Stumped by S52 throwing P0170 P0173 - Don't know what to try next

[RenaissanceMan]

I'm hitting a wall trying to solve my check engine light issues and could use some help. Car is an E30 with an S52/OBDII conversion. After clearing codes, STFTs will soar to +25% before jumping to 0% when codes are thrown. Of course, I first suspected vacuum leak(s). I smoke tested and found a small leak at the dipstick o-ring and the CCV, so I assumed that was the problem. Replaced the o-ring and CCV with new and smoke tested again. No leaks. Ran the car, and the same exact codes returned. Since then I've also replaced:

- Fuel pressure regulator
- Intake manifold gaskets
- Both pre-cat 02 sensors (my Markert ECU tune has the post-cat 02 sensors flashed out)
- Entire CCV assembly
- MAF

Full disclosure, I replaced my MAF with another used MAF, so I guess I'm not 100% sure that it is working perfectly, but I hoped the odds would be in my favor.

At this point, the only other thing I'm thinking of testing is the fuel pressure, but if that check out as well I'm at a total loss. If that turns out to be the case, what else could I look at? Could a short in the harness wiring or a failing ECU cause these consistent types of symptoms? Any help is greatly appreciated!

[bmwdirtracer]

I'd advise not worrying about wiring harnesses or the DME itself, as long as it's the one made to run that engine.

Now, you DO have a tune....and Markert is well known to create good things. However, are you sure that the tune matches all your criteria? (i.e.: If the tune was supposed to be working on a given set of injectors, or maybe a larger throttle body/ bigger cam, etc., you may have a single factor wrong that's throwing off the calculations). Are you sure that's what you're running?)

Yes, first step I'd recommend is establishing the fuel pressure is correct. Then, you absolutely need to connect to a better scanner, that reads actual BMW codes, not just generic emissions codes. Please tell us what the LTFTs look like.

You also should consider sending your injectors off to RC Injection for ultrasonic cleaning/"blueprinting" and testing. Only about $26 per injector.

More testing, establishing the basics, is needed before starting to question the DME's integrity. You're hunting a fuel air issue, stick with that for now.

[328 Power 04]

Did the issues start recently, or were they like this for a while?
What changed?

[RenaissanceMan]

However, are you sure that the tune matches all your criteria? (i.e.: If the tune was supposed to be working on a given set of injectors, or maybe a larger throttle body/ bigger cam, etc., you may have a single factor wrong that's throwing off the calculations). Are you sure that's what you're running?)

Did the issues start recently, or were they like this for a while?
What changed?

Thanks for the replies, y'all! So the car has been running without issues/codes for years. This issue with the codes is something new that has started in the last several weeks. I did the drivetrain swap, myself, and made sure that Markert set the tune up correctly for my configuration when I put the car together. Nothing had changed on the car before the issues started.

Definitely going to check fuel pressure next. In the meantime, I did also run codes using INPA and also a Peake reader I had laying around. INPA is showing the following codes:

202 Lambda Regulation Bank 1 Pre Cat
203 Lambda Regulation Bank 2 Pre cat

I've also attached a screenshot, but unfortunately I can't read German. I just looked up the code numbers and compared them against MS41 DTC data to get the specifics. However, the INPA codes are confusing to me, because they show 'Post cat' faults even though my car has those flashed out...

According to my Peake reader, these are the codes:

- O2 sensor adaptation limit, Cyl # 1-3
- O2 sensor adaptation limit, Cyl # 4-6

I will pull the LTFTs and post those tomorrow. Thanks again for the help!

[RenaissanceMan]

Fuel pressure according to my Harbor Freight tester (hope it’s at least remotely accurate!) is 3.3 bar with the vacuum line disconnected from the FPR and about 2.9 bar with it connected. Both readings were at idle 800 rpm.

LTFTs are stuck at 0.00%…. Which is very strange I think. I’ve monitored values like these successfully before using Torque on my E53 so I know the connection works.

Thoughts?

IMG_2354.jpg
IMG_2355.jpg


Sent from my iPhone using Tapatalk

[328 Power 04]

Thanks for the replies, y'all! So the car has been running without issues/codes for years. This issue with the codes is something new that has started in the last several weeks. I did the drivetrain swap, myself, and made sure that Markert set the tune up correctly for my configuration when I put the car together. Nothing had changed on the car before the issues started.

