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Author Topic: Loss of power  (Read 3226 times)

Offline AlexRennieGti

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Loss of power
« on: March 01, 2019, 06:21:49 pm »
Hi guys looking for some help with a weird fault.
I have a mk5 gti with 2.0tfsi engine. I was driving along motorway yesterday and car lost power. Engine won’t rev passed 4000 rpm. Car struggles too pull to any speed. Also car struggles too start. Had a garage scan it today no fault codes showing up at all.

Any suggestions what I should look at next ?

Thanks


Offline muff1991

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Re: Loss of power
« Reply #1 on: March 02, 2019, 12:05:13 pm »
Are you only having trouble starting in the colder weather? I’m having power cuts at 4K too and also cold start issues, when freezing it starts but cuts out, when milder it starts but laggy throttle.
@pudding has been helping me out with this issue, and I think it’s come to the conclusion it could be fuel cuts (maybe a tired hpfp) and an air leak or some other electrical issue for the cold starts. I also have no codes flagging up! But issue sounds very similar... let me know if you find a fix, and/or I’ll let you know too!


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Offline Pudding

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Re: Loss of power
« Reply #2 on: March 04, 2019, 12:28:47 pm »
High pressure fuel pump I reckon.  You won't always get a fault code for that unless it fails to meet the required pressure for a set period / rpm window.   But that's what a lot of garages do isn't it.  No codes, send you on your way.  Was deeper analysis not offered?  Such as a road test with sensor logging?

Critical sensors like cam, crank, throttle and pedal are fault coded.  Emissions related faults such as lambda, cat efficiency etc throw a CEL.  There are a lot of items that aren't fault coded, so more investigation is required.


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Offline AlexRennieGti

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Re: Loss of power
« Reply #3 on: March 07, 2019, 08:19:25 am »
I have replaced my Hpfp and have regained most of my power but now if I push the car at 90-100mph the power is dropping away again. Put foot down and nothing. Think maybe need upgraded Hpfp as standard one not supplying enough fuel.

Thoughts?

Offline Pudding

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Re: Loss of power
« Reply #4 on: March 08, 2019, 09:52:52 am »
It won't hurt to add VIS internals but if it's standard, it shouldn't be doing that.  Time for some data logging of the boost and fuel rail channels I think.


2007 ED30 | Ohlins Coilovers | Revo Map | Plus some other stuff | Is all a GTI needs :-)

Offline AlexRennieGti

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Re: Loss of power
« Reply #5 on: March 14, 2019, 09:55:52 am »
Thought I had this issue fixed but not sure if it’s back or this is a different one now. Driving the car yesterday and was running fine then power went very flat as if no boost pressure. The power came back after a minute or 2. Went home all was fine. Came back out this morning car ran ok first 5 min then flat again. Turning the engine off and back on seems too make the power return as if it’s resetting something. Could this be caused by a bad dv ?

Offline Chesto18

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Re: Loss of power
« Reply #6 on: March 14, 2019, 12:50:51 pm »
Thought I had this issue fixed but not sure if it’s back or this is a different one now. Driving the car yesterday and was running fine then power went very flat as if no boost pressure. The power came back after a minute or 2. Went home all was fine. Came back out this morning car ran ok first 5 min then flat again. Turning the engine off and back on seems too make the power return as if it’s resetting something. Could this be caused by a bad dv ?

Doesn’t sound like the DV. They tear causing a permanent boost leak. Turning off/on won’t affect it.

TBH it sounds similar to an issue I had with an A3 many years ago and I believe is turbo related. The car would lose power out of nowhere, as if it had lost all boost pressure. A quick turn off and restart and it would be back to normal. No engine fault light either.  If so it sounds as if your car is cutting the boost pressure. I’m not sure why this would be, but someone will be along to help. Hopefully it’s just a dodgy sensor somewhere.

Offline dazza

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Re: Loss of power
« Reply #7 on: March 14, 2019, 01:01:07 pm »
Sounds like its going into limp mode. My alhambra does this and only restarting the engine resets it. It goes into limp mode to protect the engine. The error i get is turbo overboost.

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Offline muff1991

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Re: Loss of power
« Reply #8 on: March 14, 2019, 01:46:45 pm »
It might be worth chucking a new crank sensor in.. even if it’s just a Euro car parts one. They’re only £13


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Offline Pudding

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Re: Loss of power
« Reply #9 on: March 14, 2019, 02:33:33 pm »
Mine's been like that for years.  It can be really good for days and really flat and unresponsive for days, but stopping at the shops restores the power again.

No fault codes, everything logged, nothing out of the ordinary.  Beats me.

