Ah, maybe I'm thinking of older years; much older (pre-digital control,) or for racing applications.

My 1999 2.5 Box wouldn't rev past 5500rpm and missfired today. I plugged OBC reader in and got the codes: P0300, P0304, P0305 & P0306. The car has done 90k miles. I have not yet changed the MAF sensor. Do these codes point at this sensor? Am I OK to still drive the car while I find the cause?



Edited 1 time(s). Last edit at 04/10/2011 05:04PM by marty. (view changes)

are what the 304/5/6 are usually saying and 300 just saying it is happening a lot and could pour raw gas into the cats and damage them.

All on one side of the engine...the drivers side on a US car.

Done anything to the car recently? Run the gas tank dry?

The only recent thing was I had the joint between the exhaust manifold and the CAT flange fail. It was prob. blowing slightly for weeks, then went LOUD! I fixed this straight away then.

This was on the US passenger side of the car.



Edited 1 time(s). Last edit at 04/11/2011 05:08AM by marty. (view changes)

transistory, there one instant and gone the next. At startup sometimes (my experience in my two cars) but others have reported misfires during a hard run (like on the track). If they appear at other times this suggests a pretty hard failure, of at least the coils. (MAFs have been known to cause misfires and on one bank, too, but this is rare. I encountered one instance of this that someone reported misfires on one bank and after trying a few things replaced the MAF and the symptoms went away.)

In your car's case even though the check engine light is on as long as it isn't flashing (or doesn't begin to flash) and the engine is otherwise running ok you're ok to continue to drive the car, but really this just means you're ok to drive the car to someplace and have the symptoms looked into and dealt with. If this means home to your garage or to a dealer service department or a qualified indy shop that is up to you.

And if at anytime during this drive home/to the shop if the CEL begins flashing or the engine starts misbehaving or making noises, turn the engine off as soon as you can. The engine is sick and the less running it receives the better off it will be and the better off you'll be. No truely sick engine ever got better with more running.

If the engine's running ok now clear the codes and see if they come back. You might check that joint between the exhaust flange and the converter to see if there's a leak there. Last thing touched and all that...

Hard to recommend a coil/plug job without more evidence it is needed. 90K miles for plugs is about 30K miles too long (IIRC the plug change interval for Boxsters). Coils with 90K miles might be just entering middle age or they could be past it. Depends. In some areas (UK at least) coils are nearly a yearly maintenance item. In other places (CA maybe, southwest?) they're a lifetime component. (My 02 is on its original coils and has over 241K miles, though the engine did experience a misfire problem some weeks back after I started the engine after it had sat a while (couple days) in wet/damp weather. So they're probably due to be changed.)

Another 'trick' is to after the clearing the error codes disconnect the MAF at the wiring harness and drive the car and see if the symptoms come back. This can eliminate or confirm the MAF is the cause.

Sincerely,

MarcW.

I have purchased and fitted six new coil packs and spark plugs today, and cleared the error codes with my reader.

I will let you know if this cures it.

My local independant guy put his Porsche laptop on the car and got the same codes as my reader. He says coil packs regularly crack and fall to bits! Fingers crossed now!

sounds a bit odd.

Wish you luck.

At least on the passenger's side if the car's a USA car. This side sees more splash and such when the car is driven in the wet because as you know often the shoulder or curb side of the roadway has standing water and this water is not clean. Thus the coils on the passenger side are subjected to a more frequent splash of water and the water is generally of the nasty sort.

Not sure I would have replaced the coils/plugs without more proof -- maybe spraying a warm engine's coils with a spray bottle of saline solution water and lettng the engine sit a bit before starting the engine to see if the misfires return upon this restart-- but if the coils were original and the plugs due to be changed... it is a good step. I hope for the OP's sake it proves to be the last step because it solves the problem.

Sincerely,

MarcW.

Om my '05 987 I replaced the plugs about a year ago (with a post at ppbb) and it was a simple job. Recently, I had the car into the dealer for a warning light on the coolant and I had a hard time starting the car on the day I took it in. The tech said that the plugs were badly worn and the coils were cracked. So I got 60K out of the original plugs, but only 15 out of the replacements - I suspect that the coils were getting bad when I did the plugs, but I did not notice, and so they have run with poor coils and gotten themselves into bad shape.

Does that make any sense? or should I look for another explanation for the plug wear.

Quote
TheFarmer
Om my '05 987 I replaced the plugs about a year ago (with a post at ppbb) and it was a simple job. Recently, I had the car into the dealer for a warning light on the coolant and I had a hard time starting the car on the day I took it in. The tech said that the plugs were badly worn and the coils were cracked. So I got 60K out of the original plugs, but only 15 out of the replacements - I suspect that the coils were getting bad when I did the plugs, but I did not notice, and so they have run with poor coils and gotten themselves into bad shape.

Does that make any sense? or should I look for another explanation for the plug wear.

Generally if the coils are bad they don't spark the plugs as energetically as they would otherwise and this works to lessen spark plug electrode errosion. The engine runs sometimes poorly but maybe not poorly enough to be noticed if the degradation takes place over time and no other symptoms appear.

Assuming your tech's diagnosis/opinion of the plugs was accurate I would agree with Laz's opinion and suspect the wrong plugs were used.

I had the plugs replaced in my 02 Boxster after more than 60K miles and while there was some obvious errosion of the electrodes the engine didn't seem to perk up any after the plug change. The old plugs were Beru ultra R6 336. I assume that is what the tech put back in my car's engine.

Other factors might be usage -- high speed/high rpms can accelerate plug errosion. Another is the brand of gas you put in the car's gas tank. I assume you've always run a name brand gas of the proper octane grade and bought from a busy station?

If the intake/exhaust system stock?

Sincerely,

MarcW.

different plugs for the Boxster or the Turbo.

Sincerely,

MarcW.

Alfas had two different "Golden Lodge" plugs specified. They're nice looking, with four ground electrodes.

plug that he used with the belief it gave him an edge over everyone else.

Nowadays with modern cars (at least Porsches) with their accurate fueling and extremely high spark plug voltages plugs have an easier time of it. (And no lead!)

Given how well these engines perform 'stock' I don't think Porsche left anything on the table regarding spark plug choice.

My belief is using the recommended plug and changing them at the recommended interval is all the plug science I need to know.

Sincerely,

MarcW.

it was running as rough as guts and even stopping and it was "spitfire" a petrol/gas additive that solves it every time.....i gather a cup of metho in your tank does the same but Marc W will know

or water in the tanks. I'm not even sure what is available. Many recommend Marine Stabil for helping keep gas from going off for vehicles stored part of the year but if this stuff can address bad gas or water in the gas I have no idea.

The only gas tank additive I use is once in a while (every other year or so) is a bottle or two of Techron to clean out the fuel system and help remove deposits from the engine in preparation to having my Boxster tested for emissions.

When the tech replaced the fuel pump in the Boxster (at over 200K miles) he found no signs of any water in the tank and the amount of trash was quite low. There was a bit of trash caught in the fine mesh of the fuel pump intake screen -- the only fuel filter the car has. And this trash was removed from the tank when the fuel pump was removed.

Sincerely,

MarcW.

If there are different specs, you would think that the computer at the parts department would pull up the right ones. I am inclined to suspect the coils, but then the question becomes one of how to inspect/test the coils when servicing the plugs.

parts. The parts lookup system at the dealer is designed to accept the VIN. This is the best assurance you are getting the right part for your car or your car's engine.

Sincerely,

MarcW.