Mk5 golf gti tfsi hesitation

[Mackenzie79]

I've only had it a few months and had to issue from day one and it hasn't got worse. It only happens under load from cold start and it's very brief. It runs perfectly after with no stutters or misfires. I'm gonna get it motd Monday and if all is well get the oil changed, change the dv and clean the turbo. Hopefully this will help. My local mechanic doesn't see it as a huge issue and says I should just live with it as it drives perfectly besides this initial fault. Unless it's a bearing cleaning the turbo will hopefully help.
I've read a few comments about the warm up routine, some have said the issues I'm having are normal?! It's does as you say slam down the power sometimes but only very briefly. It feels like the exhaust is blocked and then is ok. The car is 55plate and don't think its worth changing the turbo. Personally think the issue would still be there especially if they do suffer bad starts anyway.

[pudding]

You can't really clean a turbo unless it's dismantled.  All you can do is squirt some carb cleaner into the compressor housing to remove PCV gunk, but that doesn't achieve anything anyway as the turbo is designed to run like that.  They are pretty much sealed units and designed to replaced as a job lot.

The cold start flatness just feels like it's down about 50hp, but still perfectly smooth and drivable. As soon as the closed loop fuel control kicks in (40 deg water temp) it's got full power.  That is what's normal.  The momentary loss of power that you describe isn't though!  Does it feel like a fuel cut, or throttle closure?  The ECU can close the throttle independently of pedal position if it's not happy with something.

How many miles on it?  If the turbo is still going strong well past 110-120K miles, it's obviously been looked after and will carry on going strong if maintained well.  Abused/neglected cars are usually lucky to see 90-100K from a turbo.

[Mackenzie79]

The car has 118000 miles and has full service history. It came with lots of receipts and was advertised as having a  full engine rebuild and stage 1 remap. When it's been hooked up no one has mentioned the remap so I'm not entirely sure it is. How would you know as it wasn't mentioned when on vagcom? Visually is immaculate inside and out.
It feels like a fuel cut but as said very brief and then has full power long before it's reached temp. It happens first thing in the morn and when I leave work in the evening so when it has been left for a while. If I idle until the needle drops and pull away slowly it doesn't happen. If I put my foot down a little it crawls along like it's getting no fuel for 3-4seconds and jumps into life and drives with no issues.
I've seen on YouTube you can buy cans on turbo cleaner that is sprayed into the intake that is supposed to remove gum, carbon ppl have even used Mr muscle oven cleaner (I don't intend on doing that) but with the issue I'm having I don't see using the turbo cleaner will hurt. It may not work but ifs there is a slim chance it could clean possible carbon away its worth a shot. My local mechanic said he would clean it next week after mot but not sure how.

[muff1991]

The Mr muscle trick, is usually used for cleaning a diesel Variable Vein Turbo (someone correct me if i'm wrong). Some form of cleaner sprayed into the intake may help clear some of the oil residue inside the cold side of the turbo (compressor) but it'll more than likely gather again soon after but i guess it wouldn't hurt to try.

My hesitation, cold start issues etc etc is for sure closing the throttle plate. having no throttle is causing my hesitation! i have seen it on VCDS: Throttle pedal = maxed out! and Throttle plate = 30% (for example) remember i was banging on about the Intake Air Temperature sensor.. well if i disconnect this, i get full throttle function at both ends! its worse for me the colder it is, anything under minus the car starts, idles for like 10 seconds and then just stalls, if i try throttling it doesn't even work at all loool I've got to figure what the hell is retarding the system and closing the throttle plate!

You can look at the flash status on VCDS to see how many "flashes" the ECU has had by going into Engine, Advanced ID and scrolling down to flash attempts. mine has had 4 so maybe 1 or 2 for VW updates or whatever, and 1 or 2 for mapping i guess! - I learnt this from good old @Pudding  ;-P

You cant buy the actuator from OEM without buying a turbo = big money! But you can buy a new aftermarket actuator from the likes of Forge Motorsport, you'd need to have the Penny Valve checked on the turbo to makes sure it seals ok and nothings broken. i can't see the Actuator sticking when cold tbh but the most weirdest of things can happen! A worn or perished diaphragm inside the Actuator could cause the Actuator not to release the penny valve correctly and cause an Over boost though.

honestly though, please try disconnecting the IAT sensor before you start and drive off as normal.. see if theres any hesitation at all. Just in case you're slowly approaching my territory. Not that i have a solution for you haha.

