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Discussion Starter · #1 · (Edited)
Hello and happy Sunday everyone. I am in need of your help with a current issue I’m dealing with.

I had the car in storage for about a year and a half while I was in service, came back to find failed electric fan but also have codes.

The car sure feels like it’s having lots of fuel dumped causing lazy acceleration and horrible fuel mileage 13 city 20 highway if I baby the car! That is about 5mpg less of both from before. I have this car for last 13 years so I am very familiar with how it should run. I also have a 2002 540 which normally runs almost identical mpg. Driving around with sunroof open pulled all the stench inside giving me a headache.
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The car has brand new mafs from the dealer, all new CSPS intake and exh, new TS, new fuel pump - fuel filter - fpr. I also changed o2 sensors and plugs. I have new 200 cell cats and evolve headers.

The car was an animal before where it would loose traction just going WOT 2nd gear clutch engaged. The low end TQ is also gone and the car feels more like my 540, I would say 50hp more.We placed it on the dyno and it put down 354 whp ( 353 it was stock same dyno )
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All the hoses under plenum have been changed and the car was smoked twice with no visible leaks.
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I have read countless posts ( some seriously frustrating, and confusing )
here are some shots from INPA.
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Thank you for any and all help. I throw in the towel as I reach the end of my ability to diagnose.
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I also have a video from INPA if needed -
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When did you last clear the codes? Is the check engine light on? How long have all those new parts been on the car? If you have not cleared the codes in sometime, clear them and see what comes back, always the first step.
Sort of sounds like an exhaust leak before the O2s but I don't see the codes I would expect and all those other codes are confusing to say the least. Since the car has been parked and is likely cold go out with your volt meter and take a reading of the battery voltage right at the battery. If it is less than 12.7 put a charger on it over night at 5 amps if you can and read the volts when you first disconnect the charger. Then draw some power for a few mins, head lights or interior fan at high but don't start the car. Now read that voltage at the battery. Then just to be sure after you have all that done start the car and put your meter on AC volts and read the battery again, start at the highest scale of the meter and work your way down don't go lower if you get a reading.
 

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I had a similar experience with my e36 M3, after sitting in storage for a long time it ran rich and blew clouds. After replacing everything else I popped another good used ECU in it and all of a sudden it straightened out. Probably component failure or a cold solder joint.


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Subd. I have similar issue with rich condition, loss of low end, and smoke. Changed MAF's with no avail. I literally replaced everything on the car within the last 2 years besides the correlation sensors. Everything besides head gaskets and piston rings lol
might do a leakdown test sometime soon..
 

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Discussion Starter · #5 ·
When did you last clear the codes? Is the check engine light on? How long have all those new parts been on the car? If you have not cleared the codes in sometime, clear them and see what comes back, always the first step.
Sort of sounds like an exhaust leak before the O2s but I don't see the codes I would expect and all those other codes are confusing to say the least. Since the car has been parked and is likely cold go out with your volt meter and take a reading of the battery voltage right at the battery. If it is less than 12.7 put a charger on it over night at 5 amps if you can and read the volts when you first disconnect the charger. Then draw some power for a few mins, head lights or interior fan at high but don't start the car. Now read that voltage at the battery. Then just to be sure after you have all that done start the car and put your meter on AC volts and read the battery again, start at the highest scale of the meter and work your way down don't go lower if you get a reading.
All the parts were replaced before I left by a reputable shop. Car is sitting on new battery and trickle charger, voltage is good.

No check engine light, codes haven’t been cleared in over a year, so I just cleared them last night and replaced failing fuel sender unit. ( tech at Bmw dealer said it affects the performance and fuel ratios 🤷‍♂️)

I drove the car car and it doesn’t stink anymore ( my dad would start the car and take it for short drives occasionally for me )

I will put few hundred miles on and see what happens. On a short drive around down I’m getting 17-18mpg, so let’s see what happens. If it’s a leak the adaptations should change and the car will stink again, it also feels stronger, I don’t know if there is any relation to the issue.

btw, who do you recommend to tune for headers and 200cel cats?

Thank you 🙏
 

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Discussion Starter · #6 ·
After 15 miles or so driving they are adapting. I did smoke check to check for leaks and didn’t find anything. Let me drive some more and recheck the adaptations. If memory serves me right, my adaptations always stayed close to 0
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No check engine light, codes
That is a pretty big indicator the codes are old and not active. Some of those could have been triggered when the parts were getting installed if the key was cycled. Just have to wait and see what comes back. With that big list of codes that don't really appear related you would normally think electrical problem.
In the Audi forums we have seen in the past year a significant number of new batteries that seem to be strong only have a charged voltage of <12V. No explanation seems very strange, all I can say is it seems to be with glass mat batteries and it plays havoc with the computers. Likely some strange manufacturing error. The other thing short of a bad computer that does that is stray AC volts from a single failed diode in the ALT, I would encourage you to do the AC volt test.
You do have one serious code there and it is the empty tank code, and is caused by the car running super rich and symptoms do say that is likely. Most often that can be an exhaust leak which is really an air leak getting into the pipes and being read by the O2s. Exhaust system pulse and on the low side can suck air in. It can be many things inspection and pressure testing the exhaust system are the only way to find them.
 

