986 Boxster misfire?

I am currently 50 miles from home at 8:15 in the evening, and my Boxster ran perfect all the way here until I pulled off the freeway, then started misfiring badly to the point the check engine light flashes when I accelerate.  Any ideas what it could be? I'm guessing not something I can fix on the side of the road, and I need to call a tow truck, but I figured it doesn't hurt to ask.  I can't really be too mad because I know that's expecting a lot of an old German car, but also I have done the same with diesel Mercedes in much worse condition for years and never needed a tow.

In reply to Tk8398 :

Is it wet out and do you have the original splash shield? Checked the coil packs and boots for cracks?

It is not wet out at all, I'm not sure on the splash shields but I don't believe they would have gotten wet.  I will definitely inspect the coil packs but probably couldn't get one quickly enough to avoid just towing it home to do there.

Well I let it sit for about 3 hours and started it again and it runs fine and no check engine light.  Nice to not have to wait for a tow truck but also idk how much use a car is that you can't take farther from home than you want to potentially have it towed and don't need to be somewhere at a particular time.  I hate intermittent problems.

Three hours.. I figured you DID wait for the tow truck then tried to start it just because "why not?"  

I'm going to guess the problem will come back.  Is this the first time it happened?  From your description, something is getting hot and doesn't like it.  Maybe a coil pack?  Can you pull codes from it?

I may have a spare coil pack. Do you know your part number?

I was already where I was going so I figured why not wait until I was done to call a tow truck and I tried starting it first and it was fine.  I drove it all the way home with no issues, and there are no codes and all the emissions monitors are complete.  This has not happened before, I put about 3k miles on it with no problems, but yeah I'm sure it will happen again.  I will check the coil packs this weekend.

Unplug your coil packs carefully. I broke the locking tab off of one on my first Cayman. They are subject to a lot of heat and get very brittle. And unfortunately, they are on the plug side, not the coil pack side. 

Interesting, I guess I will have to pull the coils and test the resistance? It's not just a Porsche thing but I sometimes feel like cars of this era are a waste of time, like a VW beetle would need spark plugs and wires, distributor cap, points, etc and then you could be reasonably sure it would work for a while and quickly fix it if it didn't.  This car isn't even that new but has so many potential failure points in just the ignition system that are made out of very expensive brittle plastic that it's never going to be better than "it currently works but who knows about driving it longer than you want to have it towed from" at this point.  I feel the same about pretty much all mid 90s and up cars though.

If the check engine light was flashing there should be a code or codes stored.  You might need a real scan tool that speaks Porsche to access them but they should be there.

Are there Porsche scan tools available for less than the whole car cost that aren't as sketchy as the Mercedes ones that you need a whole separate computer for? 

It's not any real hurry to decide what I'm going to do but I'm not even sure I want to bother with fixing this, it's fine to drive when it runs but I very much hate working on it and it's apparently not really usable as a real car.  

I think coil packs are a well known issue on Boxsters and Caymans.  Not a hard job to replace them; when I did it on my Cayman I used some kind of aftermarket ones and one of them turned out to be DOA.  Use OEM if possible.

In reply to Tk8398 :

I bought the cheaper scan tool from Pelican. I forget the name but it sounds German even though it's Chinese. I got it for one purpose, to reset the oil light, as its advertised to do. After multiple attempts, it continued to fail. Many similar stories online. I sent it back and Pelican gave me full credit towards the Durametric thing. 

I bought an ICarSoft POR-2 scanner off of Amazon and it worked perfectly on my 981 Cayman.  Even had service modes to bleed ABS, etc.

In reply to Tk8398 :

It sounds like you really don't like this car and no amount of anything is going to change that. You'll probably be happier selling it and getting something that does bring you joy.

The connectors to the coil packs should "click" into place. That is the first thing I would check. Even at the factory, the connectors don't always get pushed all the way together until they click, which can result in the flashing warning light years later. 

Javelin said:

In reply to Tk8398 :

It sounds like you really don't like this car and no amount of anything is going to change that. You'll probably be happier selling it and getting something that fits bring you joy.

That's true, and not really the fault of a 23 year old high mileage Porsche but a car that I can afford, have the skill to keep running and accelerates/corners/stops well enough to drive on the freeway safely here are not the same car.  So I may do that but will probably end up still being annoyed one way or another.  

Yes, coils are often the problem. They do not All go at the same time, so if you can read a 'pending' code that isolates particular cylinders that will help.

Also possible misfire when on a long drive, then running fine after a cool down... Aging fuel pump or relay. Crank position sensor starting to fail.

This was not the smartest idea I know, but I decided since it was far cheaper than any kind of scanner that will read the codes to just change the coils and crank position sensor since they were original parts with 20 years and 150k miles anyway, so I did and now the car won't even start at all.  So I guess the next step is to put all the old parts back on and buy a $750 scanner to attempt to see whats actually wrong.  I don't specifically hate Boxsters but I hate newer (than mid 90s) cars in general, they are so cheaply made and annoying to work on, but older cars don't perform well enough to keep up with traffic anymore and a decent brand new car is 50% of the money I make in a year (or 7-8x what this Boxster cost even including all the parts I have bought while I have had it).

The ~$750 Durametric is the standard for Porsche cars that most enthusiasts use/recommend. Looks like the Enthusiast version is running a little under $300 right Now: http://www.durametric.com/buyus.aspx
 

I have an older AUTEL MD802 scanner that works for most makes, but does not have the full depth of the Durametric for Porsche. It was about $160 5-ish years ago. The newer version should be more capable than my older one, but I don't know which particular model to recommend from their current offerings. *Probably the MD806: http://download1.auteltech.net/Download/Veh/MD808/EX/Porsche/en_MaxiDiag_E_Porsche%20FUNCLIST.pdf

Foxwell also makes a good tool for diagnostics. I am not sure what model, but I bet this forum has enough users to discuss it, or ask/search on the 986Forum.com & Rennlist.com forums to see what the current 'good' scanner is.

You don't need to spend $750.

The Foxwell NT530 works pretty well, it's what I got for my Cayman. I believe that you can get them on Amazon for about $170 right now, and they are already pre-programmed for your particular Porsche.

Porsche's are really unusual cars that aren't much like any other make. They just do things their own way. Because of that,  you will need a reader that is specific to Porsche, and possibly your model. 

If you are going to get the car serviced, don't take it to just any mechanic, take it to a Porsche specialist independent.