[Mackenzie79]

I asked my mechanic exactly what he intended to do and he said there was a foam cleaner that is left on for a couple of hours much like the Mr muscle trick but he says it's proper turbo cleaner. I wouldn't know,  but he's got a good rep and think it's definitely worth a shot.

Mot failed, rear spring snapped near the base and on its way the other side. Getting them replaced Thurs so will look into the oil change and turbo clean after. The guy at the lion garage with vagcom definitely said it was sticking at the dv value built into the turbo. I know this is a separate part after reading all the stuff on here.

When he put it on vagcom he called to tell me the faults but said it would cost more to see why the faults were happening and told me as above. Got the feeling he just wanted me to get a new turbo. I asked for a print out and he just gave me a basic reciept with very little info.

As you mentioned I can't see it sticking just when it's cold and for so briefly and then being fine. I will try disconnecting the iat and see what happens. You say it gets worse in the cold? Is this also solved by disconnecting the iat? Is this something you have to do every morning?

[Mackenzie79]

Also I mentioned to the guy at vagcom that these faults didn't show at my local garage. My local garage managed to read live data and diagnosed a temp sensor a few weeks ago so his diagnostics must me reasonable but he just said vagcom was better and prob wouldn't have shown up on my mechanics diagnostics. Does that sound legit?

[muff1991]

Also I mentioned to the guy at vagcom that these faults didn't show at my local garage. My local garage managed to read live data and diagnosed a temp sensor a few weeks ago so his diagnostics must me reasonable but he just said vagcom was better and prob wouldn't have shown up on my mechanics diagnostics. Does that sound legit?

Yes mate, vcds (vagcom) is much better than most generic OBD code readers. How old is the DV? What temp sensor was replaced, as possible the Coolant temp sensor could cause issues. I only drive the car once a week, but if the temps outside are above 10 I get no problem at all with the IAT connected. If the temps are 4 degrees outside I get really laggy throttle and if the temps are below 0 I get stalls etc. Totally undrivable. Then if I disconnect the IAT at those temps the car drives fine like you’ve just flicked a switch. I know by disconnecting it makes the ECU run on a “basic” setting.
If yours is doing it every morning then possibly this might help it might not. Have you tried things like the PCV test etc? You might have a vacuum leak and on warm up the cars having to try and compensate.


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[Mackenzie79]

It was the coolant temp sensor he said it was faulty and reading really high. I assume the dv is as old as the car as its not in any of the receipts although it had a turbo actuator valve in 2014, wasn't sure if this was another name for it?
I had the PCV valve changed a few weeks ago, what's the PCV test? I've changed the plugs, fuel filter and cleaned the iat sensor, maf and map sensors. The idle doesn't flicker and has never stalled yet. Vagcom mentioned a misfire, my mechanics said this could be historic as it doesn't misfire unless they are suggesting my issue is caused by a misfire and a sticky turbo valve? Does my issue sound like a misfire?

[muff1991]

The DV (diverter valve) is separate to the turbo actuator. The DV is a good thing to change for the price, if this hasn’t been done then definitely get it changed over for a revision G.

The misfire could cause it I guess but your mechanic has probably cleared the fault as it could be an old code and wants to see if it comes back, if it comes back then it will indicate you do have a misfire for sure. If you do, it will probably be down to an injector. Or plugs and/or coils, but usually turns out to be an injector. If not then don’t worry about it.

The PCV test is easy, have the engine running on idle and pull the dip stick out if the engine begins to run lumpy and wanting to cut out then you know it’s fine. If it doesn’t change then you have a weak/faulty PCV.


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[muff1991]

apologies, i just remembered you have a new PCV so ignore the test and suggestion.

