HP Fuel Adaptation Value

[ma77hewsu11ivan]

Looks fine. Calling for and getting 40.0k mbar What happens when you go for throttle-up?


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[TomBelgium]

The actual value is only 40mbar while the setpoint value is 40000mbar. Or am i misunderstanding the piwis values?

[ma77hewsu11ivan]

The actual value doesn't read 40. It reads 40.0k Again, what happens when you drive it?


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[TomBelgium]

1 hour ago, ma77hewsu11ivan said:

The actual value doesn't read 40. It reads 40.0k Again, what happens when you drive it?


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When i start the car after a couple of hours standing still i get a very rough idle, like it is misfiring. It also take about 5 to 10 seconds before the car starts. 

The rough idle goes away after +- 30 seconds OR when i revv the car a little bit. Then it goes away and idles 'normal' however even then i don't think it is that smooth as it should be.

I also notice a lack of power when i fully press the acc. pedal. It's just not as smooth or powerfull as it should be even when the rough idle is gone.

[TomBelgium]

16 hours ago, ma77hewsu11ivan said:

The actual value doesn't read 40. It reads 40.0k Again, what happens when you drive it?


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Ok i tried with another OBD reader. Seems like you are right. This ones gives me indeed 40 bar actual value at idle. When driving it goes to around 120bar max. But i do notice that my actual value is fluctuating around the setpoint value. not a lot but when it should be 40bar it sometimes goes to 36  bar or 42 bar etc.

 

 

But since the biggest problem is at the startup i wonder what the high fuel pressure should be when the car is turned off?

Edited July 12, 2017 by TomBelgium

[ma77hewsu11ivan]

You have all the pieces. Time to solve the puzzle. I'd start with a pressure test and flow rate to make sure your LP pumps are getting enough fuel where it needs to go. If the pumps are original, you'll want to replace both along with fuel pressure regulator and filter regardless as the originals WILL fail, but that's a bit pricey... Could be just a dirty throttle body, a failing FPR, a semi-clogged fuel filter, injectors, coils, plugs, crappy gas, weak battery, wire weirdness...


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[ma77hewsu11ivan]

When entering the vehicle after it's been sitting for a time, do you hear the fuel pumps prime when you open the drivers door?


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[TomBelgium]

I will check that tommorow, i am leaving the car 24h without starting to check the high fuel pressure to see how much is gone after 24h.

Do you know what high pressure value it should have with the engine off? I believe it should be at least 40 bar so it can start easily because the idle requires 40 bar too.

I am just trying to eliminate possible failures.

Edited July 12, 2017 by TomBelgium

[TomBelgium]

Seems like piwis can give me more useful information about a P1023 that i got. As you can see the actual value at startup is ten times lower as required.

[AirShox EU LTD]

On 7/13/2017 at 12:54 AM, TomBelgium said:

Seems like piwis can give me more useful information about a P1023 that i got. As you can see the actual value at startup is ten times lower as required.

Hi there, 

Incredible thread!

I am trying to find out why when kick down (3rd, low speeds into 2nd or 2nd into 1st) my CTT 4.8 2008 I Intermittenttly get 1 to 4 misfires on cyl 1 and 5. Mostly cyl 1. Using the "misfire counter, 10 trips", which shows what happened after a key cycle. 

No fault codes, hp adaptation is ~1 (0.9x to 1), idle is at 39-40bar (is there an ecu politics to fluctuates 36 to 40 when tank is under 15L (both LP pumps continuously on). 

Spark plugs are brand new, coils are relatively new (less than 6k miles, no cracks). When I changed the spark plugs, intentionally mixxed coils in ordered to eliminate possibility of a weak one. 

Regards 

[GlenC]

Interesting read..

I am having a problem with my 2008 Cayenne S

Had a fuel filter crack and leak, so replaced that.

About 3000mi later started having fuel pump problems (at 1/2 tank it would shutdown while driving) Ultimately when it shut down, I could pull a pump fuse and it would run on one, not the other.  With 137K miles, I replaced both pumps. Everything seemed fine.

 

A few hundred miles later, I drove the car 20 miles to a friends house.  A couple hours later, we went to leave, started normally, but in about 5-10 seconds, started running very rough and shut down.  3-4 restarts the same.  About 4-5 hours later, I went to leave, thinking I'll need to call AAA, however it started and ran normally.  It was normal for the next few months and few hundred miles.  

 

Now about 200 miles later, the problem has become very frequent.  I did manage to get it to run, started driving home, however noticed it would falter if I tried to accelerate ...... drove 20 mi home no issues driving easy.

 

Today, checked Durametric and code 1025 was there. Started and ran, HP setpoint = 40, HP actual was about 36-44.  Graph of actual value was like a wavy saw blade.... 1 mb fluctuations in the values as values went above and below the setpoint.  Cleared code 1025 and it returned.  The Fuel high-pressure adaptation values 1-5 range from 0.9 to 1.25  Fuel high-pressure adaptation range 1 = 1.0

Went back out to drive car with Durametric running.  Cleared the 1025 and CEL went out.  The fuel HP values seem to closely follow the setpoint.  This time there was no faltering while accelerating, everything seems normal.  The difficult part is this may act normal for >100 miles or <20 miles, I won't know until it happens.

 

Anyone with the Durametric, How smooth is your actual HP Fuel value and how much fluctuation compared to Setpoint?

 

Unfortunately, I have a family trip planned, towing the Airstream, in 8 days....  I need to find the problem.

At this point, I'm leaning towards replacing the HPFP....