[dluney]

First let me say I'm a Mazda guy, so this is almost like a different continent for me. I have looked at the numerous other threads on the P0171 and the majority seem to be on turbo cars. I have a 2008 Beetle Convertible 2.5 BPS automatic. I bought it with front damage and rebuilt it for my daughter. It had a number of codes when I fininshed so I have thrown a boatload of parts and now am down to just the repeated P0171 Fuel Trim Bank 1: System Too Lean. I have done the following:
1. Replaced the PCV with the Dorman Kit
2. New fuel filter
3. New Bosch MAF
4. New Bosch O2 sensor
5. Sprayed everything I could spray with carb cleaner with no change.
6. Fuel pressure at idle is 44lbs
7. One not is coolant temp is showing 160-170, even in most stop and go traffic.

Drivability is still very good. Noisy at cold start, but I've read that's normal?
Once I clear the code, on cold start the STFT goes 20+, coming down just a bit after 160 degrees. LTFT pushes up to 18 or so then will move up to 20 then 20+ and it throws the P0171 before I can get Secondary Air and EVAP readiness.

I have an appointment to get a smoke test done as I have nothing left.

I welcome anything else people have done to fix this. Thanks in advance for your help.

 

[dluney]

Should have said, also did coils and plugs.

 

[billymade]

16555/P0171/000369 - Ross-Tech Wiki

Whew, you have thrown a TON of parts; at this car! Looking over what you have done so far and specific data you have provided us with: TWO things stand out, fuel pressure and your coolant temps, BOTH are off "normal" ranges.

Using this service manual with 2006 model; 2.5L BPS code, the fuel pressure spec is:

Fuel Pressure: Specifications

Fuel Pressure

At idle speed: approximately 4.0 bar (58 psi)

Ignition Off, after 10 minutes at least 3.0 bar (43 psi)

Keep going to the next page; to see all the info on fuel pressure testing procedures.

Volkswagen Workshop Manuals > New Beetle Convertible L5-2.5L (BPS) (2006) > Maintenance > Tune-up and Engine Performance Checks > Fuel Pressure > System Information > Specifications

So, right away; I question, the health of the fuel pump, we have seen quite a few "weak" pumps, on the 2.5L cause problems and throw a lean code. Your at 44 psi @ idle; compared to the 58 psi spec, I would want to see what your psi readings are, after 10 minutes, check residual" pressure and deadhead, maximum capable pressure, could reveal, more about the health of the pump. Many times the fuel pressure at idle; seems somewhat "ok" but under load, the pump, just cannot keep up with the needed fuel volume, for the engine, to run correctly.

Do you have any idea; how old the pump is, if it is original and how many miles theoretically are on the car/pump?

ALSO, keep in mind; that from what I can tell, the fuel filter, IS ALSO, the fuel pressure regulator and you might replace that, also You could start with the filter/fpr; as it is cheaper, then the fuel pump and will need, to be replaced anyway.

Your coolant temps seems low to me; full operating temps, seem to be in the 190-210 range and you are way, below that. You coolant temp sensor; could be off or you might have a stuck or weak thermostat. You might check for any "pending codes" and see if any, are related to the cooling system.

cooling temp sensor; testing/replacement:

Volkswagen Workshop Manuals > New Beetle Convertible L5-2.5L (BPS) (2006) > Engine, Cooling and Exhaust > Cooling System > Engine - Coolant Temperature Sensor/Switch > Coolant Temperature Sensor/Switch (For Computer) > Component Information > Diagram

coolant thermostat; specs, replacement:

Volkswagen Workshop Manuals > New Beetle Convertible L5-2.5L (BPS) (2006) > Engine, Cooling and Exhaust > Cooling System > Thermostat, Engine Cooling > Component Information > Specifications

So, while we can't see your live data; from what I can tell, those two areas, are "red flags" and the first one, would certainly affect your fuel trims, if your fuel delivery system is malfunctioning.

