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  1. #1
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    A3 1.8T Cold start problems. MAF or Fuel?

    I've recently bought a 200BHP Audi A3. It's a 2001 model, and has a full milltek race exhaust system, K&N air filter, Re-circ valve and a custom remap. Dyno print out is 199.1 BHP.
    My problem is the starting of the car. First thing in morning it is a pain to start and stalls out. Soon as the car is warm it starts first turn of the key. The rest of the day can be problomatic but nothing like when it is first started in the morning.

    My question is, would it be a faulty MAF or could the fuel affect this? I was advised to put in high octane (and instantly forgot), I topped up a tenner 95 ron, but the next day I chucked half tank of BP ultimate 97 ron. So I am yet to start it in the morning and see if it makes a difference, but this afternoon it started first time.
    Is it possible I am getting cold start problems with a lower onctane fuel, or does this sound more MAF related?

    The car is in awesome condition, the previous owner has REALLY looked after it and I intend to do the same. So if it is a MAF I'll go get one and pop it in. This is the 2nd A3 I've owned so I am familiar with most of it.

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  3. #2
    bez101's Avatar
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    it wont be anything to do with the fuel
    your better off geting a scan b4 your chuck money at parts that you may not need

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    I was a bit sceptical, but reading some forums it seems some people were saying higher ron fuel might make it easier to start. I'll get a scan as I know someone with Vag-com and speak to the previous owner as he's quite helpfull. What does a MAF reatail at from Audi, I'm thinking £80-£100 ish?

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    Does it do this on a full tank or with less than half a tank? there can be starting issues with these cars when the fuel levels are low....

    The other thing it could be is a vacuum leak... these tend to play up worse when on cold start....

    As mentioned, a scan for fault codes is top of the list as is a check over the hoses under the inlet manifold...

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    bez101's Avatar
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    not sure of price on the 8L but get oem
    iv run stage 3 2 and 1 on 95 never had a start problem
    if it was MAF you would notice it at tickover hot or cold

  7. #6
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    Quote Originally Posted by Ads_AudiA3 View Post
    I was a bit sceptical, but reading some forums it seems some people were saying higher ron fuel might make it easier to start. I'll get a scan as I know someone with Vag-com and speak to the previous owner as he's quite helpfull. What does a MAF reatail at from Audi, I'm thinking £80-£100 ish?
    £111 from GSF with £40 back for your old unit.

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    Coolant sensor?

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    Quote Originally Posted by aragorn View Post
    Coolant sensor?
    +1. Lazy starter motor?

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    Quote Originally Posted by <tuffty/> View Post
    Does it do this on a full tank or with less than half a tank? there can be starting issues with these cars when the fuel levels are low....

    The other thing it could be is a vacuum leak... these tend to play up worse when on cold start....

    As mentioned, a scan for fault codes is top of the list as is a check over the hoses under the inlet manifold...

    <tuffty/>
    My S3 recently started doing this upon start up... What's the cause? Fuel filter? Injectors or something...

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    It only does it on cold start, when I start the engine at temp it kicks in straight away.
    Tank is about half full, I don't like putting in full tanks as it's too much weight! lol
    Vacum leak could be possible, although would this not cause an under powered engine? Once it's started and going it works fine.
    If it was lazy starter motor then this wouldn't cause the engine to start and then stall again would it? I wouldn't thought once started then the engine should just run.

    My gut feeling is MAF or Coolant Sensor. But can't be sure, and a scan is always best as could save large bills that arn't needed!

  12. #11
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    You're right, didn't read the stalling bit, sorry.

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    Fault code it and see if you get 17705.

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    Quote Originally Posted by beachbuggy View Post
    Fault code it and see if you get 17705.
    What happens if I do :-|

    I have a lead, does the shareware VCDS version read fault codes, or do I need full version?

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    shareware is fine.

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  16. #15
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    Quote Originally Posted by beachbuggy View Post
    Fault code it and see if you get 17705.
    That won't affect starting, cold or warm.

    Does the car warm up correctly to 90 degrees? If so it's more likely the coolant temperature sender IMHO

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    Quote Originally Posted by Byzan Photography View Post
    That won't affect starting, cold or warm.

    Does the car warm up correctly to 90 degrees? If so it's more likely the coolant temperature sender IMHO
    It warms up fine, no problem. Once warm it has PLENTY of power and doesn't feel under powered at all. I googled the 17705 and it doesn't sound too similar tbh(although now looking at silicone hoses), it is literally only once in the morning where it is a PAIN to start and then stalls, starts, drops to low idle, then picks up and is fine.
    I am thinking MAF or Coolant sensor, but less MAF now after that would affect idle hot or cold.
    Does VCDS pick up a fault code of coolant sensor is not working correctly?

