Misfire 2002 facelift 996

Got a slight misfire on a 2002 facelift 996 C2, plugged in and have the code PO306 Misfire Cylinder 6. I'm thinking a coil or plug but I noticed a strong smell from exhaust, smells like the CAT, maybe a possible 02sensor? Anyone been down the same road?

As it is just one cylinder, it is most likely the coil pack or plug. If it was an O2 sensor it would affect the whole bank.

Thanks for the reply Richard! The car doesnt run too badly, just really at idle I get a little misfire; oil pressure and temp is good, the CEL light doesnt stay lit permanently but does go off and on and different intervils. I'll replace the coil and plug and see how it goes first. Would it be worth doing a complete coil and plug change at this stage?

Depends on your mileage, whether the plugs are due for change, and the state of the other coil packs. If they look a bit tatty - splits and cracks in the insulation - I would change them.

With Richard all the way. You also mentioned Cat smell, this is the unburnt fuel caused by the missfire, the fuel passes through the monolith causing the catalyst to go into overtime which develops the eggy smell as a result. Always attend to missfires immediately as further damage will occur. :thumb: Lloyd

+1. They're a bitch to change, just done mine. Lloyd will supply at the best prices if you ask him nicely! Ray :thumb:

Thanks for all the replies! Going to take a look at this tomorrow hopefully. From what I read, cylinder 6 is on the drivers side and furthers in, if your standing at the rear. Would that be right?

Yep, the coil nearest the drivers seat. Possibly the easiest one to change, if you are doing them all ask Ray, I do believe he is up on technique! cheers for the heads up Ray

Lloyd can you PM me a price for all 6 coils please as I'm thinking of doing a complete plug and coil replacement while I'm at it.

Thanks for the vote of confidence Lloyd. Here's my top tips for changing these bas*ards. 1. Jack up car and support with axle stands - we don't want any accidents if your jack fails or topples. Good lighting is essential. 2. Have a selection of small 'open ended' and 'ring' spanners as well as hex or T bits depending on yor fixings available to remove the bolts. I think the heat shields are 10 mm and the coils are T30, but these might be hex in your case. You might want to change some or all of the coil bolts as the heads get corroded. 2. Be careful when removing the electrical connector off the coil. Push back the rubber boot and then get a small screwdriver and genttly lift the tab, the connector should spring off. 3. When removing the coil bolts you may need to improvise by holding your Hex or Tox bit with a small ring spanner. I wedged my bit into the ring with a small piece of polythene - this stops the bit falling out when you're trying to locate in the bolt head. Always replace the bolts with copper grease to stop them seizing up. 4. Install the coils with liberal amounts of silicon grease, both HT and LT connector sides. 5. If the Low tension LT connector has snapped off you'll need to improvise to keep it in position. I used a tie wrap anchored between the connector loom and the lower coil bolt. To do this I had to make a figure of eight shaped washer, one end for the tie wrap and the other for the coil bolt. I found a bracket from a kitchen cabinet that had 3 holes in it. Got my angle grinder out and hey presto job done....... A new wiring loom is £900 + vat Good luck Ray :thumb:

I had a similar problem to the OP. Misfire at idle on one cylinder, fine when above 3k RPM, Engine light flicking on and off. It's currently got the engine in bits as the valves have corroded (despite being less than a month old). The repairing garage suspects faulty parts or possibly even dodgy fuel has caused the damage.