2000 Audi A2 1.4 - Random loss of performance / misfire

Topsie

Topsie

Member
I'm getting an intermittent loss of performance that develops into a serious misfire.

Seems to go back to normal after letting the car sit.

From the codes I'm thinking perhaps an earth fault?

Will update with fault codes once the fault re-appears to see what's a red herring.

12 Faults Found:
17812 - EGR System: Basic Setting not Performed
P1404 - 35-00 - -
16688 - Cylinder 4 Misfire Detected
P0304 - 35-10 - - - Intermittent
16688 - Cylinder 4 Misfire Detected
P0304 - 35-10 - - - Intermittent
16825 - EVAP Emission Control Sys: Incorrect Flow
P0441 - 35-10 - - - Intermittent
17847 - Potentiometer for EGR (G212): Error in Basic Setting
P1439 - 35-00 - -
16524 - Oxygen (Lambda) Sensor B1 S2: No Activity
P0140 - 35-10 - - - Intermittent
17647 - Fuel Injector for Cylinder 3 (N32): Open Circuit
P1239 - 35-10 - - - Intermittent
17646 - Fuel Injector for Cylinder 2 (N31): Open Circuit
P1238 - 35-10 - - - Intermittent
17648 - Fuel Injector for Cylinder 4 (N33): Open Circuit
P1240 - 35-10 - - - Intermittent
17645 - Fuel Injector for Cylinder 1 (N30): Open Circuit
P1237 - 35-10 - - - Intermittent
16710 - Knock Sensor 1 (G61): Implausible Signal
P0326 - 35-10 - - - Intermittent
18043 - Powertrain Data Bus: Missing Message from A/C Controller
P1635 - 35-10 - - - Intermittent
 
My first guess would be to look at the coil - that ultimately was the main cause of our serious AUA misfire issues, due to loss of insulation around the back of the casing where the potting compound had dried out and was no longer sealing the casing and a small crack in one of the cable sockets so the sparks were escaping. By that stage I'd already replaced TB (very dirty), EGR (defective), injectors (sent away cleaned and checked), plugs (mismatched and old), cables (original) and a partridge in a pear tree, but each of these made things a wee bit better until the coil seemed to put the icing on the cake. Occasional air leak minor errors still crop up randomly but they mostly go away without any pattern to them.

Looking at that list, have you tried clearing them and seeing which ones remain / return and how quickly? The generality of the issues does suggest something common like an earth as you suggested although some of them could have arisen if the battery charge level has been less than perfect at some point. Starter motor earth cleaned? That also helped a bit with all three of my cars.

Best of luck, I'm sure someone with much more knowledge will be along soon.
 
I have cleared and just get the EGR fault return, however haven’t taken her for a drive yet.

I’ll keep the tablet in the car incase it throws another wobbly - I am leaning towards coil pack as it seems to be when it’s wet that it starts to misbehave.

Starter Earth is good, just recently had the starter out. Does the headlight Earth have anything to do with coil pack/ injectors?
 
Topsie said:
I have cleared and just get the EGR fault return, however haven’t taken her for a drive yet.

I’ll keep the tablet in the car incase it throws another wobbly - I am leaning towards coil pack as it seems to be when it’s wet that it starts to misbehave.

Starter Earth is good, just recently had the starter out. Does the headlight Earth have anything to do with coil pack/ injectors?
Click to expand...

Good to hear the earth is sound. Unsure about the earthing for the coil / injectors, however I would start by taking the coil pack off and have a good look at the back side and underside of the casing - in situ ours just looked a bit dusty, it was only when I took it off that I realised how deteriorated it was in places that you couldn't see. For the sake of 2 minutes with an Allen key it is an easy thing to check, and easy to replace with a new one. I ended up getting a Bosch - an overnight delivery Amazon one was instantly better than the knackered original but one output failed after 5 minutes (sent back for refund), so the Bosch that took 3 days to be delivered was ultimately what sorted it out.
 
Robin_Cox said:
Good to hear the earth is sound. Unsure about the earthing for the coil / injectors, however I would start by taking the coil pack off and have a good look at the back side and underside of the casing - in situ ours just looked a bit dusty, it was only when I took it off that I realised how deteriorated it was in places that you couldn't see. For the sake of 2 minutes with an Allen key it is an easy thing to check, and easy to replace with a new one. I ended up getting a Bosch - an overnight delivery Amazon one was instantly better than the knackered original but one output failed after 5 minutes (sent back for refund), so the Bosch that took 3 days to be delivered was ultimately what sorted it out.
Click to expand...

Injectors switch on earth, so the shared live is what would need looking, I’d check and clean the t17 coloured plugged near the ecu and check the ecu pins for corrosion


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Edwrai said:
Injectors switch on earth, so the shared live is what would need looking, I’d check and clean the t17 coloured plugged near the ecu and check the ecu pins for corrosion


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Click to expand...

T17c pin 15 which is the black one from checking.


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I’d also check the earth point in the passenger foot well as these are used by the ECU. The ecu and it’s components don’t use any engine bay earth points, earth point 44 power part of left A pillar is where I would check and clean first.


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Cheers all,

Will whip the coil pack off and take a peek and check the earth point in the footwell - if I still get no luck I'll check the ECU pins and plug (if the fault code comes back, I'm hoping the open circuits are a red herring).

Nick
 
Topsie said:
Cheers all,

Will whip the coil pack off and take a peek and check the earth point in the footwell - if I still get no luck I'll check the ECU pins and plug (if the fault code comes back, I'm hoping the open circuits are a red herring).

Nick
Click to expand...

It’s worth visually inspecting the black connector while you are there unplugging and looking for any corrosion


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So today I took the car for a drive and sure enough it started giving me some occasional hiccups. I picked up my Polo dipstick and guide and grabbed an NGK coil pack while I was out.

I read the codes when I got home to find only “misfire detected cylinder 4” and removed the coil pack to take a look. There was a tiny bit of corrosion on one of the leads on the coil pack end, but I replaced the pack anyway.

Happy to report back that the random misfires have now disappeared and a general all round improvement in drivability.

Thanks again for all the suggestions.

Nick
 
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