready so far except EVAP and O2 heater.

Anyway I've put about 80 miles on it and the only code has been a bank 1 lean pending. Well it finally tripped the light this morning on my way to work. Freeze frame attached. I have the fuel pump ready to go in, since it's bank 1 only I'm guessing this is the most likely cause? Going to change it anyway but trying to isolate problems one at a time so I get a feel for everything rather than just throwing parts into it.

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Old 03-15-2017, 08:31 PM   #15
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Bump. New fuel pump and filter are in and the LTFT are running higher now than before on bank 1. I don't have a new set of logs but LTFT bank 1 is hanging around 30 +/- 3 at warm idle, with bank 2 around 20. Still only have one code - P0171. The engine never misfires...idles and runs great.

Could the clogged cats be driving the lean condition? Bank 2 cat is known to be at least partially clogged, never tested bank 1 pressure but under hard acceleration only bank 2 ever misfired, so thinking bank 1 is the healthier of the two if anything.

I'm pretty confident I don't have vac leaks given all the work I've done (and double checked). VCG is leaking quite badly, I have been putting off replacement to focus on the other issues...any possibility the leaking VCG could cause lean?
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Old 03-15-2017, 08:35 PM   #16
jfoj
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Post Freeze Frame data.

The problem is when the converters are clogged/restricted the cylinders cannot be purged of exhaust gases which are pretty much void of oxygen.

Then when the engine attempts to draw more air into the cylinders, there is a lack of free space for the new, fresh air and fuel to enter. So strange things happen.

But again, need to see some data to understand a bit better about what is going on.
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Solve your misfires, lean codes, rough idle - http://forum.e46fanatics.com/showthread.php?t=897616

Fuel pump failures - http://forum.e46fanatics.com/showthread.php?t=929501

Temp Info - http://forum.e46fanatics.com/showthread.php?t=964491

Hidden OBC Menu - Check Voltage, Temp, Fuel Level - http://forum.e46fanatics.com/showthread.php?t=239619

E46/E39 GM5 Door Lock Info - www.bmwgm5.com

Lower hose temp switch O-ring - BMW #13621743299
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Old 03-15-2017, 08:47 PM   #17
ryanr1299
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Quote:
Originally Posted by jfoj View Post
Post Freeze Frame data.

The problem is when the converters are clogged/restricted the cylinders cannot be purged of exhaust gases which are pretty much void of oxygen.

Then when the engine attempts to draw more air into the cylinders, there is a lack of free space for the new, fresh air and fuel to enter. So strange things happen.

But again, need to see some data to understand a bit better about what is going on.
Freeze Frame:



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Old 03-15-2017, 08:52 PM   #18
jfoj
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Quote:
Originally Posted by ryanr1299 View Post
Bump. New fuel pump and filter are in and the LTFT are running higher now than before on bank 1. I don't have a new set of logs but LTFT bank 1 is hanging around 30 +/- 3 at warm idle, with bank 2 around 20. Still only have one code - P0171. The engine never misfires...idles and runs great.
Are the above values accurate??

You are saying 20-30% LTFT's at idle??
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Solve your misfires, lean codes, rough idle - http://forum.e46fanatics.com/showthread.php?t=897616

Fuel pump failures - http://forum.e46fanatics.com/showthread.php?t=929501

Temp Info - http://forum.e46fanatics.com/showthread.php?t=964491

Hidden OBC Menu - Check Voltage, Temp, Fuel Level - http://forum.e46fanatics.com/showthread.php?t=239619

E46/E39 GM5 Door Lock Info - www.bmwgm5.com

Lower hose temp switch O-ring - BMW #13621743299
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Old 03-15-2017, 08:56 PM   #19
ryanr1299
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Quote:
Originally Posted by jfoj View Post
Are the above values accurate??

You are saying 20-30% LTFT's at idle??
Yeah. I could grab a warm idle log for you tonight if interested, since the car is warmed at the moment.

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Old 03-15-2017, 09:10 PM   #20
ryanr1299
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Quote:
Originally Posted by jfoj View Post
Are the above values accurate??

You are saying 20-30% LTFT's at idle??
It's accurate. Freeze frame is posted above also, FYI. Here's the warm idle log I just took:

Warm Idle
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