A3 Cutting out after starting

Erikn89nl

Erikn89nl

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Hi guys, bit of a situation here...
My A3 (AGU) won't keep running. It fires up fine, then dies after half a second. No immobilizer light, and it'll rev to 3k with the pedal down, before dying...
VCDS won't talk to the ecu, not even main dealership could get in there... Has worked fine in the past.
Main dealership got it running again by removing, cleaning and refitting the throttle body. Just had a look, its clean as a whistle. Tried an improvised idle screw, to no avail...

Please help! I really need my car this week cause my partner's in hospital...
 
Unplug MAF next to Dump valve. It will probably be shot. AGU rely heavily on the MAF
 
Exact same thing happens with maf unplugged. Maf is just a few months old, too... Genuine OEM one
 
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Erikn89nl said:
Exact same thing happens with maf unplugged. Maf is just a few months old, too... Genuine OEM one
Click to expand...
Well I have an agu 1.8t, 2 things made it run like this.
Ignition amplifier on side of air box overheated.
The pipe under inlet manifold rotted away and it started to cut out.
Another common one is the fuel pump or filter.
If you have aftermarket radio it probably won't communicate with the ecu.
 
vacuum leak between inlet and up to brake servo?


Leak
 
I seem to have fixed it... Took the throttle body apart, checked all the solder connections, all fine. So I just applied some contact cleaner to the angle measurent tracks and sensor fingers, and refitted the thing... Car started and didn't die...

Hope it stays that way :D thanks to everyone who replied
 
Damn thing started doing the same thing, cutting out right after starting... cleaned TB again, didn't work. It also stopped auto-adapting with the ignition on (no noise at all from the TB). Got a used TB (same partnumber), it worked fine for a few days, now it's started pulling the same crap as before... Guess that rules out the TB.

Going to try the MAF and crank position sensor next...

Anyone got any advice?
 
New observation on the cutting out; seems to occur only when the car has been sat in cold air temps... it seems to fire up fine when it's been on a scorching hot carpark all day...

Does this ring any bells to anyone?
 
Thanks for finding that topic :)
I'll try replacing the CTS and relay next...
 
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audi upgrades
Sorry mate, haven't gotten round to ordering the parts yet.

Ofcourse in typical fashion, the car has stopped showing symptoms, except for bad fuel economy... The hot weather might've done it some good ;)
 
Wouldn't start at all this morning when I wanted to go pick up the CTS...
Spent hours taking stuff apart looking for the ecu relay... No idea where it is :S
Not under dash (driver side), not in engine bay (I have baro sensor where the fuse box is supposed to be...)

I did measure 12V on the nr.1 position on the ecu plug.
Battery died before I could try with the new CTS...
 
Ps. a few days ago (when it did run) it gave a code for MAF - low signal (tried to start with it unplugged, no difference)
And a code for "engine start blocked by immobilizer". Checked cluster for fault codes, none there...
 
audi upgrades
ECU is bone dry, no scorch marks or anything out of the ordinary...
 

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So you got a fault code for immobiser you say? It could be the cluster that's damaged or have you dropped the key? Do you have a spare key to try? I ask because I used to have a vauxhall astra gsi and I dropped the key and it stopped working the garage told me the immobiliser was the cause. About 300 later and I discovered when I put my spare key in the buggering thing started. Also the fuel relay under the steering wheel can stop the ecu telling the pump to prime.
 
Fuel relay is fine, pump primes when i turn the key.
Won't start with spare key either. Also, the immobilizer is in the cluster, which doesn't give any faultcodes.
 
It can also be the immobiser coil that goes around the ignition that has a bad wire. Check that too. From memory it has a wire connector
 
Erikn89nl said:
Fuel relay is fine, pump primes when i turn the key.
Won't start with spare key either. Also, the immobilizer is in the cluster, which doesn't give any faultcodes.
Click to expand...
How did you read the cluster? I thought the ecu wouldn't communicate mate
 
Cluster is separate module from Engine, Engine is the only module that won't talk.

I cleaned the contacts on the reader coil, no effect.
 
Nope, all intact. The ECU is "working" at least partially... Yesterday when i had the ignition on and plugged the ECU back in, it immediately started adapting the TB...
 
Without getting into too much detail as I don't want to cause a audi theft epidemic, you can buy something to bypass the immobiliser via the obd fairly cheaply. If you can't find it inbox me and I will give you a link. It's looking very likely that you have an immobiliser issue mate
 
Yeah, the 'not connecting' part worries me about that too. Also, unless you have an address in the Netherlands, I doubt they'd travel this far out ;-)
 
You may have to bite the bullet and get Audi to re program the keys.
 
The thought had crossed my mind... Sadly that one has the steering wheel fitted to the wrong side, and it's a ****** long drive from here
 
ha ha - yes you are right of course, sometimes you can transfer over the special bits and start again rather than spending hundreds and hours - I have put a Punto in to get a new clutch which I supplied - and if he charges more than £150 I will let him keep the car instead.

that particular example looks pretty good for £800 - what's that 900 euros? for a car with 12 months MOT, capable of upgrading to 200 BHP with hardly any effort.
 
Have tried one of the cheap code readers from eBay, about £12, the vag ones read engine,abs,srs and auto transmission, might be worth a try seeing as they are so cheap.
 
if the ECU is not reading you most likely need a replacement ECU

it's strange that the dealership was able to get things up and running again after touching the TB - have you properly scanned for codes?

if the engine module 001 is not reading - time for a replacement ECU (might say something like "missing message form ECU")
*any immobiliser fault will show up as an error
*any non communications fault with the ECU will show up with the no communications error in the instruments control module

wish you luck!!!
 
ayfreetee said:
Have tried one of the cheap code readers from eBay, about £12, the vag ones read engine,abs,srs and auto transmission, might be worth a try seeing as they are so cheap.
Click to expand...

I have a china-cable with VCDS Lite. No response from controller, only on Engine Control Module.
Roadside assistance has generic code reader. No response from ECU.
Main dealership had a go with their diagnostics setup. "Could not communicate with the Engine Control Module" according to them.

IanPG said:
if the ECU is not reading you most likely need a replacement ECU
Click to expand...

ECU seems to be working (TB is aligning). However, ECU and cluster aren't talking to eachother. This is the same route the K-line takes, so fault should be between cluster and ECU.

IanPG said:
it's strange that the dealership was able to get things up and running again after touching the TB - have you properly scanned for codes?
Click to expand...

Yes, got a code for MAF signal too low (tried to start without it connected, no change), vehicle speed sensor implausible (been there forever, never upset anything), and 'Engine start blocked by immobilizer' (likely culprit).

IanPG said:
if the engine module 001 is not reading - time for a replacement ECU (might say something like "missing message form ECU")
*any immobiliser fault will show up as an error
Click to expand...

Instruments control module reads every time using VCDS, no fault codes.

IanPG said:
*any non communications fault with the ECU will show up with the no communications error in the instruments control module
Click to expand...

This is the part that is confusing me. The cluster is convinced it has talked to the ECU. The ECU seems to believe there is a problem with the immobilizer, while the cluster assures me it's fine... Something seems to be going wrong between these two components, which would also explain the lack of communication with the ECU in VCDS while the non-starting is going on...

Anyone have access to a wiring diagram for an AGU?
 
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