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Discussion Starter · #8 ·
That is a pretty big indicator the codes are old and not active. Some of those could have been triggered when the parts were getting installed if the key was cycled. Just have to wait and see what comes back. With that big list of codes that don't really appear related you would normally think electrical problem.
In the Audi forums we have seen in the past year a significant number of new batteries that seem to be strong only have a charged voltage of <12V. No explanation seems very strange, all I can say is it seems to be with glass mat batteries and it plays havoc with the computers. Likely some strange manufacturing error. The other thing short of a bad computer that does that is stray AC volts from a single failed diode in the ALT, I would encourage you to do the AC volt test.
You do have one serious code there and it is the empty tank code, and is caused by the car running super rich and symptoms do say that is likely. Most often that can be an exhaust leak which is really an air leak getting into the pipes and being read by the O2s. Exhaust system pulse and on the low side can suck air in. It can be many things inspection and pressure testing the exhaust system are the only way to find them.
I checked the battery and its 13.7v and the alternator was replaced about two years ago with unit from Clemster. How would I check any exhaust leaks? The car is missing that sharp strong exhaust note I am accustomed to.

The car ran so rich I couldn't even drive with roof open because it would suck all the fumes in. hmmm..... Iw ill give some time to adopt and see what happens, but the Exhaust was custom fabricated by a good shop that builds motors and all for BMW's.

Anyone you recommend for tune?

Thank you, this forum is the best.
 

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Discussion Starter · #9 · (Edited)
I found this in SEARCH. I didnt think of this as my rear bumper was painted and carbon diffuser installed. This is right before I drove the car last time. My dad actually picked up the car for me.

"code 149 fault with empty tank / error if tank is empty"

I also had body shop work on the car rear!!! It all points to lean condition.

How can I check proper 02s readings without going to a shop for test?
 

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It all points to lean condition.
That thread does not say the car is lean it says the car thinks it is lean, but has cranked up the fuel to max rich. When the code is triggered the O2s report a super lean condition but that can be because the car can't supply enough fuel at that moment or air is getting to the O2 so it thinks it is lean.
Testing for leaks is simple for me but I built a system. I have 4 caps that fit on the tail pipes tightly and are clamped. Then I have 2 plywood pieces that are weather striped to replace the air filters. Then I pull the dipstick and put on a fitting I made that allows me to connect to a compressor set at 2 - 5 psi depends and I apply some air. Then listen for leaks. You could simply put the car up and start it and listen close for leaks, although small leaks at a bung or joint might not be heard. It you smoke the area you would still see air movement in the smoke.
 

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Discussion Starter · #12 ·
That is not right unless you had the charger on it when you read the volts. It can read high if you don'r take the surface charge off IE lights on or fan run for a minute or two.
I will recheck
 

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I will recheck
Let me give you a battery chart, this according to BMW, that said I have not seen many a battery that can really hold +12.9 V 12.8 yes most I have come across might do 12.85 but only on Wed between 4 and 6 in the afternoon,LOL. 12.75 V is what most report because these cars are constantly consuming power to sit still.
 

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Discussion Starter · #14 ·
That is not right unless you had the charger on it when you read the volts. It can read high if you don'r take the surface charge off IE lights on or fan run for a minute or two.
I apologize, I think I read it from OBC WHI
Let me give you a battery chart, this according to BMW, that said I have not seen many a battery that can really hold +12.9 V 12.8 yes most I have come across might do 12.85 but only on Wed between 4 and 6 in the afternoon,LOL. 12.75 V is what most report because these cars are constantly consuming power to sit still.
The battery is at 12.8v. I checked again without having trickle charger hooked up, DUH
 

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Discussion Starter · #15 ·
Do you think there is anything I should check that the body shop did while working on the rear end? They removed the bumper and all. Could there be air coming in somewhere there? My Headers ( evolve ) before the issue started so I am eliminating possibility of air getting in that way. Worth checking however.
 

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Do you think there is anything I should check that the body shop did while working on the rear end?
I can't see anything there. Maybe depending on the diffuser that could be messing with the proper airflow around the car and that is why you smell it with the sunroof open. The smell should not be there and that is from too rich and the cats can't process the poor mix. Diffuser or even front splitters are not going to do anything good on an M5 unless you drop them down 3 or 4 inches. They look cool, and not doing anything too bad so there is a win there.
 

