Audi A3 1.8t engine cutting out intermittently

[Mark Rosewell]

Hi all

I have just bought an Audi A3 1.8t (2001)
It's got 131000 miles on the clock. Was running fine until I gave it a good throttling and the engine seemed to cut out. I let the revs come down, slowly put my foot on the gas, then it came back and ran fine.
The next day I had the following engine codes p0420 & (p0011 pending) i topped up the oil which was low and erased the codes then I got p0102. I cleaned the filter and Maf, erased the code and have done aprx 100 miles with no codes though the problem with the engine cutting while boosting is still very much a problem.

Any hints as to what it is? Happy to answer any questions.

Cheers

 

[<tuffty/>]

http://wiki.ross-tech.com/wiki/index.php/16804/P0420/001056
16804/P0420/001056 - Catalyst System; Bank 1: Efficiency Below Threshold

http://wiki.ross-tech.com/wiki/index.php/16395/P0011/000017
16395/P0011/000017 - Bank 1: Camshaft A (Intake): ****** Setpoint not Reached (Over-Advanced)

http://wiki.ross-tech.com/wiki/index.php/16486/P0102/000258
16486/P0102/000258 - Mass Air Flow Sensor (MAF/G70): Signal too Low

MAF needs replacing

<tuffty/>

 

[Mark Rosewell]

http://wiki.ross-tech.com/wiki/index.php/16804/P0420/001056
16804/P0420/001056 - Catalyst System; Bank 1: Efficiency Below Threshold

http://wiki.ross-tech.com/wiki/index.php/16395/P0011/000017
16395/P0011/000017 - Bank 1: Camshaft A (Intake): ****** Setpoint not Reached (Over-Advanced)

http://wiki.ross-tech.com/wiki/index.php/16486/P0102/000258
16486/P0102/000258 - Mass Air Flow Sensor (MAF/G70): Signal too Low

MAF needs replacing

<tuffty/>

So would the Maf be causing the engine cut out problem you think?
Would be great if it is as it's an easy fix.
Also it feels a bit laggy at times, then suddenly fine.

 

[<tuffty/>]

Yeah... MAF is a key component in the efficient running of the engine... unplug it as a test... it should run better... they are realistically a service part anyway so get yourself a new one... make sure its a genuine Bosch sensor so either one from GSF or a dealer

<tuffty/>

 

[Mark Rosewell]

Yeah... MAF is a key component in the efficient running of the engine... unplug it as a test... it should run better... they are realistically a service part anyway so get yourself a new one... make sure its a genuine Bosch sensor so either one from GSF or a dealer

<tuffty/>

Ok thanks I'll try it out and keep you updated

 

[Mark Rosewell]

Yeah... MAF is a key component in the efficient running of the engine... unplug it as a test... it should run better... they are realistically a service part anyway so get yourself a new one... make sure its a genuine Bosch sensor so either one from GSF or a dealer

<tuffty/>

Ok so I just took it for a run without the Maf plugged in and it did run fine when really giving it a boot. Although, it always ran fine until it'd randomly cut out so hard to tell if it's worked for sure. Would it be bad for the engine if I left the Maf unplugged for a day? Also the traction control switched off, don't know how that's related to the Maf.

 

[<tuffty/>]

Traction control is tied to the maf as the ecu controls the engine to control traction... the maf is used to measure load so once unplugged the ecu can't see airflow so has no way to gauge load accurately rendering traction control unpredictable... So it gets disabled...

You can drive with the maf disconnected but get it sorted sooner rather than later

<tuffty/>

 

[Mark Rosewell]

Traction control is tied to the maf as the ecu controls the engine to control traction... the maf is used to measure load so once unplugged the ecu can't see airflow so has no way to gauge load accurately rendering traction control unpredictable... So it gets disabled...

You can drive with the maf disconnected but get it sorted sooner rather than later

<tuffty/>

Right I'm now thoroughly perplexed.
The p0102 code came back with the maf disconnected which is understandable as its reading there is nothing there. But now I have a new pending code p0303 - cylinder 3 misfire detected. I've plugged the maf back in and am ordering a new Bosch maf to come. But I am concerned that there is a much bigger problem with this vehicle that's waiting to happen.

I've attached an image of the freeze frame data taken at the time the p0102 fault was detected. Does this seem normal?

 

[<tuffty/>]

all related I suspect... misfire maybe because the ECU is best guessing fuelling (and correcting after the fact using the wideband lambda) as it can't see load... uses expected airflow over throttle plate calculations to determine injector duty... this can be an issue if the car is tunes or has any form of mod on it as airflow can be more or less depending on mods... this can also be more problematic on cold start too when lambda control is switched off while lambda heating is getting up to temp...

