Good Day- I have a 1999 A6 quattro 2.8 w/ 178,000 miles. Over last 2 weeks I have been getting all six fuel inj codes (P1236-1242 Fuel Inj. Circ. Open Circ) at the same time. I have searched for clues (forums,etc)to what would be causing all six codes to trigger- Below is what I have replaced recently:
- New Wires & Plugs, Air Filter, Cleaned Air Mass Sensor, Replaced Fuel Filter, Clean Throttle Body, Ran Seafoam in Gas Tank for 2 weeks (to clean injectors), New Alt & Battery, New Crank Case Breather Hose: (all w/in 8-10,000 miles)

Current Symptoms: Every other day the car cranks but takes a few seconds to start-when it does it is a slow build and I assist by pressing the accelerator to get it back to life (this is when Codes appear). While driving it seems fine except for erratic shift points or inconsistent idling (not hard or jerking). Fuel Economy seems fine 20 mpg hwy/city combo- (I live in the Northeast-starting to get cooler)

Also, I have disconnected battery to reset ECU, checked electrical connections and vacuum hoses:

I have heard the following may be the culprit- please verify my finding:
1) Clogged pressure control valve, check valve and suction pump
2) Replace Fuel Pump (i am getting fuel to the rail)
3) Ignition Coil? (would this effect the Injectors and Shift Points?
4) Replace ECU?

Your help is much appreciated and let me know if I need to double check my work above!

 

I would concentrate on items #1 and #2. The SeaFoam might have clogged either the pump or the filter.

Bob

 

Okay- but the Fuel Filter was replaced two days ago after the use of Seafoam in gas- Thanks for the reply- I will let you know if any of those worked

 

not sure if it matters but this seems tobe happening when the outside temp is cooler 35 degrees

 

its probably something electrical, as much of a PITA those are.

 

All connections from ECU to injectors were checked and cleaned- no sign of moisture in ecu box- I am thinking the ecu is beginning to fail? Is there a way to test if ecu is failing as this is intermittent or any other electrical connection I should be thinking about? note: I have NOT had any misfires- this happens only start up. Thanks again for your help!

 

FYI- It was the vacuum hose to the fuel regulator. It was spongy causing it to collapse, especially at start up- this lead to the starting issue and codes. Also, caused erratic shifts. I also reset the ecu (unplugged battery overnight)- it has been close to a week and no issues- Note: I replaced all the vacuum hoses (apprx 5ft worth of hose @ $8). It was easy and took just a few minutes over an hour to complete.

 

good find. Thanks for sharing the cause.