P1297 code

[strophius]

I recently replaced the MAP sensor, AIT sensor, cleaned the throttle body, and cleaned the MAF on my '01 A4 1.8t. Prior to this, the car was running perfectly but it had a small leak at my power steering pump banjo bolt, so I figured I'd replace a few sensors and clean the throttle body while I fixed the power steering leak.

After doing the above items, and performing the TBA via VAGCOM, I fired it back up and it was idling like garbage! Felt like misfires, but when I pulled the codes I had only a single P1297. Looking up that code seems to point to N249, DV, vacuum leaks etc, but the car was running just fine prior so I doubt it's those. I tried swapping the old MAP back on, but same code and rough idling.

I did push on the throttle plate a little while cleaning (drive by wire), could I have messed it up? It completed the alignment just fine...the MAF also had a little rust on the sensor surface and it's the original MAF...would a bad MAF cause this?

Any help would be appreciated!

Thank you

[strophius]

Played around with it some today. I tried starting the car with the MAF unplugged and it was worse (more stuttering, rpms dropped and it almost died). I plugged the MAF back in and watched the readings on VAGCOM. While doing the warm up (1200rpm) the readings bounced between 6 to 9 GPS and the car was idling okay (it did seem to shudder slightly when the GPS would hit that higher mark) , then it suddenly jumped to around 12 GPS then the car started sputtering. The rpm was still around 1200. You can smell gas strongly from the tailpipe so it's definitely dumping extra fuel.

After the warm up, when the rpm dropped to the 800rpm range it was still reading almost 9 GPS at the MAF. I pulled the sensor out again and cleaned it with q tips and MAF cleaner as best I could. The metal plate near the bottom looks good, but there are also two prongs that stick out. The upper one (nearest the electrical plug) looks fine, but the lower one is completely rusted.

Does this point to a bad MAF?

[walky_talky20]

For other's reference: P1297 = "Pressure Drop between Turbo and Throttle Valve (check D.V.!)"

I think you may have a boost leak somewhere between the turbocharger outlet and the throttle plate. This would explain your high MAF value and richness (losing metered air). Generally this has to be a moderate sized leak somewhat close to the turbocharger.

What are your fuel trims from block 032?

[strophius]

That just seems so odd...how would I suddenly have a boost leak after it was running fine, I noticed some drips of power steering fluid on my garage floor, so it was sitting for about 4 days while I got some stuff together, then replaced that along with those sensors and started it back up. I haven't even driven it, just idling for a minute or so.

Wouldn't a vacuum leak at idle cause a lower MAF reading since pressure in the system is reduced and hence draws less air through the air filter? I'm also confused what that code is specifically saying, meaning, what sensors is it using/comparing to throw that code? The nearest air sensor to the throttle body would be the MAP sensor (technically the IAT is right there, but I don't think that reads pressure or flow?). So is that code just comparing MAP readings to MAF readings?

I'll jack the car up tonight and look around the turbo outlet pipe and DV. I checked the intercooler->throttle body hose (only one I actually removed) for leaks, but it's a silicone hose and everything is clamped down tight. I'll log the fuel trims when I get home tonight.

Thanks Walky, really frustrated as the car has been running great....should have just done the stupid power steering leak and left the sensors alone..

[walky_talky20]

how would I suddenly have a boost leak after it was running fine?

Things are allowed to fail whenever they want to. It does absolutely make sense to triple check the things that were touched recently, though.

Wouldn't a vacuum leak at idle cause a lower MAF reading since pressure in the system is reduced and hence draws less air through the air filter?

Yes. If the engine only makes vacuum, then leaks will always be of the "vacuum" variety. But your engine has an air compressor strapped to it, so it can have pressure leaks. And it absolutely can create such air pressure (albeit just slightly) even at idle. A leak very near the compressor can lose metered air at idle. I've seen this and fixed it myself on a 1.8T. This sort of leak is somewhat rare (probably the rarest type, honestly), can pretty much *only* happen on a turbo car, and can usually be confirmed by a negative idle (additive) fuel trim. So you should check for a negative idle fuel trim.

what sensors is it using/comparing to throw that code?

Wow. I am very impressed with you, sir. I think you would make a fantastic diagnostic technician, if you are not one already. This is absolutely the best question anyone could possibly ask in this case. You are not asking "what is my problem? how do I fix it?". Here you are asking "what is the ECU thinking?" and it is this type of logic that is critical for diagnostics. You have 1 fairly weird code - so you don't have the option to choose a more straightforward error to dive into first. So it would make the most sense to find out exactly what factors would lead the ECU to set that specific code, if such knowledge is available.

So is that code just comparing MAP readings to MAF readings?