Definitely going to check fuel pressure next. In the meantime, I did also run codes using INPA and also a Peake reader I had laying around. INPA is showing the following codes:

202 Lambda Regulation Bank 1 Post Cat
203 Lambda Regulation Bank 2 Post cat

I've also attached a screenshot, but unfortunately I can't read German. I just looked up the code numbers and compared them against MS41 DTC data to get the specifics. However, the INPA codes are confusing to me, because they show 'Post cat' faults even though my car has those flashed out...

According to my Peake reader, these are the codes:

- O2 sensor adaptation limit, Cyl # 1-3
- O2 sensor adaptation limit, Cyl # 4-6

I will pull the LTFTs and post those tomorrow. Thanks again for the help!

These codes in my INPA are actually:

202 fuel trim limit Bank 1
203 fuel trim limit Bank 2

Makes sense. You should be looking at short term trims.


If I am to understand correctly, I didn't clearly get it from the message, it started doing this randomly just now? Then it wouldn't be the tune if the tune had been used for a long time.

[RenaissanceMan]

These codes in my INPA are actually:

202fuel trim limit Bank 1
203 fuel trim limit Bank 2

Makes sense. You should be looking at short term trims.


If I am to understand correctly, I didn't clearly get it from the message, it started doing this randomly just now? Then it wouldn't be the tune if the tune had been used for a long time.

Correct, started this randomly. I don’t think the tune is the problem. It has been fine for years.

Thanks for the clarification on the INPA codes. That makes more sense now. The chart I referenced must have been incorrect.


Sent from my iPhone using Tapatalk

[bmwdirtracer]

While your fuel pressure is okay at idle, I'd wonder whether the STFT reads +25% at idle, or is it just when you add load? If only when loaded, does your fuel pressure drop when driving?

Since the codes suddenly began occurring on both banks, and you have done a smoke test, it seems likely that fuel delivery/volume might be the culprit. You might try taping your gauge to the windshield, and seeing if the pressure drops under load, indicating a fuel volume issue, like a clogged filter or failing pump.

Did you do ANY work just before this issue began?

[RenaissanceMan]

While your fuel pressure is okay at idle, I'd wonder whether the STFT reads +25% at idle, or is it just when you add load? If only when loaded, does your fuel pressure drop when driving?

Since the codes suddenly began occurring on both banks, and you have done a smoke test, it seems likely that fuel delivery/volume might be the culprit. You might try taping your gauge to the windshield, and seeing if the pressure drops under load, indicating a fuel volume issue, like a clogged filter or failing pump.

Did you do ANY work just before this issue began?

According to Torque, I'm seeing the +25% at idle, after I've cleared the codes and restarted the car and it runs for a few minutes. Stays there for a bit then drops to 0%. Check engine light will come on even if the car never revs above idle. Not sure if that answers your question or not. The only thing I did to the car before this happened was change out a stuck thermostat.

[RenaissanceMan]

Had something interesting happen yesterday after a short test drive. Noticed a burning smell that smelled electrical to me and saw some smoke coming from the engine compartment drivers side right in front of the firewall. Looked with a flashlight and felt around all the wiring, harness, fuse box, etc in that area but didn’t feel any hot spots and couldn’t tell the source. Maybe it wasn’t wiring but it sure smelled like it. I’m really starting to think I have a short somewhere or something. I’m thinking I should do some continuity tests on the harness wiring between O2 sensors and the ECU. What do y’all think?


Sent from my iPhone using Tapatalk

[bmwdirtracer]

Your scanner reads live data? Check and see whether there's any anomaly in the temp sensor (air and ECT), or the MAF. An open circuited temp sensor would cause the DME to dump fuel because it thinks it's negative 40 degrees.

[RenaissanceMan]

Your scanner reads live data? Check and see whether there's any anomaly in the temp sensor (air and ECT), or the MAF. An open circuited temp sensor would cause the DME to dump fuel because it thinks it's negative 40 degrees.

Temp sensor live data is normal. Just ran the car again while checking data and now getting misfire codes on cylinders 4-6 out of the blue with a rough idle. Really starting to wonder if this is some short or wiring failure issue following that burning/smoking event.


Sent from my iPhone using Tapatalk

[RenaissanceMan]

Latest updates:

I downloaded the ETM for my motor and continuity tested all of the harness wires connecting the O2 sensors to the ECU. Also checked to make sure I had 12v at the O2 sensors and checked the grounds. All normal. Smoke tested one more time to make sure I had no leaks. But then I found something interesting... After clearing the fuel mixture codes, I discovered that the codes would return when just turning the key to "on" without cranking the car. In other words, the ECU is reporting fuel mixture data before it should even have gotten any of that data. For that reason, I'm assuming I have a problem with my ECU. Would y'all agree?