So, more detailed and different types of testing of the fuel pressure, replacing the fuel pressure regulator/filter (recheck for different testing results, etc); could shed some light, on possible problems with the fuel delivery system. Checking for pending codes and testing the coolant temp sensor, comparing temps shown in live data and comparing that with the use, of a infrared temp gun, could show a problem there and you might need to replace the thermostat, as well. Check things out and give us more info about the car, then we can go from there! Thanks!

PS: here was a long drawn out; thread, where we finally found the fuel pump, to be defective!

http://newbeetle.org/forums/2-5-liter-gas/85146-what-ignition-parts-can-fail-hot-motor.html

 

[dluney]

Thanks Billy, I did replace the fuel filter/regulator. I totally misread the fuel spec at 44,not 58. I read the 10 minute value and when the car popped right at 44 I thought I was spot on. Thanks for catching that. The car haes 132K and a plastic tank. I'll see if I can grab a good pump local if I'm too late for Amazon. Thanks again,

 

[billymade]

No, problem! As noted in the thread shown; DO NOT, buy cheaper aftermarket pumps, he had a AIRTEX and the car ran like *&*%^%*^ and couldn't keep up with the needed volume! Depending on what is available for your car; we have found to stick to oem ONLY fuel pumps, either BOSCH OR VDO, is typically, the oem for the various pumps, installed on our New Beetles. Generally, I would recommend; more testing, to confirm your pump is bad but that is a call you need to make!

Looking on the Bosch parts site; they list this as the right pump: (you might inspect the old one; by pulling up the back seat, remove the cover and see what the old one looks like and see what the part number is or look on VW's parts website to confirm.

https://parts.vw.com/

https://www.boschautoparts.com/en/

Part Number: 69740

This part compatible with:

2008 Volkswagen Beetle L5 2.5L

NOTE: installation restrictions: for vehicles with plastic fuel tank, without protective varnish DEFINITELY< try to confirm this; on your car and old pump!

https://www.google.com/search?ei=J9...30k1j0i30k1j0i8i7i30k1j0i8i30k1.0.mRq7yXTIAzQ

 

[LittleRedFlea]

I had the same code and as soon as I put in a new pump code was gone and has been gone!

 

[dluney]

Thanks Billymade and LittleRedFlea! So with a new Bosch fuel pump installed the STFT and LTFT and acting like they should, no more P0171!!!!!

Now if only I can get the EVAP and Secondary air to rediness I' and the tag office will be happy. I ended up over 3/4 tank so I'm hoping about a gallon or two from now the EVAP will set. I have a local shop tat has the full VagCom so worse case I'll pop into them for a forced monitor.

Thanks again and now just a matter of some oil drips to take care of.

 

[billymade]

Great! I'm glad; it was your fuel pump and we were able, to get that out of the way and bring your fuel trims, back into normal range.

Next, I would recommend; that you do some testing, to confirm your coolant temps are off and then, either the temp sensor or the thermostat, need changed or both?

As for the oil leaks; two seem to be common with the 2.5L engine, the oil filter cover and the vacuum pump, are notorius, for leaking.

The oil filter leaks on the front of the engine and the vacuum pump; typically runs down the side?

Here are some threads; discussing the problem and offering typical soluitions/options for parts replacement.

 

[billymade]

Oil filter housing:

http://newbeetle.org/forums/2-5-liter-gas/109866-oil-leak-small-filter-housing.html

 

[billymade]

Vacuum pump oil leak:

http://newbeetle.org/forums/2-5-liter-gas/146585-vacuum-pump-oil-leak.html

 

[Silver Mullet]

Question I have is, if the pump is failing and not able to keep up with the supply demand thus throwing a code, would it be able to maintain a highway speed without hesitation? I have the dreaded P0171. I have replaced the plugs and MAF. Also there is a rough jerking upon acceleration.

