Hey all, I just recently bought a 2002 SE 6 speed with 147k on it. I've only had the car a few weeks, but on a couple of occaisons, when it's cold, I will get a flashing CEL... Car will go into limp mode and run badly. I can clear it up by turning it off and back on. Idle seems low and rough at like ~500 rpms... I scanned the codes and got: P0304(cyl 4 misfire, is this up front?), p0300(cyl misfire), and p0138(o2 sensor, bank 1, sensor 2). I don't want to take it to the dealer for obvious reasons... But could this be as simple as a bad coil pack? My brother in law suggested clearing the codes with the scantool and switching the coil pack to another cyl and re-scan later, does this seem like an appropriate next step? Or is the o2 sensor causing the issue...

Really don't like having issues this early on into my relationship with this car, haha.

 

Yes, switching the coil may help diagnose your situation. Just swap it with another cylinder and then if the misfiring cylinder changes then you have your culprit (or one of them at least).

Flashing CEL is an emissions thing, it simply means that your car is misfiring but you would probably notice by the way the engine is running anyways.

 

cylinder 4 is at the front of the car, middle cylinder so easy access. Most likely is a bad ignition coil but you can test it by switching it to be sure. Flashing CEL typically means it's very bad misfire and will damage your engine if you drive with the CEL flashing.

I'd say start with changing the cylinder 4 coil and going from there. Test it if you want first.

 

Thanks for the replies. By test, do you mean using a multi meter on it? Yeah, I turned the car off right away when the CEL came on flashing... ran really badly. I'll swap #2 and #4 and see what happens.

 

You can switch it and check or you can simply unplug it and see if the engine still operates the same(IE its a bad coil) or it idles worse(IE its a good coil). Switching it is just more work. Unplugging the clip is easier. A good coil does its job so if you unplug it, engine idle gets worse whereas if its already bad nothing changes. BTW, if it is bad, get the OEM replacement. Many people have issues with the aftermarket coils from the auto parts stores

 

How does a good coil still operate when you unplug it? The car doesn't have a steady CEL or anything, and right now it idles fairly smooth... it's not like an idling big block or anything... it's just a smooth engine that any idle issue is noticeable... I just got the oil changed and it seemed to run better since it's warmer outside than normal... Would that point more toward the o2 sensor?

 

Just change the coil and change the o2 sensor. That is all.

 

No, unplugging the coil makes it not work. If the coil is good then the engine will idle worse telling you the coil is good becuase when you plug it back in, it obviously goes back to normal. If the coil was bad, when you unplugged it nothing would happen because it is doing nothing. It wouldnt matter if you left it unplugged lol because it is not working anymore. See what I mean? Its the easiest, and most accurate way to test coils because they can test fine with a multi-meter and still be bad.

 

Well I swapped the coils because they are up front and that takes 2 seconds. I went to clear the codes and decided to scan it again, just to see if anything changed in the couple days it's been since I scanned it... the two misfire codes were gone, leaving only the o2 sensor... so I cleared that. And will check again in a couple days. Hopefully it's just that.

 

When all is said and done the answer will still be replace the coil and o2 sensor. Lol just do it!

 

You're probably right... car went into limp mode again misfiring bad this morning. I called my local dealer to see how much the parts are, the coil is $107, and the sensor is $195... After looking for new struts and tires, and now this... I'm really surprised at how pricey the parts are for this car... and this from a guy who's had a few turbo VW's...