MAF is faulty, thats a given... once thats replaced reset codes, let ECU adapt fuel trims and go from there... can't diagnose easily while you have known faults

<tuffty/>

 

[Mark Rosewell]

all related I suspect... misfire maybe because the ECU is best guessing fuelling (and correcting after the fact using the wideband lambda) as it can't see load... uses expected airflow over throttle plate calculations to determine injector duty... this can be an issue if the car is tunes or has any form of mod on it as airflow can be more or less depending on mods... this can also be more problematic on cold start too when lambda control is switched off while lambda heating is getting up to temp...

MAF is faulty, thats a given... once thats replaced reset codes, let ECU adapt fuel trims and go from there... can't diagnose easily while you have known faults

<tuffty/>

Ok, thank you for your help I appreciate it. The part is arriving on the 9th, I will fit it, reset the codes, and see how it all goes.

Thanks again

 

[michael A]

My car does the same mine is a 1.8 t also 2000 plate this is really useful.
I was told to take off the boost controller as apparantly they are not much good. I think i will too try the MAF.
My car cuts out if i hit boost and let revs drop it cuts out sounds like we have the same issue. I will follow this and please do let me know if it fixes your problem and i shall know then what to do. Great post very helpful info cheers

 

[Mark Rosewell]

Hi guys

Once I removed the old Maf sensor I found that one of the vents had been sucked off half way down the pipe so definitely needed changing. However I'm still having weird lagging problems with the turbo, no engine lights yet but I will update as soon as one appears.
I haven't yet had a problem with the engine cutting out which is a good sign but I am not entirely convinced that the Maf sensor was the only problem.

I will update you with anything new.

 

[Stuart B]

has the ECU learnt the bad readings the MAF was sending and needs resetting? or is that all old wives tales?

 

[michael A]

Ive been told boost controller can efect boosting having mine removed at weekend to see if helps aswell as a few old pipes then im doing maf too i think as not a big job so worth changing the engine seems fine but the lagging and cut outs are annoying i deffo think we have the same problem

 

[Stuart B]

have you got Android Torque and a Bluetooth ODB2 reader that will tell you the boost pressure and when it is spooling up. what are you replacing the N75 EBC with? I have just added mine back because the previous owner put in an MBC instead of using the Audi N75?

you can test it by removing the plug.

could it be the dump valve or a leaky Turbo Intake Pipe or vacuum hose from under the inlet manifold onto the top of the DV, or a charge pipe leak? there are so many different possibilities - sometime mine feels like it is going to cut out, I think that is the exhaust is blowing.

 

[michael A]

So quick update took off my MBC gone back to standar also fixed a leaky boost pipe car is so much nicer still has cut out just the once but we do know of another leak which will be fixed in a weeks time. Sad to say feels slow again as standard however power comes in time. Now its all pretty much back to normal or will be in a weeks time i can start getting ready to add power again but this time do it right. M car was owned by a few lets say chav type guys who did alot of bodge jobs which ive now fixed so next plan is front mount before going in for remapping properly this time.

Thanks to everyone in this post really did help me fix my issues i was having and although still not perfect it is soooo much better and feels good again

 

[Mark Rosewell]

Hi guys

Another update. I am now experience a huge loss in power, expected n75 or boost leak somewhere not too sure. The car is still under warranty for another week so I am having it diagnosed hopefully tomorrow.
I've also noticed a rattling sound coming from the engine between 1 and 2.75 rpm. And a huge downfall in mileage per gallon. Anyone got any tips that I can pass on to the garage?

Thanks.

 

[<tuffty/>]

Scan for fault codes and post them up... can assist better then...

I'd also be tempted to take it to a specialist rather than a n other garage.... mainly because a specialist is more likely to be familiar with the engine

<tuffty/>

 

[Mark Rosewell]

Scan for fault codes and post them up... can assist better then...

I'd also be tempted to take it to a specialist rather than a n other garage.... mainly because a specialist is more likely to be familiar with the engine

<tuffty/>

I'll do a scan now and see what comes up.
I need to go through the warranty to have it scanned and worked on at the moment. if they can't help for free I'll be going straight to a specialist.

 

[Mark Rosewell]

Scan for fault codes and post them up... can assist better then...

I'd also be tempted to take it to a specialist rather than a n other garage.... mainly because a specialist is more likely to be familiar with the engine

<tuffty/>

I've just run a scan and there's nothing to report. Seems to be running fine again annoyingly, these intermittent faults are a real pain. I'll see what I can get done through the warranty then take it to a specialist if nothing comes up. Thanks again will keep you posted.

 

[<tuffty/>]

If losing boost intermittently then chances are its hitting limp mode for some reason...

Did you use VCDS to do the scan?

<tuffty/>

 

[Mark Rosewell]

If losing boost intermittently then chances are its hitting limp mode for some reason...

Did you use VCDS to do the scan?

<tuffty/>

Forgive me I'm not sure what VCDS is. I only have a £15 scanner program on my laptop. I can view and erase codes and view live data on a few parts of the car like fuel trim etc. It's nothing amazing.
i read if the n75 is faulty then the car will go into limp mode. But would that explain the extra fuel consumption? Even though I'm not driving with a heavy foot.