[bobby_fodge]

I had slightly different symptoms to you. I would get what felt like fuel cuts randomly when accelerating. This had been going on for about a month. The cuts would only last a second, the revs would drop and then the power would return. The two VCDS codes I got were around fuel pressure. In the last 6 months I'd replaced the in tank pump, the in tank pump harness and the fuel filter, after reading the VCDS ouput even though I didn't have any symptoms.

A couple of weeks back I changed the HPFP and still had the issues. I ended up buying a genuine VW in tank fuel pump and that has solved the problem.

 

[muff1991]

I had slightly different symptoms to you. I would get what felt like fuel cuts randomly when accelerating. This had been going on for about a month. The cuts would only last a second, the revs would drop and then the power would return. The two VCDS codes I got were around fuel pressure. In the last 6 months I'd replaced the in tank pump, the in tank pump harness and the fuel filter, after reading the VCDS ouput even though I didn't have any symptoms.

A couple of weeks back I changed the HPFP and still had the issues. I ended up buying a genuine VW in tank fuel pump and that has solved the problem.

Hi @bobby_fodge , funny you should say this. as about a year ago.. i was driving home in the scorching heat and when idling in traffic i heard a whining noise from the rear seat, thought straight away my in tank pump is on the blink, as soon as id rev the whine stopped but return to idle and it was whining. on my next journey the noise had gone, I've never heard it since so never thought any more on it, but its been at the back of my mind for a while as a possible culprit but hard to say its that when the hesitation goes away with the IAT disconnected. What was you looking at on VCDS to indicate a bad fuel pump? i have looked at low fuel pressure, i get around 3.9bar in cold weather and this morning (12 degrees) i was getting 4.8bar everything else seemed to look ok too going by Ross Tech's "fuel pressure testing".

Also @Mackenzie79  did i see you post a reply about DPF cleaner etc? if you did.. its now gone! Or it was on another thread and not this one 

[bobby_fodge]

These are the codes i saw in VCDS

012555 - Low Pressure Fuel regulation
               P310B - 008 - Fuel Pressure Outside Specification
             Freeze Frame:
                    Fault Status: 01101000
                    Fault Priority: 0
                    Fault Frequency: 110
                    Reset counter: 255
                    Mileage: 138671 km
                    Time Indication: 0
                    Date: 2000.00.00
                    Time: 09:17:18

             Freeze Frame:
                    RPM: 1343 /min
                    Load: 14.5 %
                    Speed: 35.0 km/h
                    Temperature: 36.0°C
                    Temperature: 15.0°C
                    Absolute Pres.: 1010.0 mbar
                    Voltage: 14.605 V

004195 - Fuel Pressure Regulation
               P1063 - 002 - Control Range Not Reached - Intermittent
             Freeze Frame:
                    Fault Status: 00100010
                    Fault Priority: 0
                    Fault Frequency: 14
                    Reset counter: 255
                    Mileage: 139640 km
                    Time Indication: 0
                    Date: 2000.00.00
                    Time: 16:37:00

             Freeze Frame:
                    RPM: 1241 /min
                    Load: 69.4 %
                    Speed: 33.0 km/h
                    Temperature: 91.0°C
                    Temperature: 26.0°C
                    Absolute Pres.: 1010.0 mbar
                    Voltage: 14.478 V

Readiness: 0000 0000

The VCDS website expands on them about checking fuel pressure etc, tests which I didn't carry out as I am looking to get mine mapped soon so decided to replace the HPFP with uprated internals as an attempt at a possible fix. I'd need this for stage 2 anyway. As the new HPFP didn't solve my issue and I'd had two new fuel filters in the last 6 months it had to be the in tank pump. I took it to awesome GTI who measured the fuel pressure between the tank and the engine bay with the car on the dyno which confirmed the in tank pump wasn't pushing out the fuel at a high enough pressure.

In tank pump is 200 and somthing quid but super easy to fit, take out the bench seat. 

[muff1991]

thanks Bobby, my only issue is i have no codes popping up at all on VCDS :-(

[pudding]

I've put 2 OEM LPFPs in over 5 years.  They're not the best!  They changed the design because people were getting fuel cuts on long journeys due to the pump overheating.  The fix was to basically remove the lid from the pump housing