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Discussion Starter #1
Hi all, we have a 2004 vw golf w/ 150K and are troubleshooting p0302 and p420 codes. I figure I'd start with plugs, wires, fuel filter, and a basic tune up. Need to get smog done! Thanks for any tips and guidance.

:hump:
 

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16686/P0302/000770 - Cylinder 2 Misfire Detected

Possible Causes
Ignition system
Fuel injectors
Fuel pressure
Running out of fuel
EVAP canister purge valve
Evaporative emission system
Low compression
Base engine problems
Controle Module damaged
Special Notes

This feature search for engine misfire in a specific cylinder. Most of the time the cause for a misfire is a lack of combustion in a cylinder due to absence of spark, poor fuel metering, or poor compression.



16804/P0420/001056 - Catalyst System; Bank 1: Efficiency Below Threshold
Possible Causes
Leakage in Intake and/or Exhaust System
Catalyst faulty
Oxygen Sensor(s) faulty
Oxygen Sensor(s) Control faulty

Possible Solutions
Check Intake and Exhaust System for Leaks
Check Catalyst
Check Oxygen Sensor(s)
Check Oxygen Sensor(s) Control
Perform Oxygen Sensor(s) Aging Check

Special Notes
For 1.8T's experiencing this fault code, this thread may be useful: VWVortex.com - Aftermarket DP/Cat -DTC - Cat efficiency below threshold - Who has this DTC and wich DP/Cat
 

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Had same codes come up similar mileage, Check coil pack for any small cracks for P0302, replaced mine and fixed that code havent seen it in 10k kilometers, as for P0420, trying out an 02 spacer once weather gets better
 

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Discussion Starter #5
ok im trying to replace the fuel filter. the parts guys keep giving me this big filter with 1 in 1 out. What I believe to be the filter on my gold has 2 ins and 1 out. In other words 3 pipes on it.
 

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Discussion Starter #7 (Edited)
I replaced the plugs, couldn't get to the wires initially. Ran well. Got smog done and it passed no problem. Car was running great....

Then this weekend it started running like crap. Sounds like its missing, almost stalling out.

Listened under hood and was hearing a snapping sound from one of the middle cylinders. Re tightened down plugs to about 15#. Replaced wires with new wires. Reseated fuel injector plugs I could reach and its still running like crap.

Not sure what to do next. ��
 

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Discussion Starter #9
Ok -ordered a beck arnley coil pack today. Tonight, decided to use from old fashioned troubleshooting and ran the engine at night to see if I could see a spark. I see a spark coming from the could pack and am pretty sure the snapping noise is from there. We'll see...
 

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Discussion Starter #10
ok - installed coil. still running like crap. checked codes and found injector / ignition codes on cyl 3. Pulled plug and did a continuity check. IT WAS BAD!!! After all this and the damn plug was bad. Installed an old plug and it ran like a champ. WTH happened? Plug just crapped out?
 
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