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    It should do, it will prob show as implausible signal. Because the bit that tells the ECU what temp the car is at is broken, the ECU won't put the car into cold start mode correctly.

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    Quote Originally Posted by Byzan Photography View Post
    It should do, it will prob show as implausible signal. Because the bit that tells the ECU what temp the car is at is broken, the ECU won't put the car into cold start mode correctly.
    So effectivly the ECU is not telling the engine it is cold, and it is putting the wrong mixture in, hence, when the car gets to 90 degrees it runs perfect (it runs fine earlier but I'm saying 90 degrees for example).

  20. #19
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    Quote Originally Posted by Ads_AudiA3 View Post
    It warms up fine, no problem. Once warm it has PLENTY of power and doesn't feel under powered at all. I googled the 17705 and it doesn't sound too similar tbh(although now looking at silicone hoses), it is literally only once in the morning where it is a PAIN to start and then stalls, starts, drops to low idle, then picks up and is fine.
    I am thinking MAF or Coolant sensor, but less MAF now after that would affect idle hot or cold.
    Does VCDS pick up a fault code of coolant sensor is not working correctly?
    If the CTS has a genuine fault it will be picked up in VCDS.. if the fault is that it is reading incorrectly then it won't throw a fault code... CTS issues are normally obvious as the water temp gauge will give you a clue...

    If the CTS is not working correctly it will not necessarily inhibit cold start as the the ECU sees its cold and does what it normally does...

    Out of interest... does your idle fluctuate at all?

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    Quote Originally Posted by <tuffty/> View Post
    If the CTS has a genuine fault it will be picked up in VCDS.. if the fault is that it is reading incorrectly then it won't throw a fault code... CTS issues are normally obvious as the water temp gauge will give you a clue...

    If the CTS is not working correctly it will not necessarily inhibit cold start as the the ECU sees its cold and does what it normally does...

    Out of interest... does your idle fluctuate at all?

    <tuffty/>

    The idle doesn't fluctuate at all apart from when it is first started but the idle dies and then it stalls. Once started and running, hot or cold the idle is fine.

  22. #21
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    Fuel pump?
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    Got the same problem on mine and VAG-COM says coolant temp sensor implausable signal, will be chaging it on Saturday and hopefully sort thr problem.
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  24. #23
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    Battery? It starts better when the cars warm because the batteries charged?

  25. #24
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    Coolant sensor will start fine when cold but struggle to start when its warm

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    Quote Originally Posted by sportquattro View Post
    Got the same problem on mine and VAG-COM says coolant temp sensor implausable signal, will be chaging it on Saturday and hopefully sort thr problem.
    Can you let me know how it goes? I'm now working until Saturday afternoon so going to pick up a sensor Saturday afternoon and fit it on Sunday.

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    Quote Originally Posted by L33h View Post
    Coolant sensor will start fine when cold but struggle to start when its warm
    not always, it can fail the other way too hence the suggestions

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    Well I was working 8-10:30 tonight, so car was left from 7:30 - 22:30 to cool down, wasn't cold out but still started first time straight away. It also started right up after work today and it was left for 9 hours to cool down then, but this morning, it was a pig to start....lets see what tomorrow brings.... But think I'm just gonna change the CTS as process of elimination.

  29. #28
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    Just to clarify, because it hasn't been mentioned yet.

    The "200bhp" shouldn't even factor into it when diagnosing the problem, it is irrelevant. These engines make 200bhp without even breathing, and will be totally reliable at the figure. Chances are it is one of the things mentioned in this thread.

    It is worth mentioning as well that running high octane fuel DOES have a massive benefit on these cars, especially on a stage two tune (which I assume this is, but on a K03). Personally I would only ever be running on Vpower with a stage 2 car, my own car will misfire and won't build boost on standard fuel, and having tried every fuel commercially available Vpower is what it was mapped for and only Vpower will make it run right.

    My own car will also stall at first start in the morning and evening, I find that holding the key for a few seconds longer helps. I do this out of habit now, but if I don't do it then it will occasionally stall. Not sure why it does it, but it does!
    I quite often say I'm going to do things.

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    Quote Originally Posted by 16Klappe View Post
    Just to clarify, because it hasn't been mentioned yet.

    The "200bhp" shouldn't even factor into it when diagnosing the problem, it is irrelevant. These engines make 200bhp without even breathing, and will be totally reliable at the figure. Chances are it is one of the things mentioned in this thread.

    It is worth mentioning as well that running high octane fuel DOES have a massive benefit on these cars, especially on a stage two tune (which I assume this is, but on a K03). Personally I would only ever be running on Vpower with a stage 2 car, my own car will misfire and won't build boost on standard fuel, and having tried every fuel commercially available Vpower is what it was mapped for and only Vpower will make it run right.