[bmwdirtracer]

Not necessarily. You might just have a problem with your scan tool.

At this point, I'm going to defer to Abel for his thoughts.

[328 Power 04]

Latest updates:

I downloaded the ETM for my motor and continuity tested all of the harness wires connecting the O2 sensors to the ECU. Also checked to make sure I had 12v at the O2 sensors and checked the grounds. All normal. Smoke tested one more time to make sure I had no leaks. But then I found something interesting... After clearing the fuel mixture codes, I discovered that the codes would return when just turning the key to "on" without cranking the car. In other words, the ECU is reporting fuel mixture data before it should even have gotten any of that data. For that reason, I'm assuming I have a problem with my ECU. Would y'all agree?

That's not a very good test of determining if the DME is bad.
I would think you'd have to clear the adaptations first so fuel trim data can all go to 0.

Secondly, if you smelled wire smoke and potentially have circuits shorting, I'd start chasing those issues as a lead!

[RenaissanceMan]

That's not a very good test of determining if the DME is bad.
I would think you'd have to clear the adaptations first so fuel trim data can all go to 0.

Secondly, if you smelled wire smoke and potentially have circuits shorting, I'd start chasing those issues as a lead!

Thanks for the feedback! Great points. I did not clear adaptations, so I will do that next.

Regarding the wiring, I pulled things apart and did extensive inspecting and I cannot find any evidence of burned or of a short as of yet. I suppose it’s possible I smelled something else but I will keep looking.

I’ll post back after clearing codes/adaptations and testing again.


Sent from my iPhone using Tapatalk

[Breeze1]

Based on your findings and everything that's been said so far, I'd look thoroughly at this "phantom post-cat" issue.

- Although wiring has been already checked, I'd double-check the physical connections of the pre and "post" cat sensors: have you inadvertently swapped the pre/post cat wires, especially where they meet/cross paths in the valve cover's vicinity? Has the wires' insulation been inadvertently stripped and created a short?

- About your tuning software, do you have access to the parameters section of the tune? If so, I'd make sure that the post-cat sensors haven't been turned back on for some reason (on the air software update, default/safe mode or whatnot.. I'm not familiar with this software and how it operates)

About the MAF sensor, I can tell you from personal experience that it could very well be messing up fuel delivery without triggering any codes. Since you've ruled out vacuum leaks and fuel delivery seems ok (short of the "windshield" test advised to you by Chris), try clearing the codes, disconnecting the MAF and going for a drive at low/mid/wide open throttle. If the car drives fine (that would also rule out fuel delivery issues) and the only code you get is the MAF sensor's one, you could have narrowed it down to that.

[RenaissanceMan]

Ok folks, wanted to report back with an update.

First of all, I think I located the cause of the short that I was smelling. There were 2 soldered harness splices on power wires from the e30/e36 connections to the relay block that were somewhat broken, and looked like they would have possibly have been making intermittent connection. Got those cleaned up and resoldered and so I can at least check those connections off the list.

Secondly, clearing adaptations did indeed prevent the faults from showing up again after just turning the key, so once again I'm able to start from a 'clean slate' after clearing codes.

Thirdly, I purchased a new MAF to rule out the unlikely possibility that both of my used MAFs were not functioning correctly.

I started using INPA only for monitoring the faults so I wasn't chasing codes in an inconsistent manner. Having said that, I'm still getting the same fuel trim faults. Here is a summary of what is happening consistently after I clear the codes and adaptations and start the car from cold:

1. Start the car - car idles perfectly
2. There is a 5 or so minute period which I'm assuming is the waiting for readiness period that I'm not seeing any fuel trim data being logged in INPA
3. After this 5 or so minute period, 'lambdaintegrator 1' and 'lambdaintegrator 2' readings go from 0 up to 64 and stay there for at least a minute or 2
4. After this minute or 2, both of these values will then return to 0. That is when the car will throw fuel trim codes for pre-cat sensors on banks 1 and 2 (202 fuel trim limit Bank 1
and 203 fuel trim limit Bank 2)
5. At no time do the 'adaptation value additive' or 'adaptation value multiplicative' values EVER move from 0. I have to assume this is a significant clue, since I should be seeing some kind of adaptation adjustments being made after the car has warmed up??

