Nightmare Fuel Delivery Problem is Driving Me Crazy

[colin08809]

Hello All

Sorry so long,
So I have been battling this fuel delivery issue on my Stage 2 2006 a4 2.0T Quattro for a while now and finally decided I should ask for help. It all started as a p2293 and p310b codes as well as sluggish pulls and occasionally limp mode. I first cleaned the MAF and throttle body and that didn’t do anything, so I replaced the fuel rail pressure sensor and fuel filter and nothing. Then a new hpfp with all new sensors and a cam follower and nothing! Decided it was the lpfp and the code went away as and so did limp mode! and for the first 30 mins of the new pump it was absolutely ripping so great, then it wasn’t? The car went back to feeling sluggish, my boost gauge doesn’t read 20psi (which is what i’m tuned for) instead steady-ish at 15 sometimes 10ish but no codes. I also use OBDEleven to check fuel rail pressure and it’s rock solid but my lpfp pressure is at 65psi and goes down under load, and also is not too responsive. Then did some research and decided I would get a new Fuel Pump Control Module, but still nothing changes. So I decided maybe it was the cheap lpfp from fcp euro and decided to get a new original audi pump. Installed it the other day and the only thing that improved was my mpg I am so deep in this and idk what else to do, I hear the high pressure relief valve on the fuel rail could be a problem but my fuel rail pressures are amazing. Also took my fuel pump relay out and it looked good but I still ordered a new one just to be sure.
new sparks and coils as well

If anyone could help me even a little on this I would be greatly appreciative!!
Thank You AudiZine!!

[Audibot]

I was gonna say 65 psi is low--my B7 would put out close to 6 bar (87 psi) at idle and at WOT, it would dip down to about 4.5 bar (~65 psi). You've changed those and the fuel filter, so it still being low is strange to me. Is it possible you have the wrong fuel filter? Ross-Tech has some helpful info: http://wiki.ross-tech.com/wiki/index.php/P310B/012555

Idk the history of your car, so to spitball a couple things:

Have you checked your fuel pressure regulator? (brass looking fitting piece). This thread goes over replacing it if needed.
Assuming you have an upgraded hpfp, have you checked that for wear too?

[colin08809]

Hello Audibot
I have not checked the hprv for wear, figured if it was an issue than my high pressure fuel pressure readings would be off, but they are within spec and very solid. For some reason just my lpfp readings are s*%it and boost is too, which I assume relate to eachother. Also the filter I have is the right one I’m sure of it.
I do have an upgraded hpfp piston, and I have checked the pump for wear but is still brand new since I replaced it in December, it came with new sensors and new fuel fittings, did not come w new banjo bolt tho so I reused mine.
Thank you for that thread it will be useful to me later


Thanks, Colin

[Jayz691]

310b is low side, as you noticed. Other possible causes are bad low pressure sensor, or a blockage somewhere. You said it's a 2006, so banjo bolt fitting on HPFP?

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[colin08809]

Hello Jayz691
Any idea on how to find a blockage? where to look? or clear it out? I have already checked my tank and it is spotless, and I have already replaced all fuel sensors Yes sadly it has the banjo bolt lol, but it is in good shape if that could be a concern. Is there like a specific way to reinstalling the bolt and I have just been doing it wrong?

Thank You, Colin

[colin08809]

UPDATE:

Put new relays in and figured I’d re-flash my tune as well, and I can’t feel a difference. I’ll attach a screen recording of obd11 for you all to see my pressures. Sometimes is worse than this, it’s weird.
Also my boost gauge usually shows me 15 psi every time I step on it, consistently, as I said in my original post my car is tuned for 20psi, could this mean a boost leak is causing the fuel pressure to drop? or is it more likely the other way around?

Thanks

https://youtube.com/shorts/g2KoMJ-ID...85Srm_FwNzFG05

[Jayz691]

Hello Jayz691
Any idea on how to find a blockage? where to look? or clear it out? I have already checked my tank and it is spotless, and I have already replaced all fuel sensors Yes sadly it has the banjo bolt lol, but it is in good shape if that could be a concern. Is there like a specific way to reinstalling the bolt and I have just been doing it wrong?

