Audi A2 1.4 AUA - Hard & Spluttering Starting

[Professor Falken]

Good evening Ladies and Gents,

Many threads on Audi A2s, hard starting/ long cranking etc but I really do need some help and wisdom on this one.

Car is a 2001 1.4 Petrol AUA, 114,000 miles and drives nicely.

The car sometimes starts perfectly, sometimes its a long crank then splutters into life but there is no real pattern to this happening. It can be cold or warm, left overnight and sometimes it just long cranks and splutters then starts or starts perfectly. If I turn the key to position 2, count a couple of seconds then start it seems to be a lot better and will always start this way.

So to cover off a few questions and things I have already done in my rather large quest to resolve this:

1) The car when started drives perfectly, without fault and MPG is good
2) There are no lights on the dash and no error codes in VAGCOM
3) According to VAGCOM everything is good and working, sensors giving good readings and measuring blocks look good
4) Earth points checked and cleaned, under the bonnet by the lights and the two A pillars
5) Car has been fully serviced including new spark plugs, oil and filter
6) New Bosch HT Leads fitted
7) New NGK Ignition Coil fitted
8) New Fuel pump fitted
9) New Fuel filter fitted
10) New coolant temp sensor fitted
11) New MAP sensor fitted
12) New camshaft position sensor fitted *updated
13) TPS checked and adapted
14) Throttle body checked, cleaned and adapted
15) New Injectors fitted
16) One way valve fitted to fuel pipe leading into the fuel rail to see if there was some form of pressure drop at the rail itself
17) No fuel leaks that I can see from the tank, pipes or engine bay
18) Fuel pipes look all good, no fuel smells, leaks or drips
19) Injector cleaner and fuel cleaner run through the system
20) New Varta Silver battery installed
21) New PCV Oil Separator fitted
22) Pipes and breathing looks good on the car, no obvious vacuum leaks
23) New Oil pressure sensor fitted
24) Spare Key tried in case this was immobiliser problems
25) New Fuel Relay (612) fitted
26) New front Lamda sensor fitted

With all of the above done, whilst making the car run even better made no difference to the starting problem.

Anything I am missing here?

Help and wisdom would be very much appreciated as I am running out of ideas.

 

[audifan]

What condition are the battery terminals in? What condition is the auxiliary positive supply box, connection to the positive clamp and internal connections? What is the negative connection like as it contacts the chassis near the left rear wheel? Although you have cleaned the headlight earth what about the cable? Is the cable internally corroded? Does the problem go away if you temporarily use a jump lead between the chassis earth and engine block? How good is the ignition barrel? Do you have any burnt high power relays?

Pretty much none of the above would show a fault either in VCDS / Vagcom nor set a warning light. So my guess is it is electrical or lack of.

One last thing is what condition is the exhaust in, could you have a partial blockage or internal part come loose especially in the cat?

 

[Proghound]

I can't see the camshaft position sensor having been changed. It may be only just communicating with the ECU on enough of a basis to stop an error being thrown. Possibly the 2-second wait is allowing it to 'wake up'? To diagnose it, disconnect it. The ECU will take a couple of turns longer to work out what position the engine is in from the crank sensor and fire the correct cylinder, but reliably so.

 

[Professor Falken]

Thank you for the replies.

Cables on the battery all good, cleaned and not corroded. Condition of the earth leads were also good but not tried to bypass or check so will do that. Exhaust in good order also, but will have a look and get the meter on the earth leads over the weekend also to confirm that's not dragging anything down. Plus check where the negative is on the chassis and see if that's in good order.

I will also order a new Crank position sensor, I have checked and its the Camshaft sensor I have in fact changed so will do the other as that's the last sensor on the list so may as well do them all.

Now I am trying to work out the version needed. Part number for the crank sensor is 030 957 147 but for the AUA it lists B, N or AB suffixes for versions from older to newer.

 

[Professor Falken]

Good afternoon all,

Been spending more and more time on this one as the problem remains and is possibly now getting worse, all the sensors have been changed (Including Crank & Cam etc as discussed above).

It looks like the ECU could well be the problem.

Interesting the car is a 2001 but has a 2005 dated ECU in there when I checked over this weekend, which was a little odd and I suspect someone has been in there before me.

ECU connections looks Ok and cleaned them etc just in case but that made no difference, no visible damp or damage inside the unit but it has been opened before and resealed by another person before me.

ECU Model is Marelli 4MV 4030 (VAG 036 906 304 EG) which looking at VCDS is I think fitted gen immobalizer 3 (16 digit VIN and 14 digit Immobiliser code strings shown under VCDS).

Now at some point the ECU has probably been changed and either someone has coded out the immobiliser or it's starting to go wrong. On some days on the dash I get the Immobiliser icon come up, it cranks for 5 to 10 seconds and will always start (Once started everything is OK, does not stall or cut out). It feels like the fuel pump is not being switched on by the ECU initially and it takes time for that to happen hence the long cranking. Added to that I can start the car with the spare key without the immobiliser chip in it but with the same long crank scenario does also occur.

So something has been played with, messed with or just now after 22 years its going wrong. Therefore is the best route to get a second hand ECU from eBay and swap using VCDS with the PINs from both or send the current ECU off for repair?

Would good to hear from the forum who has had failing ECUs what they ended up doing.

I wanted to attack this one as I doubt its going to get any better soon!

 

[kp 115]

I

Good afternoon all,

Been spending more and more time on this one as the problem remains and is possibly now getting worse, all the sensors have been changed (Including Crank & Cam etc as discussed above).

It looks like the ECU could well be the problem.

Interesting the car is a 2001 but has a 2005 dated ECU in there when I checked over this weekend, which was a little odd and I suspect someone has been in there before me.

ECU connections looks Ok and cleaned them etc just in case but that made no difference, no visible damp or damage inside the unit but it has been opened before and resealed by another person before me.

ECU Model is Marelli 4MV 4030 (VAG 036 906 304 EG) which looking at VCDS is I think fitted gen immobalizer 3 (16 digit VIN and 14 digit Immobiliser code strings shown under VCDS).

Now at some point the ECU has probably been changed and either someone has coded out the immobiliser or it's starting to go wrong. On some days on the dash I get the Immobiliser icon come up, it cranks for 5 to 10 seconds and will always start (Once started everything is OK, does not stall or cut out). It feels like the fuel pump is not being switched on by the ECU initially and it takes time for that to happen hence the long cranking. Added to that I can start the car with the spare key without the immobiliser chip in it but with the same long crank scenario does also occur.

So something has been played with, messed with or just now after 22 years its going wrong. Therefore is the best route to get a second hand ECU from eBay and swap using VCDS with the PINs from both or send the current ECU off for repair?

Would good to hear from the forum who has had failing ECUs what they ended up doing.

I wanted to attack this one as I doubt its going to get any better soon!

recall there being a software update available for the 1.4 aua engine someone maybe can confirm if relevant, check the fuel cap is the correct one as I believe it can effect starting/running.
Not definite as mines a diesel
Keith

 

[PlasticMac]

I

recall there being a software update available for the 1.4 aua engine someone maybe can confirm if relevant, check the fuel cap is the correct one as I believe it can effect starting/running.
Not definite as mines a diesel
Keith

The fuel cap is a potential cause of trouble on all the petrols, 1.4 & 1 6. It's because an air leak there will upset the fuel tank vent system.
Wouldn't be surprised if diesels could be similarly afflicted, as tanks can't vent to atmosphere, as that would result in emissions.
Mac.

 

[Professor Falken]

Thank you gents and to confirm new Febi fuel cap was fitted also as part of all the above fun.