 

[<tuffty/>]

VCDS (formally VAGCOM) is the defacto software used for VAG car diagnostics... VAG extend the OBDII fault code set to give more granular info regarding a fault and more generic software can miss these codes...

If you already have an OBD lead for your laptop then you should try using VCDS lite... this is the free version with limited functionality but will read all VAG fault codes... VCDS lite won't give all the descriptions but you can look the codes up here to get the descriptions...
http://wiki.ross-tech.com/wiki/index.php/Category:Fault_Codes

VCDS lite can be downloaded from here
http://www.ross-tech.com/vcds-lite/download/index.php

<tuffty/>

 

[Mark Rosewell]

VCDS (formally VAGCOM) is the defacto software used for VAG car diagnostics... VAG extend the OBDII fault code set to give more granular info regarding a fault and more generic software can miss these codes...

If you already have an OBD lead for your laptop then you should try using VCDS lite... this is the free version with limited functionality but will read all VAG fault codes... VCDS lite won't give all the descriptions but you can look the codes up here to get the descriptions...
http://wiki.ross-tech.com/wiki/index.php/Category:Fault_Codes

VCDS lite can be downloaded from here
http://www.ross-tech.com/vcds-lite/download/index.php

<tuffty/>

I've downloaded it but I need to purchase their scan tool to use it.
I've just done another scan with my current program and got two pending codes p0300 - random/multiple cylinder misfire detected and p0303 - cylinder 3 misfire detected. Any thoughts?

 

[<tuffty/>]

You can use VCDS lite freely with any ebay or third party lead... make sure you have downloaded the right version...

Those codes are likely to be symptomatic of the issue in hand... chances are there is something causing the fuelling to run rich (or even lean)... have you changed the MAF sensor yet?

Smoke test is worth getting down to check for leaks... if your current software can check for fuel trims then maybe worth checking those to see where they are... unfortunately VCDS lite won't show blocks above 25 so you can't see fuel trims (block 032) in that without registering it

<tuffty/>

 

[Mark Rosewell]

You can use VCDS lite freely with any ebay or third party lead... make sure you have downloaded the right version...

Those codes are likely to be symptomatic of the issue in hand... chances are there is something causing the fuelling to run rich (or even lean)... have you changed the MAF sensor yet?

Smoke test is worth getting down to check for leaks... if your current software can check for fuel trims then maybe worth checking those to see where they are... unfortunately VCDS lite won't show blocks above 25 so you can't see fuel trims (block 032) in that without registering it

<tuffty/>

Ok I'll see what I can do with the lead I've got.

My current software can check fuel trims but what am I looking for?
I am having a full scan at the garage tomorrow now, hopefully the diagnostic they give can shed a little more light on the problem.

Yes I have changed the MAF sensor, one of the vents from the old sensor had been sucked into the intake so definitely needed changing.

 

[michael A]

How did you get on at the garage ?

 

[Mark Rosewell]

I went to the garage last Thursday, had the codes reset (as there were too many to see what the real problem was) and was told to come back in a couple days. So today I went and I got these codes
P0420 catalyst system bank 1. Efficiency below threshold.
P0116 engine coolant temp. Circ. Range performance problem.
P1297 connection charger-throttle valve. Pressure drop.

I am waiting to hear back from the guy I bought the Audi off to see if he's actually going to stick to his word and get it fixed.

I am convinced there is an air leak somewhere, I want to do my own smoke test but can't find an efficient way to do so.

 

[michael A]

im sure someone on here could help in regards to smoke test. i have mine going in for a remap in january as i now have my front mount to be fitted first the remap im looking at is with r-tech and includes diagnosis and smoke test. although its not cheap i feel ill be killing a few birds with one stone.
keep us posted on the progress as ive found this thread helpful and im sure others will too

 

[Mark Rosewell]

I got my car back from the garage today.
I've had the cam belt tensioner and cam belt itself replaced as the tensioner was so loose I could hear it rattling and it was also effecting the engine idle. The thermostat and sensor were also replaced. This has definitely improved the vehicle running but still no luck with the slight lag under boost. They didn't perform any further tests for leaks etc as they feel the car is driving fine now where as me who drives it every day can tell its still not quite there yet. I've got to get some more money together before I can get anything else done now but I will update the thread as I go along.

 

[badger5]

smoke leak tests are standard first job on everything we see in for mapping
Beware of some outfits not expecting a "problem car" to arrive for mapping, where they have several others booked in the same day, you might not get you car fixed or mapped if time pressures prevail

 

[Mark Rosewell]

p0420 code is back again. Weirdly though the car is running well, I guess the ECU has sorted itself out with the thermostat now giving correct readings?.....
This code seems to be very common with these engines, and no one so far has found a 'one fix' solution to the problem.
I'm going to do more research on it.

As for the original problem with the engine cutting out under boost, I am fairly confident that the faulty MAF sensor was causing the problem. I have not had any issues in that respect since having the sensor replaced. If anyone's having a similar issue I would start there, it's cheap and very easy to replace yourself.