Thank You, Colin

I was asking if it was the banjo, cuz the rubber inlets degrade over the years, and can cause issues. Seems like your low pressure is meeting requested, so that's good(in your video anyway). Sux that the iOS version don't show duty cycle %, so can't see if the pump is working hard to keep up.


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[canadianA4B7]

Possibly 20 year old fuel filter?

[colin08809]

I was asking if it was the banjo, cuz the rubber inlets degrade over the years, and can cause issues. Seems like your low pressure is meeting requested, so that's good(in your video anyway). Sux that the iOS version don't show duty cycle %, so can't see if the pump is working hard to keep up.


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Ah man, it’s cuz I have IOS? I’ll have to ask to use my dads phone the, he has android. In the video it shoots up to 70-80 only after I let off the pedal, but as it’s fully open it slowly will go down to 55 or 40 sometimes. That video was a pretty good run cuz I was going down a hill though. Also I did not see any rubber inlets on the bolt, I have changed my cam follower multiple times too with no issue reconnecting the banjo bolt, so i’m not sure I have those?

[colin08809]

Possibly 20 year old fuel filter?

Nope, changed that already

[colin08809]

Here is another video I made driving the same road as the lpfp logs above^

It hits 15psi sometimes, maybe 17ish? I know it may be hard to see on video, but 12 o’clock is 15psi on the gauge.

[Jayz691]

Did you do a boost log? It's not about what PSI it hits, but if it's meeting requested, and WG duty cycle.

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[colin08809]

Did you do a boost log? It's not about what PSI it hits, but if it's meeting requested, and WG duty cycle.

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No I have not yet, I can’t seem to find the channel it’s on, I see some “boost” labeled channels but none of them seem to go above 10 psi so I feel i’m looking in the wrong place. Gonna use my dads Android today to do fuel logs to see if it shows duty cycle, any idea what channel to look at for that?

[colin08809]

Did you do a boost log? It's not about what PSI it hits, but if it's meeting requested, and WG duty cycle.

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Just did some logs, was not sure if I was putting the right channels and values so I put multiple, I believe the second and third readings are the same n75 duty cycle, and the lower two I thought were boost actual and specified, wouldn’t show me which is which though. I have a brand new n75 though and pcv, along with valve cover gasket, if that means anything.

Three videos in this Short,
First is a highway entry starting in 2nd gear
Second is pull in 4th gear on the highway
Third is another highway entry at 2nd gear


https://youtube.com/shorts/igx5nwZis...M1TdnThSNBnGlk

[Jayz691]

For boost ya want 115(req & actual) and 119(WG duty %).

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[colin08809]

For boost ya want 115(req & actual) and 119(WG duty %).

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Here is those channels along with lpfp pressure next to it
in order top to bottom
1.Channel 115 boost pressure (specified)
2. Channel 115 boost pressure (actual)
3. Channel 231 LPFP Pressure (specified)
4. Channel 231 LPFP Pressure (actual)

The rest are labeled good as seen in the video, if I made any errors let me know.
First video is highway entry in 2nd gear the next video is an entry in 3rd
Thanks for the info!

[Jayz691]

The only thing missing from that log would be lpfp duty %. Boost looks fine, actual basically stays with req, when on it. I see the low pressure dropping to about 3bar near the end of the pull. So the low side is struggling some, but even dropping to 3 bar, if rail pressure stays solid, "shouldn't" cause any issues.
What all was changed on the low side? Did you install a new controller? This is just a stage tuned car, correct? Stock turbo? Who's it tuned by? Remember these are load based for tuning/boost, so peak boost can vary with temp, elevation, etc. Looks like your peak req during those logs was 15-17psi.

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[colin08809]

The only thing missing from that log would be lpfp duty %. Boost looks fine, actual basically stays with req, when on it. I see the low pressure dropping to about 3bar near the end of the pull. So the low side is struggling some, but even dropping to 3 bar, if rail pressure stays solid, "shouldn't" cause any issues.
What all was changed on the low side? Did you install a new controller? This is just a stage tuned car, correct? Stock turbo? Who's it tuned by? Remember these are load based for tuning/boost, so peak boost can vary with temp, elevation, etc. Looks like your peak req during those logs was 15-17psi.

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I was gonna put lpfp duty cycle in there but ran out of room to view all of them, I do have it on the other video above though.

