Low power issue thats bugging me for a year... Seeking help

[Connor H]

whats up guys,

I have been trying to find this low power issue for about a year where ive exhausted myself of ideas.

It makes boost, perfect vacuum no leaks etc. but the car feels like its heat soaked 24/7. laggy and no torque at all. im thinking its something not playing nice with the tune anymore , maybe the ecu asking for less.

I have VCDS and there's no codes. Ive tried to log a few basic things but nothing stood out and im not sure what to look at next. So any guidance would be massively appreciated

No codes so completely stabbing in the dark

• Changed spark plugs no change
• Maf is reading low, but tried a working one with no difference
• Changed VVt unit last year to a decent but non OEM, no codes or issues after but tried a working OEM VVT solenoid and no difference
• Checked the TIP and turbo for mechanical issues, none except a small crack on the wastegate
• aligned the throttle body
• pressure tested
• cleaned sensors and TB
• car never overheats but it easily gets heatsoaked and stuck at 5psi from mild traffic

Im open to logging whatever needs. Ive attached a 4th gear pull (before i ran out of road) to get the ball rolling

Cheers

 

[mty12345]

All looks ok from those logs, i take it it's a stage 1 AUQ?
Could log the O2/lambda values for the fueling, think it's group 031 or 032
3rd gear is OK for logs too, 4th is a bit impractical seeing as your well into triple digits on whatever private road you use
What fuel are you using?
Would be good to log the knock/ignition delay too, can't remember what group that is off the top of my head, but the values are titled KW and the measurement units are in the format of 0.0degrees etc. Cylinders 1,2,3 are in one group and cylinder 4 in another

 

[Connor H]

hey mate

Its stage 2 so meant to be at 240hp, but definitely is down on power cos my mates stage 1 bora smokes me.

I checked the fuel trims on 032 last night, that was at -0.2% / 9.4%

using 99octane, tesco momentum or v power

i'll find out what blocks are knock/ignition delay and get back to you with some logs

cheers

 

[Connor H]

To return to this after a lot of crap got in the way.

I managed to log fuel and timing with no visible issues. its not leaning out and its not pulling timing

I still cant figure out what could cause a low maf reading without it being the maf itself. Im wondering if its the ECU asking for less of its mechanically choking somewhere.

 

[Alexis27]

Are you on your original fuel pump?

 

[Connor H]

Are you on your original fuel pump?

Im running a sytec pump.

 

[Connor H]

Does anyone think it could be my turbo? I make 24psi when cool but the power delivery is so flat, doesnt throw you back in the seat, and is slow to build back up after shifting.

The other thing to mention even on a 23c day of town driving the car gets stuck at 5psi and stays that way until a long drive cools it down. Im thinking its heat related but everything in the ecu is reading correctly, so maybe the turbo/wastegate/actuator getting hot for some reason?

might explain the low air flow the maf is seeing...

 

[Alexis27]

Sorry if you've already tried this, but a sticking N75 valve will cap the turbo at 5psi.

 

[Connor H]

Sorry if you've already tried this, but a sticking N75 valve will cap the turbo at 5psi.

I will try borrow my mates n75 and see if it changes anything. Mines only a few years old from the stealers so i hope its not that lol. I think at this point ive swapped/replaced most sensor parts except the throttle body and n75.

 

[Connor H]

Necro my own thread because this issue is still going on and amongst poor health i havnt had much time to focus on it.

Ive since had the car re-tuned by tuning technics and it did not fix the issue. The car wasnt completely responding as it should have so just did a safe tune.

It was okay for a couple of weeks then it just went flat again. Replaced the MAF twice, Is okay for a couple of weeks then same. just finished replacing the turbo, no change.

After a lot of sensor checking in VCDS ive ruled it out down to these symptoms:

poor data from the maf wiring, or something wrong with the VVT unit i replaced AGES ago.

No codes
Maf wont break 150 - 160gs (meant to be running 230hp)
VVT is NOT turning on during driving, output tests say its functional - it does turn on for the cold start conditions. The VVT solenoid is leaking oil though. and according to google that can cause its functionality to fail.

Anyone want to weigh in on this? Because im baffled.

 

[Alexis27]

Well the other side of the coin when it comes to air and pressure is the map sensor. If you don't mind firing up the parts cannon, at least it's only £25

https://ebay.us/m/RVgkQM

 

[Connor H]

Well the other side of the coin when it comes to air and pressure is the map sensor.

During this time my old map sensor got wet and shorted, so i have also replaced that too...

 

[Connor H]

Not much to update. Thrown time and money at it some more...

Changed turbo. Changed intake.
Another new MAF and replaced the VVT solenoid with a genuine one, sorted out the O ring inside to stop it leaking.

Still not fixed the issue. Have narrowed it down to the cams not advancing between 1800-4k ish. Only thing i can find. People have tried to tell me that VVT only works on idle or on a bam engine. According to manufacturer data and Nefmoto, the VVt does indeed advance the cams on AUQ models, and it makes sense because thats where ive lost my power and the turbo is laggy.