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Discussion Starter · #17 ·
I can't see anything there. Maybe depending on the diffuser that could be messing with the proper airflow around the car and that is why you smell it with the sunroof open. The smell should not be there and that is from too rich and the cats can't process the poor mix. Diffuser or even front splitters are not going to do anything good on an M5 unless you drop them down 3 or 4 inches. They look cool, and not doing anything too bad so there is a win there.
I checked the voltage of the car standing and adaptations again after rested and driving around. This is a shot of the car with ignition in pos 2 to check for codes ( 0 codes ) but it's obviously running rich. I wonder what else I could check beside exhaust which was already smoked.

thank you again.
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Here are the screen shots.

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Kinda brings back memories of when I first picked up my car from the PO. It was down about 100hp or so - I'd say 540 levels.
In my case it was clearly evident from the MAF tests - I would get around 95L/hr fuel - that's it.
Did all the usual suspects, Plugs, MAFS, etc.
When I replaced the leading O2's I got an O2 warning.
Had run out of resources and decided taking it to the $tealership was the only option. Had a master tech look at it. Found an exhaust leak right at the leading O2 sensor bung.
Likely this was drawing in outside air and the O2 was thinking it was a super lean condition - so more fuel was required.

Let me say - that fixing that leak - rid the M5 of the 540 power. MAF test confirmed ~140L/hr.
Now if I ever have the car at a shop and I suspect it's down on power - I ask them to check for exhaust leaks.

But the first scans you posted had a lot of errors 0010 - Short Circuit to Ground or Value Too Small.
But then there is a 13.7V registered as the voltage.

From the S52 Engine Electronics Manual
MSS52 control module calculates the correct injection time based on the control parameters of:

• Engine speed
• Air mass
• Throttle position
• Oxygen Sensor feedback signal
• Engine coolant
• Barometric pressure
• Battery voltage
• Catalyst Temperature Sensor

The injectors receive operating power from the main relay and the control module provides the ground for the duration of the injection time (MS value).

If you have a grounding issue in the ECM - then that might be the reason for all your issues.
Wouldn't be a bad idea to check on the grounding points to see if they are free of corrosion.
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Main Relay Control
The MS S52 control module activates the main relay when KL 15 is switched ON. This provides
operating power for the control module and in addition the following systems/circuits
also receive operating power from the main relay:
• Traction control module
• Fuel pump relay
• Secondary air pump relay/air pump
• E-box cooling fan
• Auxiliary oil pump solenoids
• Purge valve
• Fuel injectors
• Vanos solenoids
• Oxygen sensor heaters
• Air mass sensors
• Idle control valve
The MS S52 maintains the ground for the main relay for a short duration after the ignition
has been switched off. This allows the control module to store the adaption values and any
fault codes.

Good luck exorcising those demons.
 

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I could check beside exhaust which was already smoked.
Don't know what to tell you, I am not there. Often I find a problem with a car almost instantly, either I see something or just hear something from how it runs. That does not transfer over the net. This is all based on what you describe and how it gets interpreted.
Basically the biggest concerns are the exhaust system, when you say it was smoked when was that? and static may not reveal the leak, sometimes you need pressure.
The other thing is electrical fault but I would expect codes from random faults. Since the car has been in storage I would be searching high and low for signs of a rodent, sort of as an also. Rodents love to bare wires.
Maybe we can rule out exhaust leak by unplugging the O2 sensors(4) and see if the car runs better, I just don't remember if the car goes back to a base table and ignores the adaptions or uses the old when it sees no O2 signal. If it uses the old adaptions this will do nothing, but it is worth a try.
Something else to try is to have someone else drive and you watch the live data for the fuel trim and watch for spikes in different conditions, IE cruising accelerating etc. The O2 report too slow in INPA to get a good feel for them unless you log them and then graph them, but you still might see something where 1 or 2 hang, but then again that could be the com lag with INPA getting it to the computer screen.
Maybe you need to figure out a way to seal up the engine and pressurize it. The plywood plates are simple if you have a saw and my exhaust caps were ABS temp drain plugs, but I have a Tubi exhaust so the diameter is different. As far as getting air in a vacuum line going to the plenum would work. I think someone used the vac line to the fuel pressure reg and said it worked, but you would still need to seal the dipstick because it will pop out with1/2 psi. The fitting I made was complex but a rubber hose and some clamps might get you there. I have little faith that sticking smoke up the tailpipe would show a leak if that what was done.
 

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Discussion Starter · #20 · (Edited)
I will be unplugging the O2 sensors down stream and see what happens. That is something I’m capable of doing in my garage.

The voltage to the battery while sitting overnight was 12.3V brand new battery. Where are you located?

Video of 02s previous was a screen capture but this shows huger voltage
 
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