I think you are right on the money. It is not a single sensor that sets this code. It is more so a "behavior" regarding air flow (MAF) and air pressure (MAP/BOOST) that do not make sense together. Possibly factors in throttle position data as well. I have to say that I, not being an Audi technician, do not have the exact definition for what sets this code. I don't believe I have access to the detailed "Motronic Strategy" documents that would hold such information either. All I can say is that I believe it is seeing a pressure/flow situation that does not correlate. Most often the cause is pressure spikes from a torn DV or pressure dips from a moderate to large charge piping leak.

[strophius]

Thank you Walky, I am not a diagnostic technician, just a dude who wrenches on his cars, but I really appreciate the feedback! I totally get that things can fail at any time, it just seemed odd because I've had my turbo outlet hose pop off while driving before (was years ago, and my fault for not checking the clamp) and it didn't throw this code or cause this type of engine behavior. I actually repaired a large tear in one of my DV hoses (don't remember which one, but not the small vacuum hose) about 3 months ago and double-checked everything else down there, but funny thing was, there was no code and I actually didn't notice much of a difference after the repair.

Yeah I couldn't find a lot of definitive information about this specific code but was hopeful somebody had more insight what information the car was pulling to determine there was a problem.

My mind keeps drifting to the throttle body hose as that was the only hose I actually removed...I'm going to quadruple check it as well as the throttle body gasket (I replaced that too) and do the bubbly water test along with pulling those fuel trims when I get home.

[strophius]

Okay, checked the intercooler to throttle body hose, it's on tight and no leaks. Group 32 showed 0 percent the whole time it did the warm up. The engine load seems high though. Here is a video

https://youtu.be/x7n4OD9OBvY

I also did the TBA while watching the throttle, another video:

https://youtu.be/3Qic2wWcWRQ

Is that normal? Seems to be hissing a lot.. But it says it completes.

[strophius]

I checked again this time with measuring group 033. It showed 26.6% with a voltage of 3.140 once it finished the warm start.

It's so strange. When starting it, it idles fine for about a minute before the stuttering starts...

[strophius]

Well got it resolved! Turned out it was the throttle body, apparently I damaged it while cleaning.

Got an almost brand new MAF and a really crappy looking throttle body from a local junkyard. Unplugged the battery, swapped the MAF first, plugged the battery back in and checked codes before starting it.

It had a two new codes I hadn't had before P1568 (throttle actuator - mechanical failure) and a P1579 (throttle actuator - adaptation not started) and they would not clear. TBA showed an error state

Odd thing was just removing the key, then going back to acc power allowed the codes to be cleared and it ran the TBA fine.

Started it up and same behavior, so unplugged the battery, installed the crappy junkyard throttle body, and boom! Idled just fine! Seem to drive fine as well, but going to see about a new throttle body regardless.

Thank you for the help Walky!

[walky_talky20]

I think this confirms P1297 does use throttle plate angle as part of it's logic. So that is good to know.

Thank you for the follow-up, I would not have expected such an outcome. The VAG DBW throttle bodies are generally fairly trouble free.

Regards,
Walky T.

[strophius]

Thanks Walky, yeah the car also feels much more throttle responsive and snappy (if that makes sense) when getting off the throttle then I've ever felt in my 12+ years of ownership, so perhaps my old throttle body was having issues for some time. After driving for a day (mostly highway, with a few WOT pulls while merging) I got a CEL for system running rich (apologies I don't remember the exact P#). I looked at the short term (group 033) and long term (group 032) fuel trims and my short terms are near perfect (+/- 3) but my long term is pegged at -24 hence the CEL.

The car drives better than I've ever felt (boost builds faster and the car feels like it's pulling harder) so I don't want to mess with anything. Watching the STFT (group 033) while driving around shows it being very stable, even under WOT so I'm not really worried. I'm guessing maybe the LTFT (group 032) shows such a high negative value because the system was flooded with so much extra fuel during my troubleshooting. I'm wondering though if that may indicate an adjustment to the tune may be needed? I'm running a custom Motoza tune.

[walky_talky20]

-24% long term trim is a bunch-ton. Is that the additive or multiplicative? Additive=idle, Mult=Part Throttle.

High negative trim is almost always going to be a boost leak (loss of metered air because the air is pressurized). Relationship between Add and Mult trim will give you an indication of whether you are dealing with a leak that is "boost only" or "boost and vac". With that much trim, however, there is some chance that the fuel pressure is incorrect (too high). Pulling out 25% of your fuel map is a huge adjustment. Also with custom software, we can't be quite as sure of anything as you could be with stock software.

[strophius]

It's on the multiplicative side, idle one is +1%

Yeah I'm definitely leaning towards the tune needing adjustment, especially since the car actually performs better than before. It even builds boost faster! I'll do a leak check though just to rule it out.