OH NO! CEL codes P300, P301, P303

Was driving along, stopped at a traffic light and all of a sudden it started idling a little rough and the CEL started to flash and the computer said to drive slowly to service Started to drive and after about 100 feet, the light went out and the engine was smooth again. I was about 1 mile to my home, drove home and plugged in my durametric There were 3 codes This is the first time I have gotten ANY codes I did a weekend at the track a week ago and all was good I have 74k on the clock,. Plugs were changed at around 15k miles ago Just did an oil change before I went to the track. All the oil changes I have done since i bought the car a year ago have been good Any thoughts????

Maybe the fuel pump is starting to act up - if it was bad gas or a clogged filter, I wouldn't expect it to stumble for a bit and then recover. Since it happened only at idle, a vacuum leak might be a possible suspect. Sounds like you haven't driven it any more since you got home and read the codes?

Incidentally, it's "OH NO! THE DREADED CEL codes P300, P301, P303"

Coils? Not sure why 2 would act up at once, but maybe they were already bad (cracked at the track) and something (hard bump) caused them to start showing symptoms simultaneously.

I drove it about an hour later for about 20 min and no codes and runs perfectly as before some stop and go neighborhood driving, a good high speed run on the freeway and then some neighborhood driving. maybe it was Sun Spots?

Bad gas. Or mice.

Might be moisture and cracked coils.

I think you need the dreaded new stable of coil packs. Need to get off my *** and do ours too (getting the 300 and 301).

Yea, could be the coil packs, but why would the CEL go out on its own after about 60 seconds?

If it is crack/water based it could be a transient short causing the misfire. Kinda surprised the CEL went out though. I thought once it was triggered it stayed on (flashing accepted) until it was shutdown and restarted.

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Because the error condition went away. Flashing CEL denotes rich misfires and this suggests a malfunctioning injector. If this is what is going on it is probably confined to one injector. The misfires in the other cylinder could have been self-inflicted as the DME dialed back on the fuel and leaned out the other good cylinders to the point one of them then developed lean misfires. When the bad injector recovered the DME of course resumed its normal fueling. At 74K miles coils could be suspect but I think the engine would manifest misfires upon cold start in cooler more humid conditions. I have to point out while the coils of the engines of both of my cars cause misfires occasionally after an onset of damp cooler weather none of far have misfired at any time other than just seconds after a cold engine start.

If the problem is cracked coils and them getting wet, I suppose I could spray some water up that side of the engine when it is running and see if it throws a code Is that a good idea? As far as the injector, I did put a bottle of Techron about a month ago before I went to the track. I would think that would clean the injector, not plug it. Should I put another bottle in the tank? The car also ran beautifully at the track and the drive to and from the track which was some great back road twisties up and down the mountain. Should I check the fuel trims or ???

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Spraying the water onto the engine/coils when the engine is running and warm is not likely to manifest any misfires unless the coils are pretty bad. If they were this bad they'd be misfiring without the need to wet them. Even though my Turbo misfires upon cold start once in a while when dampness comes in the only odd behavior the engine manifests when I start it after a washing is the belt slips from the water. The engine doesn't misfire. Techron can loosen deposits in the fuel system and it could have been a flake, a tiny particle that got caught in the injector momentarily before being pulverized and flushed out. Generally injectors are protected from this by fine screen so the particle would have to have been loosened from downstream of the screen, somewhere in the relatively small volume of the injector body that is between the screen and the tip/nozzle. It doesn't have to be a particle though. The injector is an electro-mechanical device and it could have suffered a momentary problem that caused it to not close completely or to for some reason react less quickly to the removal of power and thus extend the active time the time injector was open. If the latter it will likely do this again as the failure mode becomes less intermittent and more constant. There is another failure mode and that is an injector failed to open fully, and the DME added fuel to compensate and this triggered rich misfires from one of the two healthy cylinders. The sick injector recovered and of course the DME resumed normal fueling and misfires ceased. Regardless, I don't think -- at least this would be my opinion were the situation reversed -- I don't think the above is sufficient to warrant replacement of the injectors, even just those on the "bad" bank. For a more definitive diagnosis, maybe, would be to with a Porsche diagnostics computer connected to an up to temperature engine to disable each injector in turn and note teh RPM drop. The disabled injector that results in less RPM drop could be (could be) the "bad* one as that cylinder is contributing less than the other cylinders.

