Darel Matthews

I see this has been discussed pretty much to death, but without one conclusive answer, and in some cases with guys throwing thousands at the problem, which I need to avoid.

background: Car has always run flawlessly. Carbon cleaned w/ new plugs in Aug 2017, maybe 25-30,000 miles since.

Car sat pretty much all weekend. Monday morning, 30 degrees outside go to start it and it stumbles on startup for the first time. Runs fine on way in to work, no issues. Just never even heard it stumble on startup like that. No idiot lights.

Leave work, very slight stumble on start, smooths out within a second. As I pull away EPC comes on. No driving issues, runs like normal.

Today, morning start OK. No lights on. Leaving work start OK. Get about halfway home, on neighborhood streets (stop & go, slow speeds), EPC comes on.

All WARM starts are totally normal. Any stumbling is after car has sat for a while and does NOT carry over into driving - I have never noticed an issue driving, even when the EOC was on.

Get home, break out VCDS. 2 instances of P0087-02 fuel pressure low. Did some driving around with the data logger on, rail pressure demanded is almost identical to actual rail pressure all the time. 25-105 bar. I can't figure out where to see the low pressure tank output pressure on here? Of course, no EPC light while I was driving around, and I did vary from slow speeds to about 6K rpm, bogged the engine with some 3rd hear starts, etc. No issues.

Also on the VCDS, under "Mode 7 Pending DTCs" I was showing no current DTCs but for pending, I had P2293 Fuel Pressure Regulator Valve (N276) Mechanical Malfunction as well as the P0087 Fuel Rail/System Pressure: Too Low.

Does that P2293 narrow down my issue to a fuel pressure regulator valve?

I can probably easily throw 3 new fuel pumps on here and be done with it, but right now I don't have $200 for one HPFP let alone $700 for all 3 pumps. How do I begin troubleshooting this issue?

Thanks,
Darel

JRB_brownA5

HI Darel,
I'll throw out quick story of what my car did that was similar in the way it ran but had completely different codes.

One day my car started and ran fine but as I was driving it it started to shutter and miss-fire.
Shutting off and restarting sometimes fixed the problem. I went a day without issues but then it came back.

I put on the VAGCOM and got an indication of short to plus in ignition coil 4 P2310 and some other codes that I can't recall right now. I swapped around coils and the problem stayed at 4.
So i figured I needed to figure out where the short in the harness was.

When I went to pull the harness I discovered water and corrosion in the engine control computer connector.

The problem I had turned out to be a leak at a coolant valve and the water from the coolant valve connector works its way up the wire (inside the insulation) and eventually after I don't know how long it eventually started shorting out other sensors and devices randomly.

I filled out a NHSTA complaint because it turns out that Audi has already had a recall for this on the 2010-2013 A8 for the same issue.

I really didn't figure that I would have the same coolant valve since is is associated with transmission cooling and my car is a manual - but sure as poop, the Audi technician at my local dealer showed me where the valve is and pulled the connector and it was crapola.
I was able to clean up the ECM connector well enough to make things work but now I figure that the harness has at least 1 wire bad and the computer might be compromised also.

If you've go random things that seem electrical related with the ECM and aren't as lucky that the faults indicate a short, maybe take a look at the ECM connections.

John

Darel Matthews

Thanks John!
After I posted this, I ran some Techron fuel injector cleaner through for a couple of tanks, thinking that the fuel pressure relief valve might have been hanging up. I was thinking it seemed like the rail was losing fuel pressure when it would sit for a long period of time, like 48 hours or more. The problem hasn't returned since. In fact yesterday was the first time I drove it since Saturday (4 days) and all was well. Fingers are crossed. If it returns I will definitely look into that.

Darel