Loss of power uphills

[vw_man99]

Hi All,
Recently my 2015 Q5 2.0T TFSI is loosing power from standing start especially going uphills. It almost seems like there is no boost going uphill. There is no check engine and vagcom shows no errors. Did some test runs on the highway with Torque app shows 16-18PSI of boost. The DV and PCV were replaced but made no difference. Once its moving on flats its ok but not like before. No obvious leaks I can find but I can hear a hollow air flow when driving. Have to drive up hills on a daily basis so this is getting frustrating. Q5 forums tend to be quite so figured I would try here. Any recommendations for next steps would be appreciated.

vw_man99

[beatsageo]

Can you post a quick scan with VCDS? Check the intake path first. Make sure the filter in in working order. Make sure all the clamps are tight from airbox to turbo, make sure MAF is plugged in. Check turbo outlet hose clamps to intercooler. Check outlet of intercooler all the way up to throttle body. Check all connections on the intake manifold are attached and clamped, I have had a PCV hose pop off before. After those checks I would check fueling, can you log data?

[vw_man99]

There have been absolutely no permanent/temp errors when scanned with VCDS. It idles smooth, just lower power output recently.
- MAF is plugged in - all ok
- Checked the PCV hoses - seem ok
- Air filter was replaced couple months back but will check and make sure air box screws and hoses
- DV replaced early summer just for maintenance (Pierburg)
- Torque showed fuel trim in <5% which I think is ok.

Never logged data with VCDS before so will look that up. Do I log turbo requested vs actual or something else?
Big storm passing through so will check lower intercooler hoses when it clears up.
Thanks.

[beatsageo]

Its curious that you say its "down on power" but the ECM is not reporting anything. Since your not misfiring lets target (Air/Fuel), start with boost requested, boost actual, Intake air mass, RPM, Throttle angle, and Lambda(actual), fuel rail pressure. Yeah the fuel trims (long and short term) less than 5% are good. Going up a hill fuel pressure and boost build so maybe something going on there.

[a4audi4fun]

What mileage are you at? Might need walnut shell cleaning for carbon buildup on the intake valves. Had similar problem with my 2008 at 195,000km (~121,000mi). Cleaning brought my engine back to life. I wasn't getting any error codes, but VCDS logging confirmed actual boost was not getting anywhere close to specified boost. Log Group 115.

[vw_man99]

Mileage is 155,000km. Are there no errors logged when actual boost is not close to specified? It is weird there are no codes based on the lack of power. I pushed it hard last week but still nothing. Even my wife was saying it does not sound like usual. Will try a VCDS logging run this weekend.

I have a cheapo boroscope so may try to view the valves through an intake intake manifold opening. Has anyone had success using a boroscope without taking the intake manifold off?

[a4audi4fun]

Under full throttle I was reaching about 50% of my specified boost. Driving around town at normal levels 1500-3500 RPM things felt OK as I was getting partial boost for partial throttle; it was the 3000+RPM under full throttle that I noticed it.

As you are in Vancouver try The Cut in North Van as a test area, even with traffic around, you should be able to accelerate from 60km/hr to 90 km/hr easily in 3rd, 4th or 5th gears. before my cleaning 4th and 5th felt really gutless, now it's all fine.

[vw_man99]

I went from Burnaby to Park Royal Mall up the highway past weekend, along The Cut. Once I get moving top end power is kinda ok, but off the line or up hill is bad. Will try to do the VCDS logging after work and may pull the recently replaced DV on the weekend if the weather holds up.
Thanks for the quick followup!

[vw_man99]

Did couple of test runs and logged data - first time I tried logging/graphing.
Seems the actual boost never drops below specified, or am I supposed to subtract 1084 for the ambient. Included longer run with several sprints and the zoomed in for closer view.

[vw_man99]

Mmmm, not seeing the images posting, here are the links to the images
Couple of sprints https://imgur.com/qHrSj2W
Zoomed https://imgur.com/HZvMcAe

[a4audi4fun]

Maybe time to get that boroscope of yours working.

Have you got the raw .csv for your runs. PM them to me if you can. I subtract ambient pressure from both spec and actual to determine what actual boost is being asked for. Spec less than 1084 means you are in idle or throttle closed mode (i.e. vaccuum). Any chance you have the spec and actual numbers reversed? In your 1st post you mentioned 16-18 PSI, so after subtracting 14.7psi for ambient you are getting 2-3 PSI. For a stock engine I'd sort be expecting 5-8 PSI. Stage 1 on my B7 after the carbon clean is in the 17-19 PSI boost range.

Does seem like there's a lag between spec and actual though.

Suspect the only time you would get an error code for underboost is if there is zero or close to zero boost - rest of the time the ECU thinks it just needs to have the turbo wastegate open longer to help build more boost. You could measure the wastegate cycle to see how long that is being kept open?

Sorry for all the questions back but there are just so many things that have to be working perfectly for optimal performance. PM if you want to talk by phone about this stuff.

[Theiceman]

Plugs... Change them. These cars are hard on plugs.


Sent from my SM-G973W using Audizine Forum mobile app

[vw_man99]

Plugs/coils were changed last summer when I brought the car with NGK plugs and Bosch coils. Idle is smooth so doubt they would be bad.
Thanks.

[Theiceman]

Plugs usually fail under load. Not idling. But if they are the correct spec plug they should be fine .

Guess need to log some data. .. fuel pump issue maybe ?

Sent from my SM-G973W using Audizine Forum mobile app

[beatsageo]

If you have the raw file can you post it/send it? Your boost pressure curves don't look out of whack. your peak boost is ~15.3psi (2000Hpa-1013Hpa(atm)). Can you confirm your intake runner flap linkage is operable? Additional useful data would be fuel related data. Lambda/fuel pressure/injector 1-4 pulse width/duty cycle.
intake.jpg

[vw_man99]

Put back my original DV (revC) instead of the one replaced couple months ago (Pierburg revD) and seems little better but maybe thats my wishful thinking but still not back to previous performance. Scanned car today and still no permanent/temp errors.
Checked fuel values at idle, HPFP:39.870bar, LPFP: 6.478bar. Didn't check the runner flap linkage yet.
Have a new tank fuel filter but need to get the gas level down before replacing.

So next run I will log: boost actual, boost specified, fuel pressure, RPM, throttle position - any others to log?
Thanks.

[TomsMR2]

Its your turbo. Your turbo is shot. I bet it rattles when you rev it when parked.

If you want to set the fault, put the car in manual mode and accelerate 5 times from 1000rpm to 5000rpm. The pedal has to go all the way to the kick down point, but not past, so it doesnt kick down. After it sets, bring it in to audi because you should have the crazy long turbo warranty on it.

[vw_man99]

No rattle or smoke. Did the acceleration test you mentioned in manual and no codes. If there are no codes then dealer is not going to replace it. I mentioned before there a hollow air sound when driving which was not there before but can't pin it down. Besides the DV, what other valves could it be? Maybe I just have to wait till it generates a code. Plan to do a valve cleaning after winter. May drop by the local Audi group meet to see if others hear/feel the same things.

[vw_man99]

Replacement DV was purchased from Amazon and intermittent after 8 months. It came in Pierburg blue box, had Pierburg silver sticker covering part numbers and Pierburg logo elsewhere. Under the Pierburg silver sticker other logo is grinded away. So seems a fake part (?)
https://imgur.com/mctKqt3
https://imgur.com/Z8pfy4H

Also has a QR type code on the Pierburg box label which iphone does not pickup.

Heres an interesting article about fake Pierburg parts
https://www.heartbeat-online.de/en/n...-coolant-pump/