Can I do that with a durametric?

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That would be a good test. Generally I recommend peeps replace their coils while replacing plugs as most of these cars are 10+ years old and plastics will deteriorate from heat/age. You only need a micro-crack for codes to be thrown. When mine went bad, I couldn't even hardly see some of the cracks without breaking out the magnifying glass. Don't cheap out and replace all 6.

Also, even though your CEL isn't lite doesn't mean the misfires went away. It could be a pending code. Does the Durametric show pending codes? There is a lot of mind share on the P30X codes on rennlist. Just search and you will find a ton. Mine was fixed after replacing the cam solenoid seals. But yours could be as easy as coils.

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a durametric as well as a generic OBDII reader will show pending codes

Jay, with Duramatric you can check the following vitals: - cam deviations. They should be rock solid throghout the entire rev range - FRA, RKAT, etc http://www.callasrennsport.com/porsc...m-information/ - cylinder misfire counters in real-time when you are driving. Watch the road though if you don't have a passenger to help you. You may have misfires but not exceeding the pending code/CEL thresholds

I vote for coils. They are 11-12 years old. Plastic gets brittle over time and it breaks; end of story ... hopefully.

Try putting the water hose in the intake while in an underground parking garage.

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Try putting a water hose in your intake better yet, your exhaust Bruh, bro, brah, dude

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I gave them a really good soaking with the garden hose and all is still good I'm thinking Macster may have hit on it with a piece of dirt or something that got stuck in the injector and then spit out. I have a AX this coming Sunday, so it should get a good workout before taking it back to the track at the end of next week

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didn't check the trims, but CAM deviations were steady at 1.6 and 2.1 and the misfire counters were all zero

So just to sum up, you ask for our opinion, multiple people tell you its most likely the coils/plugs which is a well known and semi common issue (across the Porsche brand mind you), but you're going to go with the "might be a random spec of dirt" answer. Ladies and gentlemen I do believe we have found tonights contestant on "Please give me advise on my problem so I can ignore it!" Just sayin

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Not ignoring it at all. Just burying my head in the sand Getting ready to order some Is there any real difference in them brand to brand? I see them from $40 -$80 each

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Thank you. You beat me with a stick too often but once in a while you make feel barely adequate.

Jay, when I had the symptom, my cracks were so minor that the symptom came and went like yours every few months. After a couple years, the cracks got bigger to a point where the CEL was coming on more often. That's when I decided to investigate further and found microcracks which were still big enough to trip the CEL light and replaced all of them. I'm not saying this is your situation but don't be surprised if it doesn't manifest itself for a few months or so.

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Just so it is clear, if I was going to throw parts at the symptoms I'd throw coils before injectors. Replace all coils. Be sure the plugs do not need changing. That is if they are due (or "close" to being due) on miles -- or time -- you can kill two birds with one stone. Be sure you take extreme care and pay close attention in changing the coils. The coil's connection to the plug and the wiring harness are of course critical to the plug's proper function and the coil's proper function. Too many times after a plug/coil job misfires remain and this is traced to an improperly installed plug -- generally loose -- or an improperly installed coil.

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The plugs have less than 15k on them and I am replacing coils

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The fact that you enjoy putting long, cylindrical objects in inappropriate openings does not make it sage advice for others.

Jay, I'd consider waiting until the issue crops up again before trying to solve it. Troubleshooting an intermittent issue when it's not currently present is a great way to burn money...

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Well, I hope it works out for you. It is tough sometimes to know what to do. One wants his car running optimum to be sure but these intermittent symptoms can be misleading. While 75K miles is not that many miles the coils are probably closer to the end of their life than the beginning so it is not like you are throwing money away replacing "like new" parts.

UPDATE I replaced the coil packs even though there had been no more codes and no misfires logged with my durametric. I got Beru ones from warehouse33auto.com and with the 10% rennlist discount they were ~$35 each including shipping FYI, the new ones are thicker at the mounting bolts and come with longer bolts. The old bolts were hex cap heads and the new ones are the reverse spline e-socket ones. Not a big deal unless you don't have the e-socket I did test them for resistance, all were good and inspect them for cracks and none were found even using Paul's microscope Probably as Macster had hypothesized, a bit of crap in an injector that cleared its self