99 MK4 Golf 2.0 AEG – Severe performance issues

I have a 1999.5 Golf GL with the 2.0l 8v AEG engine. Let me just give you some background info on this car.

A couple of months ago the engine started miss firing and running rich. We looked for vacuum leaks, but didn’t find any. As a precaution we changed the plugs and wires as they were coming up.. In the end it was a collapsed catalytic converter that was clogging the exhaust. A mechanic friend cut open the exhaust and banged out the bits and pieces. There was pretty much no catalytic material left. So my car really doesn’t have a working emission system, and would trip the O2 sensor and bring up the P code about converter efficiency . I had tracked down a used one, until a few days ago the car began running really bad and there were 5 codes waiting for me.

What my current plugs look like:

P0606 – ECM fault code
P0420 – Catalytic Efficiency
OS1 – Heater Malfunction on Oxygen Sensor
Missfire Cylinder 4
P1582 – Idle Adaptation Limit Received

The ECU code is one that pops up every couple of months and I haven’t been able to figure it out. It usually goes away after I turn the car on and off.

As for the Oxygen sensor I linked that to the missfire. The things is I have a Haynes manual with the electrical stats for that sensor and it doesn’t match yup. I probed the sensor unplugged and the heater showed an open loop on my meter…maybe the heater was finished. I backprobed the sensor plugged in and with the ignition in the “ON” position for power. The sensor wires according to Vw are supposed to have 400 -450 milivolts…it had 440, but the heater wires were supposed to have 12V and they only were providing 0.125V well below the specs. With the car on and warmed up the sensor voltage was supposed to fluctuate between 100 – 900 millivolts , it stayed at 420-440 mV. The sensor and the heater voltage is controlled through the ECU, but I’m trying to find out if there is a fuse between them. The P1582 code has popped up twice since owning the car, I got a friend with a RossTech system to reset it.

As of right now i’m not sure if my sensor is bad or something much bigger is going on…