So if anyone out there that has VCDS and feels like helping me keep my sanity, please log block 91 for me and check the cam advancing lol

Otherwise this car is going to the scrap pretty soon.

 

[mty12345]

Hey mate.

AFAIK the VVT only advances during warm-up. I'm 99% sure it does nothing at any other time. Happy to log block 91 and confirm on my AUQ for you though. I'll try and do it in the next couple of days.

What exactly are the symptoms of the power loss when it happens? I re-read your first post but those logs all looked ok to me.

 

[Connor H]

Hey mate.

AFAIK the VVT only advances during warm-up. I'm 99% sure it does nothing at any other time. Happy to log block 91 and confirm on my AUQ for you though. I'll try and do it in the next couple of days.

What exactly are the symptoms of the power loss when it happens? I re-read your first post but those logs all looked ok to me.

If you could log it ill send you beer money! I have no other way of confirming this and its my last idea to try before scrapping it

issue is between 1.5k and 4-5k the power is flat and delayed, the turbo spools to the moon. but the car takes at least 2 full seconds before even starts to move. Even the tuner noticed it.

more noticeable when banging through gears - floor it - shift - there is again a solid 2 second delay before the power comes back in even though its maxing out on boost.

It used to be instant power when in the power band as any other 18t is, torque steer etc.

Tbh i thought when the issue began the airflow sounded different and kind of thin. Thats why i changed my turbo and intake to rule out any pipe collapses etc.

My thinking was if the valves are closed at the wrong point the air is getting backed up and wont flow through properly. I even checked my Cat wasnt melted.

The other main symtpoms is the car keeps adapting to low airflow (150gs), im on my 4th(?) MAF now and they read 190+gs, then it slowly drifts back down to a flat and gutless 150gs . of which irun the maf unplugged cos it runs better.


Edit: when i log 91, advance stays OFF and the angle goes to -1 (from 0.0) I believe it has to be over 85% load to activate.

 

[mty12345]

If you could log it ill send you beer money! I have no other way of confirming this and its my last idea to try before scrapping it

issue is between 1.5k and 4-5k the power is flat and delayed, the turbo spools to the moon. but the car takes at least 2 full seconds before even starts to move. Even the tuner noticed it.

more noticeable when banging through gears - floor it - shift - there is again a solid 2 second delay before the power comes back in even though its maxing out on boost.

It used to be instant power when in the power band as any other 18t is, torque steer etc.

Tbh i thought when the issue began the airflow sounded different and kind of thin. Thats why i changed my turbo and intake to rule out any pipe collapses etc.

My thinking was if the valves are closed at the wrong point the air is getting backed up and wont flow through properly. I even checked my Cat wasnt melted.

The other main symtpoms is the car keeps adapting to low airflow (150gs), im on my 4th(?) MAF now and they read 190+gs, then it slowly drifts back down to a flat and gutless 150gs . of which irun the maf unplugged cos it runs better.


Edit: when i log 91, advance stays OFF and the angle goes to -1 (from 0.0) I believe it has to be over 85% load to activate.

Appreciate the offer mate, but no need for beer money. I'll take my laptop to work with me tomorrow and i'll do a couple of logs on my way home.

Weird symptoms, not surprised you're fed up with it. Can't really think of anything else that you may have missed.

 

[Connor H]

Appreciate the offer mate, but no need for beer money. I'll take my laptop to work with me tomorrow and i'll do a couple of logs on my way home.

Weird symptoms, not surprised you're fed up with it. Can't really think of anything else that you may have missed.

Yeah mate completely fed up, so this is very much appreciated.

 

[ExiledWeegie]

only things i could think of might be the throttlebody, intake air temp sensor, n75 or the fuel pump not being able to keep up with airflow, you mentioned the trims as 9.4% long term, thats a bit lean so could be fueling related?

 

[Connor H]

only things i could think of might be the throttlebody, intake air temp sensor, n75 or the fuel pump not being able to keep up with airflow, you mentioned the trims as 9.4% long term, thats a bit lean so could be fueling related?

last time i looked month or two ago the fuel trims were well within spec. If anything its running rich because the fuelling is for more power, probably why it runs better with the maf unplugged.

TB has been reset and replaced with a used but good genuine one, logged, all good.

the tuner looked over the essentials like fuel , timing etc when he mapped it. He saw nothing wrong.

Literally a phantom issue. Ill probably get a compression check to make sure its not got a bent rod or something

 

[ExiledWeegie]

so is the 9.4% actually -9.4%? minus fuel trims means rich, positive means lean. does it have standard auq injectors in it? it be doubtfull its a bent rod if the car feels fine for a while on a new maf but then starts tailing off again over a week or two.

when i got my auq stage 2 i noticed that it was overfueling upto and around -12% ltft, so i bought a mpps cable, downloaded the map and edited the krkte to scale the bam injectors that id installed back down so that it was closer to 0.0%, it made a big difference in how the car drove, was much more responsive on the throttle since the ecu wasnt having to pull as much fuel back. although this doesnt sound like your problem i dont think.