Stumbling on acceleration...EGR, lean fuel and fuel injector codes

H

henryf

Member
Hello all, looking for some advice here. Just picked up an Audi A2, within 5 minutes of driving away the engine started stumbling on acceleration, particularly half throttle scenarios and on came the engine light. I gave it a scan and got EGR excessive flow and Fuel trim system too lean fault codes. Anyway, I drove it again and the hesitation/stumbling has got far worse, the revs keep jumping up and down. I scanned it again, still have the two above codes and now I have two fuel injector short to plus fault codes. I have included a picture of the latest scan below.

I have noticed the EGR valve is sucking through it's vent pipe so I assume first thing to do is to change that and work from there. I can see how this could result in a fuel system too lean as well. However, does anyone have any thoughts on the short to plus fuel injectors? Unless the injectors are overworking to compensate for the extra air I can't see how the two could be linked? Any thoughts as to what other issues could be around here? As I say I'm trying to get the EGR swapped asap.



Any help would be much appreciated, cheers!
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Welcome! Just wish it was under better circumstances.

In spite of the thumbnail image it is possible to see the Marelli in the ECU title suggesting you have a petrol-engined (and probably 1.4i) A2?

Can you confirm this and give a bit more detail such as model year (reg plate year?) as this will direct us towards which engine it is likely to be - early petrol 1.4 AUA (single coil supplying all four cylinders), or BBY (four separate coil packs, one for each cylinder) - which in turn makes certain questions and guidance more likely.

On my AUA on purchase I needed a new throttle body and EGR, ultimately what turned out to be a new coil pack (caused stumbling / misfire on part throttle), and then basically everything else in the fuelling and ignition to make up for everything being 20 years old and poorly maintained in the recent past - new plugs (replacing four individually-different ones), four leads (originals were very poor, refurbished injectors (made a huge difference), and finally a new pre-cat lambda (NGK LZA11-V1 Oxygen Sensor) - which all together resulted in it going from running badly with poor fuel consumption to running very smoothly and 10-15% better fuel economy.
 
Also think about getting a new oil filler lid for the rocker cover as these are both cheap and can solve some air leak problems.
 
Hi Robin, thanks for the reply, apologies should have included the car details! It's a 2002 1.4 petrol engine, I believe AUA. Certainly looks to have a single coil pack serving all four cylinders

Edit: I have also improved the thumbnail image to full size (hopefully!)
 
Image much better! Ta.

In terms of things you can do without opening anything up - just as a quick one for the coil - it is simple to unscrew from the end of the engine. Remove it and have a really good look at the casing all over for cracks and the insulation / potting compound on the rear coming away from the exterior - sparks are lost through this to the engine block. Was the key issue leading to the misfires and rough running on light throttle in my case, although lots of other things needed doing to get it running properly.

The fault code relating to the injectors may well be a hint as well, although that's not one I encountered - my injectors were just really mucky and not giving a good spray pattern or delivering the same amount as each other either.
 
Ok, so I replaced the EGR valve last night with a working pierburg one. So far (after 1 hour of driving) the stumbling has totally gone away and the engine light has remained off. So fingers crossed.....

However, one small thing, I notice there are two different types of EGR valves - is there a difference between the two? I believe below are the model numbers of each type?

Type 1:
OE 036 131 503 M

Type 2:
OE 036 131 503 R
OE 036 131 503 T

Cheers for the advice so far!
 
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