P0300, P0302 & P0304

[kavey95]

Some guidance please ..... '00 Boxster S, 16k miles. Stock.

After changing oil and spark plug tube seals, car ran fine for about 1/2 mile. Then misfire and CEL came on.

- Shut the engine within 1/2 mile and read codes: P0300, P0302 and P0304. Using Acton 9125 reader.

- Cleared codes and started car. Ran for about 30 seconds, same misfire. CEL did not come back on.

- Rechecked codes and one appeared, P0131

- Unplugged MAF connector, started car. No difference, same misfire.

- Cleaned MAF using CRC Elect cleaner. Looked pretty clean to begin with. Restarted and same misfire. No codes within 30 seconds. Stock air cleaner is clean.

Had enough and called it an evening. After a good night's sleep, I'm thinking possibilities are a bad coil, MAF or O2 sensor. I believe P0302 and 0304 are in both cylinder banks?

Since the car ran fine for 1/2 mile after the initial start, I'm thinking it may not be a non-properly connected coil/s or O2 sensor, but I'll check that first. If it's not those, would replacing coil be the next step? Would like to avoid throwing money with guessing at parts, but wanted to do all I can within reason before taking it to the dealer or indie.

Pretty bummed and sore right now - guidance would be very appreciated! ....

Edited July 6, 2009 by kavey95

[Loren]

P0302 Misfiring, Cylinder 2

P0304 Misfiring, Cylinder 4

P0300 (Multiple) Misfires Detection (Sum Total)

Then MAF would have nothing to do with two cylinders misfiring. O2 sensors are telling you about the problem they are not causing the problem.

Check the spark plug connectors and the coil packs on cylinders 2 and 4 - chances are the connector is not on all the way or the coil packs are over torqued and cracked.

[ericinboca]

Some guidance please ..... '00 Boxster S, 16k miles. Stock.

After changing oil and spark plug tube seals, car ran fine for about 1/2 mile. Then misfire and CEL came on.

- Shut the engine within 1/2 mile and read codes: P0300, P0302 and P0304. Using Acton 9125 reader.

- Cleared codes and started car. Ran for about 30 seconds, same misfire. CEL did not come back on.

- Rechecked codes and one appeared, P0131

- Cleaned MAF using CRC Elect cleaner. Looked pretty clean to begin with. Restarted and same misfire. No codes within 30 seconds. Stock air cleaner is clean.

Had enough and called it an evening. After a good night's sleep, I'm thinking possibilities are a bad coil, MAF or O2 sensor. I believe P0302 and 0304 are in both cylinder banks?

Since the car ran fine for 1/2 mile after the initial start, I'm thinking it may not be a non-properly connected coil/s or O2 sensor, but I'll check that first. If it's not those, would replacing coil be the next step? Would like to avoid throwing money with guessing at parts, but wanted to do all I can within reason before taking it to the dealer or indie.

Pretty bummed and sore right now - guidance would be very appreciated! ....

I don't know if an acton reader is going to give you accurate codes - it might, i just don't know.

300 - 306 are misfire codes - 300 being the sum total and 301 being culinder 1, 302, cylinder 2, etc.

131 is low voltage to 02 sensor. Did you disconnect the connector on the 02 sensor to get to the coilpack? If so, be sure it is tightly and prperly reconnected.

If it were me, I would use a durametric to clear all the codes, drive it to see if anything comes back, and then read the codes. We'll see if the other guys have any better ideas.

[krums]

I had a very similar problem. I took it to a specialist and they done cylinder compression testing, tried changing all the plugs, coil packs, etc. In the end I took it to another Porsche specialist and all they done was opened and cleaned and cleaned all the air pipes coming and going to the throttle body and made sure they were properly tightened and the car worked perfectly fine afterwards.

The guy had dealt with the same problem before, he said sometime the car takes in air after the throttle body due to a loose pipe connection which causes the engine not to work correctly as too much air is going in.

[kavey95]

Thanks everyone for your analysis -

Based on the order of the codes received, it makes sense that the misfire is likely the coil pack/s. The 02 sensor is downstream indicator of the misfire, and MAF is likely unrelated.

Whew, feeling like I can fix this !

[kavey95]

Going through the troubleshooting, number 2 and 4 coil connectors weren't 'clicked' in all the way. After checking the others, car started and ran beautifully - rechecked the codes and all clear! I'll figure a way to locate a durametric and clear the further embedded codes.

Thank you all again for your advice, and so quickly - this board is awesome!

Edited July 12, 2009 by kavey95