All new parts on low pressure side
- fuel filter
- lpfp(twice from fcp and currently using an audi one)
- the lpfp controller
- blew out the lines going to the fuel filter with air to see if any gunk came out, was none

All new parts on high pressure side
- new hpfp from CTS(used my og banjo fitting and bolt because it came with a bamboo fitting) with autotech piston upgrade
- fuel rail pressure sensor
- cam follower checked every oil change and replaced when worn
- fuel sensor on the hpfp sticking towards pcv

It’s a stage 2 HPFP upgrade Unitronic tune with some bolt ons, a high flow cat, straight pipe, cold air intake, and rs4 clutch kit

The high pressure side specified and actual remain the same and are strong, the weird part about all this is that when I FIRST put the lpfp on, my car drove insanely good, full boost and lpfp pressures in the 70s consistently, for like a half hour then started to give bad readings again.

only thing visably wrong with my car is my left intercooler hose has a tiny bit of oil seepage that comes back after I drive it, took the hose off and there was oil (not a lot) the hose looked good though, if it’s dripping oil could it also mean it leaks boost? it leaves no oil marks so minimal seepage.

sorry so long thanks again for your input lol

[Older_not_Wiser]

Does it run well again for a little bit after you clear codes? Clearing codes resets your fuel trims. Driving for a bit will adapt the fuel trims. If the adapted fuel trims make it run less than optimal then you may need to refresh your MAF and front O2. They both work but get worn out after 20 years. MAF controls your injector pulse time and front O2 fine tunes the injector on time and adjusts the fuel trim.

Look at what your LTFT is measuring block 032 iirc. Under 10% is OK and MAF and O2 prob OK, more than 10 (max is ~23 or 25) you are prob due for update on MAF and O2. Also check individual cylinder timing pull. When the fuel trim corrections are high, the ECM also pulls a lot of timing to keep the motor safe and it will not hit peak booost pulling all that timing.

[colin08809]

Does it run well again for a little bit after you clear codes? Clearing codes resets your fuel trims. Driving for a bit will adapt the fuel trims. If the adapted fuel trims make it run less than optimal then you may need to refresh your MAF and front O2. They both work but get worn out after 20 years. MAF controls your injector pulse time and front O2 fine tunes the injector on time and adjusts the fuel trim.

Look at what your LTFT is measuring block 032 iirc. Under 10% is OK and MAF and O2 prob OK, more than 10 (max is ~23 or 25) you are prob due for update on MAF and O2. Also check individual cylinder timing pull. When the fuel trim corrections are high, the ECM also pulls a lot of timing to keep the motor safe and it will not hit peak booost pulling all that timing.

Hello, to answer your questions, no clearing codes or even doing a battery reset doesn’t give me a difference. I clean my MAF sensor somewhat regularly, and intake filter. Below I have a video of all my cylinders in order 1-4 for timing retardation on channel 020, and I put what I THINK is LTFT on the bottom at channel 032. I will also post some pictures of the chart for each pull for a better analysis.

The first video is a highway entry in 3rds gear
The second is a high entry in 2nd
and I believe the third video is an entry in 3rd

I apologize the videos audio is bad and the very last video seems to be delayed with audio, not sure how it happened but the video itself is good.








I noticed the charts show cyl. 2 is pulling more than the rest, but is fine in the video for the most part. What would this indicate? Also noticed everytime I get on it my headlights flicker, the harder it pulls the more they flicker?

The charts may be out of order of when these pulls where done in the video, still figuring out how to post on here lol.

Thank you for your response and input and apologies for the long replies.

[colin08809]

Can’t figure out how to link pictures so here I posted to imgur lol

Here are the charts,
https://imgur.com/a/9Y1gu8Y

Thanks again.

[Jayz691]

What did you use you put the log into a nice spreadsheet? I've tried on obdeleven many times, but never works right.
Anyway, you're def getting a LOT of timing pull, almost 5° across all cylinders at times.
The trims to show are your partial, and 7% isn't bad. Mine sits around the same currently with no issues. See what your "idle" trims are as well.
I'd also check MAF(block 3) and Lambda/correction(31 & 33). Your trims don't come into play at WOT, and see what you're getting for MAF readings.

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[Older_not_Wiser]

Block 032 'Adaptation (Partial) Bank 1 Sensor 1' is LTFT and as Jay said 7% is not too bad.