 

[billymade]

16555/P0171/000369 - Ross-Tech Wiki

wiki.ross-tech.com

What scan tool are you using; are these the only trouble codes and can you read live data? You have replaced the plugs and the maf; what brand were the parts (plugs: oem ngk or bosch; maf: oem bosch recommended)? There can be a number of issues; causing the lean code, I would check your maf readings for in spec, fuel trims (+or- 10% is considered in spec) and consider, doing a fuel pressure test.

Fuel Trim Info - Ross-Tech Wiki

wiki.ross-tech.com

https://www.ross-tech.net/vag-com/advertising/DiagnosingA_MAF_TechTip.pdf

For fuel pressure testing; give us the year, model,engine size/code, trans, etc; we can give you links to the factory service manual testing procedure.

 

[Silver Mullet]

2006 Cabrio 2.5 BPS 55K Auto. I have OBDeleven. MAF https://www.amazon.com/gp/product/B086RCH6C8/ref=ppx_yo_dt_b_asin_title_o05_s00?ie=UTF8&psc=1 Spark plug https://www.autozone.com/external-e...double-platinum-spark-plug-app5224/434630_0_0

 

[billymade]

How are the maf and fuel trim readings (e.g. live data)?

 

[billymade]

Fuel pressure specs:

Volkswagen Workshop Manuals > New Beetle Convertible L5-2.5L (BPS) (2006) > Maintenance > Tune-up and Engine Performance Checks > Fuel Pressure > System Information > Specifications

New Beetle Convertible L5-2.5L (BPS) (2006) > Volkswagen Workshop Manuals > Maintenance > Tune-up and Engine Performance Checks > Fuel Pressure > System Information > Specifications

workshop-manuals.com

testing:

Volkswagen Workshop Manuals > New Beetle Convertible L5-2.5L (BPS) (2006) > Maintenance > Tune-up and Engine Performance Checks > Fuel Pressure > System Information > System Diagnosis > Fuel Pressure Regulator and Residual Pressure Checking, Engine Code BPS

New Beetle Convertible L5-2.5L (BPS) (2006) > Volkswagen Workshop Manuals > Maintenance > Tune-up and Engine Performance Checks > Fuel Pressure > System Information > System Diagnosis > Fuel Pressure Regulator and Residual Pressure Checking, Engine Code BPS

workshop-manuals.com

 

[billymade]

Accessing live data channels in OBD11:

 

[Silver Mullet]

How are the maf and fuel trim readings (e.g. live data)?

I'm going to need to educate myself on how to see those readings using obd11. I did see a video on the short-term and long-term readings and have an idea.

 

[billymade]

Fuel trims, can help you narrow down the issue; typically, vacuum leaks and then, possibly a weak fuel pump or defective maf sensor. The 2.5L, is known; for a common vacuum issue, from a bad diaphragm in the pcv (valve). A bad PCV, causes a large unmetered vacuum leak; affecting fuel trims:

In general, an out-of-spec value in the first field (Additive: e.g. short term fuel trim) indicates a vacuum leak since it is mostly present at idle, when vacuum is highest. An out-of-spec value in the second field (Multiplicative: e.g. long term fuel trim) indicates a fault at higher RPM, and may point to a faulty MAF. (ross tech)

Dorman sells a repair kit or many say the RKXTech, is a better quality solution:

re: 2.5L PCV valve failure solutions from Dorman!

re: 2.5L PCV valve failure solutions from Dorman! The 2.5L; has a common issue, where the PCV valve fails. Up until now the only option; was to buy a whole new valve cover from Volkswagen (VW doesn't sell the PCV separately); at $225 or more, plus install... it is a pretty expensive fix with...

www.newbeetle.org

 

[Silver Mullet]

Yes I popped that off and took a look at it since it's an easy inspection. And it was in great shape

 

[billymade]

For fuel trim: try group 32: to see short and long term values.