    My own car will also stall at first start in the morning and evening, I find that holding the key for a few seconds longer helps. I do this out of habit now, but if I don't do it then it will occasionally stall. Not sure why it does it, but it does!
    I didn't think 200BHP would be a difference tbh, but thought it added to the thread title and would make people have a look :-). The car I am lead to believe has the K03/S turbo, with the exhaust and a remap. I have a 3 dyno print outs, intial 145 BHP standard, 195 BHP with standard fuel and 199.1 BHP on high octane fuel, this is where the ECU is currently left, so I'm running it on high octane.

    I was looking through paper work and found the MAF was done in 2007. I'm going to give it a scan and see if anything comes up in that first before replacing things, but then I will be doing CST as mentioned before. Hoping that solves the issue.

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    Quote Originally Posted by Ads_AudiA3 View Post
    I didn't think 200BHP would be a difference tbh, but thought it added to the thread title and would make people have a look :-). The car I am lead to believe has the K03/S turbo, with the exhaust and a remap. I have a 3 dyno print outs, intial 145 BHP standard, 195 BHP with standard fuel and 199.1 BHP on high octane fuel, this is where the ECU is currently left, so I'm running it on high octane.

    I was looking through paper work and found the MAF was done in 2007. I'm going to give it a scan and see if anything comes up in that first before replacing things, but then I will be doing CST as mentioned before. Hoping that solves the issue.
    It would be a very poorly K03s to only have 199BHP I'm sorry to say. Unless there is a 3" down pipe and a de-cat the exhaust will have made 0 difference to power, but who did the mapping?

    Being a 2001 it will have an AUM in it, so had the K03s as standard. Doing a fault code read it the first place to start, it's a great bit of kit. One thing which people don't understand with these cars, is they have good and bad days! One day it will be perfect, the next it'll have a problem, then it'll fix itself and be the best car in the world again haha!
    I quite often say I'm going to do things.

    Then never do them.

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    Quote Originally Posted by 16Klappe View Post
    It would be a very poorly K03s to only have 199BHP I'm sorry to say. Unless there is a 3" down pipe and a de-cat the exhaust will have made 0 difference to power, but who did the mapping?

    Being a 2001 it will have an AUM in it, so had the K03s as standard. Doing a fault code read it the first place to start, it's a great bit of kit. One thing which people don't understand with these cars, is they have good and bad days! One day it will be perfect, the next it'll have a problem, then it'll fix itself and be the best car in the world again haha!
    It was a company called JKM, local tuners here on the south coast.

    Ok, so I got carried away and am now sat in my car at 00:28 at night doing diagnostics.
    Scan is as follows

    VCDS-Lite Version: Release 1.1
    Friday, 24 February 2012, 00:26:58.


    Chassis Type: 8L - Audi A3/S3
    Scan: 01,02,03,08,15,16,17,22,35,37,45,55,56,57,75,76

    -------------------------------------------------------------------------------
    Address 01: Engine Labels: 06A-906-032-AUM.LBL
    Controller: 06A 906 032 HJ
    Component: 1.8L R4/5VT 0002
    Coding: 11500
    Shop #: WSC 79152
    VCID: 6DAD4AB7349F
    WAUZZZ8LX21001537 AUZ7Z0A1883166
    1 Fault Found:
    16795 - Secondary Air Injection System: Incorrect Flow Detected
    P0411 - 35-10 - - - Intermittent
    Readiness: 0000 0000

    -------------------------------------------------------------------------------
    Address 03: ABS Brakes Labels: Redir Fail!
    Controller: 1C0 907 379 E
    Component: ESP FRONT MK60 0104
    Coding: 0019970
    Shop #: WSC 01236
    VCID: 2C2B87B3CF05
    No fault code found.

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    I have an identical problem on my s3, first start coughs and splutters then runs fine, changed plugs which didn't fix it. All subsequent starts when warm are fine, if anyone figures it out top stuff-cts seems to be the consensus though?

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    Looking at your faults, the ECU doesnt think theres anything wrong.

    That doesnt mean its NOT a sensor though, as a sensor would only log a fault if its output is out of range. If its within normal range but simply wrong, the ECU will believe it.

    I'd start by sticking a CTS in, as they're cheap enough to take a chance on.

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  35. #34
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    Seeing as you have an SAI fault and SAI kicks in on initial start I would say that its a plausible cause of your issue... as this isn't required when warm...

    16795/P0411/001041 - Ross-Tech Wiki

    The SAI uses a vacuum feed so if this is compromised then it may throw this fault and may well be the cause of the stall...

    I would be checking this out first before throwing any more parts at it...