What I was postulating is that when the MAF starts to wear out and you LTFT are getting bad, say 15%, that means the MAF is reporting 15 % less air than what is really passing the MAF and the O2 sensor is adding 15% more fuel to keep your lambda in the proper range.

But in this scenario, the ECU thinks you are still flowing less air and may do safety protections like not allow full boost or pull some timing. I am not a tuner so just postulating on what I have observed and that is with fuel trims over 15% I have seen not peak boost and high timing pull and switching out the MAF and front O2 got the LTFT back down in the low single digits and got all the boost and less timing pull. Car ran like it should again.

[colin08809]

What did you use you put the log into a nice spreadsheet? I've tried on obdeleven many times, but never works right.
Anyway, you're def getting a LOT of timing pull, almost 5° across all cylinders at times.
The trims to show are your partial, and 7% isn't bad. Mine sits around the same currently with no issues. See what your "idle" trims are as well.
I'd also check MAF(block 3) and Lambda/correction(31 & 33). Your trims don't come into play at WOT, and see what you're getting for MAF readings.

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My dad actually exported it into that chart since we used his phone because he has android. I asked him how and he said, “It came out of OBD11 as a .csv file, which is basically already a spreadsheet. Just open it in excel or google sheets.” would also help to be on desktop.

I did some pulls logging my MAF, I used channel 002 because it had the same info as 003 but 003 didn’t have the units. Also did some pulls on 031 and 033 in my video. Took a look at channel 032 as well again and partial was at 6.6% and idle was at 0.2%.



Thanks, Colin

[colin08809]

Block 032 'Adaptation (Partial) Bank 1 Sensor 1' is LTFT and as Jay said 7% is not too bad.

What I was postulating is that when the MAF starts to wear out and you LTFT are getting bad, say 15%, that means the MAF is reporting 15 % less air than what is really passing the MAF and the O2 sensor is adding 15% more fuel to keep your lambda in the proper range.

But in this scenario, the ECU thinks you are still flowing less air and may do safety protections like not allow full boost or pull some timing. I am not a tuner so just postulating on what I have observed and that is with fuel trims over 15% I have seen not peak boost and high timing pull and switching out the MAF and front O2 got the LTFT back down in the low single digits and got all the boost and less timing pull. Car ran like it should again.

I’ll clean my MAF again and look at it tomorrow and post a picture, am still confused how my headlights flicker under full throttle? Could this be an alternator problem? I have a newish battery already. Would something like that effect fuel delivery or readings?
Also, does that mean my MAF is reporting 7% less air? Sorry for all the questions lol, just trying to learn better about what these readings mean.

Thanks, Colin

[Older_not_Wiser]

So, in general yes, a +7% LTFT means the MAF is telling the ECU that 7% less air is is passing by it. 7% more air is entering the motor than the MAF is telling the ECU.

The MAF is the primary input for the ECU to tell the injectors what their pulse duration needs to be and therefore how much fuel is input to the motor. The front O2 sensor (and to a much lesser degree the rear O2 sensor) then checks the post combustion air fuel ratio and since the MAF is is reporting less air than what is really getting into the motor, the mixture will be leaner than it should be and that front O2 sensor then tells the ECU to increase the LTFT to add more fuel to get the post combustion mixture to target levels.

It is also a possible scenario that the MAF is reading air volume correctly and one or more injectors are not delivering the desired amount of fuel per pulse. The O2 sensor still sees a lean condition in the post combustion mixture and dials up the LTFT to bring it to target levels.

As far as your headlights flickering, I assume you have bi-xenons and usually flickering is just a sign that one or both bulbs are starting to go south. Not likely the alternator and not likely a contributor to fuel issues.

It can certainly be hard sometimes to pinpoint just what item is a little out of whack and causing reduced performance. The fact that it ran well for a short time after LPFP replacement would be where the focus should be.

[colin08809]

So, in general yes, a +7% LTFT means the MAF is telling the ECU that 7% less air is is passing by it. 7% more air is entering the motor than the MAF is telling the ECU.