I've attached the 3 analog value pages from INPA that I screen-shot after the 5 or so minute warm up period. Another possible clue is that both the 'load [mg/stroke]' and 'needed air i.s. controller [kg/h] values are pegged with an exclamation point. (see analog 1 value page)

I could use some feedback if y'all have some insight.

Once again, here's a summary of everything I've done:

- smoke tested repeatedly
- replaced ccv and all seals/hoses
- replaced O2 sensors
- continuity and voltage tested all O2 sensor wiring
- replaced MAF
- replaced intake manifold gaskets
- replaced fuel pressure regulator
- verified fuel pressure with FPR connected and disconnected
- verified temp sensor readings as normal

I feel like the only thing left to replace is the ECU, right? I'm really getting frustrated with this.

Screenshot 2023-04-09 203457.pngScreenshot 2023-04-09 203512.pngScreenshot 2023-04-09 203445.png

[Breeze1]

From where I stand, three things stand out:

- your car is still registering post-cat sensors ("monitor sensor after cat") even though they are not physically present; that alone would make the DME register "infinitely lean" values, since it's looking for traces of fuel but can't find any, so it'll dump as much fuel as it can to compensate for that lean mixture
- probably because of the above, it's running in open loop constantly, thus disabling any lambda integrators / adaptative learning activity
- the load value is maxed out and the idle speed controller "needed air" is maxed out as well.

So fuel mixtures are messed up either by something downstream ("post" cat sensors management), or upstream (throttle body, idle speed controller), or none of those but possibly, as you said, a faulty DME.

I would try disconnecting all o2 sensors and see how the car reacts, both in terms of driving and in terms of live data / error codes. And again, do you have access to the parameters section of your tune? If the answer is yes, I'd check that the post-cat sensors haven't been turned back on, for some reason.

[328 Power 04]

The MS41 will not use the post cat sensor data for any mixture control

- - - Updated - - -

Load should be at around 100 when cold (dropping to 70-80 warm), and kg/h is correct. INPA just has the bar graphs calibrated funny, but the values are correct.

[Breeze1]

Thanks for the heads up about MS41, Abel. I never tuned on it, so I guess I was thrown off by the fact that the DME seems to be looking for the post-cat sensors. .

[bmwdirtracer]

I really have to wonder if the engine is achieving closed loop, at 165 degree F coolant temps. This engine should run at at least 187 degrees F.

[RenaissanceMan]

I really have to wonder if the engine is achieving closed loop, at 165 degree F coolant temps. This engine should run at at least 187 degrees F.

Chris, what would that imply if it hadn't reached closed loop yet? Pardon my limited knowledge, but if closed loop is the mode in which it starts monitoring A/F mixture, why would it throw codes in open loop mode? Are you saying the ECU might be thinking it's reached closed loop before it really has?

[bmwdirtracer]

Not really. I'm just saying that 165F is not a good operating temp. Let's suppose that the engine's actually running at the correct temps of, say, 190F, but the DME's injecting fuel to correspond to the 165 degrees being reported by the ECT sensor.

We're looking for an anomaly which might give you a clue towards why you're suddenly reading excessive fuel adaptation.

Do you have a smoke machine? Have you tried smoke testing the exhaust, to see if there might be a leak somewhere before the primary O2 sensors?

I'd mention the injector testing/cleaning/retesting at RC injection, again. It's not expensive, and would at the very least take one more possible culprit out of the question. Every set I've ever sent them from an "older" car revealed SERIOUS issues.

[RenaissanceMan]

Do you have a smoke machine? Have you tried smoke testing the exhaust, to see if there might be a leak somewhere before the primary O2 sensors?

I'd mention the injector testing/cleaning/retesting at RC injection, again. It's not expensive, and would at the very least take one more possible culprit out of the question. Every set I've ever sent them from an "older" car revealed SERIOUS issues.

Just smoke-tested the exhaust. No leaks from the headers or gaskets where they meet the head. However, I'm not sure if this is an accurate enough test unless I'm closing off the valves for each cylinder. Maybe y'all can chime in on that. What I do have is a leak at the gaskets where the collector bolts to the exhaust. And this leak is only about 2" behind the bungs for the O2 sensors. Even though it's behind the sensors, would a leak in that close a proximity cause a possible anomaly in what they are reading?

And for sure I'll look into sending the injectors off at some point soon.