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    Ok, cleared the results and started again, this time I'm getting these results, apologies for not understand all the results but I don't think I'm missing anything blinding obvious here...

    VCDS-Lite Version: Release 1.1
    Friday, 24 February 2012, 17:05:27.


    Chassis Type: 8L - Audi A3/S3
    Scan: 01,02,03,08,15,16,17,22,35,37,45,55,56,57,75,76

    -------------------------------------------------------------------------------
    Address 01: Engine Labels: 06A-906-032-AUM.LBL
    Controller: 06A 906 032 HJ
    Component: 1.8L R4/5VT 0002
    Coding: 11500
    Shop #: WSC 79152
    VCID: 6DAD4AB7349F
    WAUZZZ8LX21001537 AUZ7Z0A1883166
    No fault code found.
    Readiness: 0100 1100

    -------------------------------------------------------------------------------
    Address 03: ABS Brakes Labels: Redir Fail!
    Controller: 1C0 907 379 E
    Component: ESP FRONT MK60 0104
    Coding: 0019970
    Shop #: WSC 01236
    VCID: 2C2B87B3CF05
    No fault code found.



    I'm going to go through the original fault code and see if I find any issues, so that's where I'm starting. Lets see where this goes.

    It's worth noting today it started slightly easier, but every time I got to rev the engine just a little bit it dies.... After 30 seconds - minute of idle dropping and rising it then pulls away fine. Odd?

  37. #36
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    iv got this on my a3 1.6 as of last night
    cured just by replaceing the pre cat lamba

  38. #37
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    Quote Originally Posted by Ads_AudiA3 View Post
    Ok, cleared the results and started again, this time I'm getting these results, apologies for not understand all the results but I don't think I'm missing anything blinding obvious here...

    VCDS-Lite Version: Release 1.1
    Friday, 24 February 2012, 17:05:27.


    Chassis Type: 8L - Audi A3/S3
    Scan: 01,02,03,08,15,16,17,22,35,37,45,55,56,57,75,76

    -------------------------------------------------------------------------------
    Address 01: Engine Labels: 06A-906-032-AUM.LBL
    Controller: 06A 906 032 HJ
    Component: 1.8L R4/5VT 0002
    Coding: 11500
    Shop #: WSC 79152
    VCID: 6DAD4AB7349F
    WAUZZZ8LX21001537 AUZ7Z0A1883166
    No fault code found.
    Readiness: 0100 1100

    -------------------------------------------------------------------------------
    Address 03: ABS Brakes Labels: Redir Fail!
    Controller: 1C0 907 379 E
    Component: ESP FRONT MK60 0104
    Coding: 0019970
    Shop #: WSC 01236
    VCID: 2C2B87B3CF05
    No fault code found.



    I'm going to go through the original fault code and see if I find any issues, so that's where I'm starting. Lets see where this goes.

    It's worth noting today it started slightly easier, but every time I got to rev the engine just a little bit it dies.... After 30 seconds - minute of idle dropping and rising it then pulls away fine. Odd?
    Based on the SAI fault code and the rough idle I would still say its the vacuum pipe coming from the N112 valve to the SAI... makes sense that this only occurs when cold as the SAI is only on suring the initial part of cold start so the vacuum leak is only happening when the valve is open trying to provide vacuum to the SAI..

    I would still be checking the vac pipes going to the SAI... the N112 valve is underneath the metal plate bolted to the inlet mani... there is a guide in the stickies for deleting the SAI (and N249 bypass) that will simplify the pipes under there...

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    It seems that some people have had similar problems, I'm going to have a route around when i can, hopefully this afternoon or one afternoon next week. What I do know is that this car is stage 1 tuned with a K&N on both primary and secondary air intakes (mini filter on the SAI). Might just do the tidy up and get rid of the extra pipework under the bonnet. After that it will be more investigating if it doesn't get better.

  40. #39
    sportquattro's Avatar
    4th Gear

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    Quote Originally Posted by Ads_AudiA3 View Post
    Can you let me know how it goes? I'm now working until Saturday afternoon so going to pick up a sensor Saturday afternoon and fit it on Sunday.
    Replaced the CTS this morning and car started instantly first go, temp rose to 90 deg fairly fast and much faster that it has of late so hopefully sorted cold start problem., Hope yours is an easy fix too.
    1999 Audi S3 Superchips remap, Forge 007p, Phatnoise, Black Diamond Discs & DS2500 pads, N249 Deleted, Badger 5 TIP, Poly dogbone bush, Bilstein B8's and Eibach Springs.

    1986 Audi Coupe Quattro 2.2 restoration project

  41. #40
    2nd Gear

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    Replaced CST and car started straight away. Will fault code later but hopefully all is fixed. Thanks for everyones help and input

 

 
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