The MAF is the primary input for the ECU to tell the injectors what their pulse duration needs to be and therefore how much fuel is input to the motor. The front O2 sensor (and to a much lesser degree the rear O2 sensor) then checks the post combustion air fuel ratio and since the MAF is is reporting less air than what is really getting into the motor, the mixture will be leaner than it should be and that front O2 sensor then tells the ECU to increase the LTFT to add more fuel to get the post combustion mixture to target levels.

It is also a possible scenario that the MAF is reading air volume correctly and one or more injectors are not delivering the desired amount of fuel per pulse. The O2 sensor still sees a lean condition in the post combustion mixture and dials up the LTFT to bring it to target levels.

As far as your headlights flickering, I assume you have bi-xenons and usually flickering is just a sign that one or both bulbs are starting to go south. Not likely the alternator and not likely a contributor to fuel issues.

It can certainly be hard sometimes to pinpoint just what item is a little out of whack and causing reduced performance. The fact that it ran well for a short time after LPFP replacement would be where the focus should be.

Thank you for the thorough explanation, as you can see I’m stuck, not sure what went wrong in the 30ish min I was driving it and it was working great. Also the low pressure reading sucking but my high pressure readings are solidHow would I go about checking the injectors out?
Also, I checked the MAF and it looked fine, cleaned it again, forgot to take a pic of it but I did snap one of this intercooler hose.

https://imgur.com/a/6Y4Hbpf

Ordered a new hose, my clamps seemed good. Not sure if this is causing any sort of boost leak but it is definitely leaking oil lol.

[Jayz691]

I’ll clean my MAF again and look at it tomorrow and post a picture, am still confused how my headlights flicker under full throttle? Could this be an alternator problem? I have a newish battery already. Would something like that effect fuel delivery or readings?
Also, does that mean my MAF is reporting 7% less air? Sorry for all the questions lol, just trying to learn better about what these readings mean.

Thanks, Colin

Voltage issues can cause all sorts of things, yes. See what you're getting for voltage when running, should be around 13.5-14v+.
The whole fuel trims just means your ECU is adding/pulling fuel from the base fuel table in the tune. It doesn't mean your MAF is reading wrong(reading 7% less air than what is actually passing), it's just adjusting fuel based off your 02 sensor readings. When the "idle" is high, it's usually a sign of a vac leak(unmetered air). Yours is solid at .2%.
A stock car would have more normal trims, but a tuned car with dif hardware, the LTFT's will vary, and that's OK. A custom tuner would add a little to the inj pulse, to bring down those trims, but with an OTS tune that's not possible. The ECU is doing what it's supposed to.
Another thing, I'd switch your units in OBDeleven, easier to read/understand metric(bar, G's, etc). I myself don't understand the lbs/min, used to G's, so can't say how the MAF sensor is reading.
When I was stage 2 Motoza(HPFP) I was hitting about 200g's peak, with a 200k mile turbo.

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[colin08809]

Voltage issues can cause all sorts of things, yes. See what you're getting for voltage when running, should be around 13.5-14v+.
The whole fuel trims just means your ECU is adding/pulling fuel from the base fuel table in the tune. It doesn't mean your MAF is reading wrong(reading 7% less air than what is actually passing), it's just adjusting fuel based off your 02 sensor readings. When the "idle" is high, it's usually a sign of a vac leak(unmetered air). Yours is solid at .2%.
A stock car would have more normal trims, but a tuned car with dif hardware, the LTFT's will vary, and that's OK. A custom tuner would add a little to the inj pulse, to bring down those trims, but with an OTS tune that's not possible. The ECU is doing what it's supposed to.
Another thing, I'd switch your units in OBDeleven, easier to read/understand metric(bar, G's, etc). I myself don't understand the lbs/min, used to G's, so can say how the MAF sensor is reading.
When I was stage 2 Motoza(HPFP) I was hitting about 200g's peak, with a 200k mile turbo.

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So I took a drive today and looked at my voltage and it was averaging around 13.8v. My units translate to 174g/s, I honestly don’t understand either lol, but this is how it was since I downloaded it. I guess it wouldn’t hurt to switch over.

Also today, I put a new stock HPRV on the fuel rail, and intake manifold gasket. Took it for another drive and still no difference. Not sure what the hek else I should do about this? Only thing left I haven’t replaced are the injectors. I just don’t feel like they are causing this issue though.

Thank you for the response and teachings