My tuner mentioned years ago he'd upload a map to a customers car, and then a few weeks later they'd ring back saying it's lost all it's performance.  He's also mentioned in the past about Revo maps leaving footprints in the ECU you can't get rid of when overwritten with a new map.  Maybe there's a correlation there.  Either way, the ECU is adapting down. Possibly because the 'driver demand' torque strategy it uses is confused by the requested boost and HPFP numbers of a remap.  Not sure!

Welcome to the inconsistent world of VW turbo engines.


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Offline AlexRennieGti

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Re: Loss of power
« Reply #10 on: March 14, 2019, 02:37:32 pm »
There are times the power kicks back in itself. Its not showing up any faults either.

Offline AlexRennieGti

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Re: Loss of power
« Reply #11 on: March 14, 2019, 02:40:04 pm »
Mine's been like that for years.  It can be really good for days and really flat and unresponsive for days, but stopping at the shops restores the power again.

No fault codes, everything logged, nothing out of the ordinary.  Beats me.

My tuner mentioned years ago he'd upload a map to a customers car, and then a few weeks later they'd ring back saying it's lost all it's performance.  He's also mentioned in the past about Revo maps leaving footprints in the ECU you can't get rid of when overwritten with a new map.  Maybe there's a correlation there.  Either way, the ECU is adapting down. Possibly because the 'driver demand' torque strategy it uses is confused by the requested boost and HPFP numbers of a remap.  Not sure!

Welcome to the inconsistent world of VW turbo engines.


Your right it can have days even weeks of running perfect and then boom no power

Offline Pudding

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Re: Loss of power
« Reply #12 on: March 14, 2019, 03:12:09 pm »
With my ED30, it feels like all the power moves to the top end.  On a good day there's responsive torque everywhere, even off boost.  On a bad day, it can't pull the skin off a rice pudding below 3000rpm and feels really heavy and reluctant to get moving.

I've checked everything.  Binding brakes, flat tyres, boost leaks, PCV, DV, data logging.....everything.   

A new ECU that's never been flashed is my next port of call, but the faff of coding my key to it is putting me off.

One thing I and Muff1991 have noticed is the performance improves as the weather gets warmer!  Should be the other way round with turbo engines  :grin:
« Last Edit: March 14, 2019, 03:14:25 pm by Pudding »


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Offline AlexRennieGti

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Re: Loss of power
« Reply #13 on: March 14, 2019, 05:42:42 pm »
Well guys driving home from work and power goes flat again. If I press accelerator on and off a few times power comes back briefly then disappears again.

Feel like just finding a big wall and crashing into it 😂😂

Offline muff1991

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Re: Loss of power
« Reply #14 on: March 14, 2019, 07:10:16 pm »
Alexrennie... is your car going flat at a certain point (rpm)? are you describing flat spots when pressing on or car just feels dead and laggy?

As pudding said, I have been chasing an issue with mine since November time! But unfortunately it’s only weather related so really hard to have the weather on a day and convenient time I can diagnose.

Mine started here:
We had a low (above freezing) morning and I started the car... idle dropped a lot quicker than normal.. and as I throttled to go I noticed the throttle was LAAGGGYY as hell.
Might be worth reading my cost start issue post for full detail.
But it was basically laggy up to 2k rpm and above seemed more normal.
Then even know engines fully up to temp, the car still drove like this!
When I booted it... it would reach 4K rpm and litterally CUT the power as if someone turned the boost off!! The DV psshhh can be heard and although I keep it pinned it can take a good few seconds which feel forever and then the power kicks back in like someone’s just give back all the boost it’s lost  ALL in one go!

After all that above started I noticed this...
As soon as the outside temperature is below 0 degrees the car starts on the button and the revs just die down and cuts out! Start it back up.. dies!
Even tried throttling to keep the engine running... but the pedal didn’t do NOTHING! Beats me mate! Done Throttle body, all the usual stuff.. logged all I know. And still no where!

My little experiment:
I took the ECU out the car today and wacked it in the freezer for 5 hours, plugged it back into the car and started it.. didn’t make any difference! I thought by freezing it would create below 0 for the ECU so that eliminates my theory of the ECU playing up when freezing! It’s something telling the ECU to draw back or the ecu is faulty and/or it’s the software!

I am going to send my ECU off to be tested and then if no difference I’ll be having a standard map put back on the car! Or as per puddings idea, grab a second hand ECU but will need to speak to some matey that has access to the Immobilizer, key coding and all that rubbish.

Throw around any ideas or more info. We gotta get to the bottom of all this! I’m certain your problem is the same if not very similar and on the same lines as mine!





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