Misfire & engine light - 986 Forum - The Community for Porsche Boxster & Cayman Owners

Hi, my 1998 2.5 Boxster has just started to misfire (rough running) and the check engine light started flashing. I've not driven it other than to a local garage who use a Snap-on code reader. They said all it stated was multipul misfire and advised taking it to Porsche! At first I was worried about total engine failure (block gone) but then read on here that it can be just the cables to the spark plugs coming loose (I replaced the spark plugs about 6 months ago with no problems). Any ideas what it could be? Thanks. PS. over the last few months it has been holding back a bit at 5000rpm+. Like lack of fuel but I replaced the fuel filter. Could this be linked or is this another problem potenitally with some sensor?

A flashing MIL is not a good thing at all. Don't drive the car until a qualified mechanic looks it over. It could be a small item, but the flashing MIL is a warning and Porsche says not to drive the car. The cheapest thing in the long run could well be to have it towed to a qualified shop or dealership. Sorry for your trouble.

It sounds like the car went into "limp home" mode. Under certain conditions, the engine will shut down a cylinder by deactivating an injector.

Do get a code reader, $35 at Autozone/Napa. Get all the codes and write em down. Do not drive it. A flashing CEL means driving it could kill it.

+1 on not driving it and getting it towed to your trusted Porsche mechanic. Good luck and keep us posted!

Was your CEL still flashing when you drove it to the mechanic? Or did it FLASH then turn solid after the "event"? Get the car checked out & let us know what they find.

Sounds like the same symptoms I had when my Mass Air Flow (MAF) Sensor failed. You might want to search on that topic for more info. You were wise to stop driving the car. The technician who repaired my car stated that raw fuel could flow into the catalytic convertors which is a serious fire hazard. If it is your MAF, it is about a $500 repair. Not cheap, but less than a new engine. Good luck.

I just had to do a MAF last week. Save yourself some research here was the cheapest I could find. http://www.thepartsbin.com/catalog/?N=1698+11567+4294967265+9359 I got it for $250.00 Good luck and hope it turns out to be nothing worse that this.

I went with the advise and purchased a code reader: http://talktomycar.co.uk/Shop/Code_Readers/mj004.htm It has identified 4 faults and the manual describes them as: P0300 Random/multipul cylinder misfire P0301 Cylinder 1 misfire P0302 Cylinder 2 misfire P0303 Cylinder 3 misfire So its given a good direction to the problem but I don't know which cylinder's are 1,2 & 3 as I sit in the drivers seat? Also, I'm not really sure what to check other than the wires for the spark plugs? Any other ideas? Thanks.

Cylinders 1-3 are bank 1 which is on the right side of the car. If you have a RHD then it is the drivers side. Check to make sure that the connector to each coil is connected properly. You also might remove the coils and check for cracks.

Only misfire codes? No sensor codes? Problem is in bank one. I suspect something is still missing. Usually you will also get a too rich/ too lean code that identifies the problem. Do a code search on Renntech.org for further details and things to look for. Any recent service/modifications done? Recently blast through standing water that may have soaked your coils?

I've taken the coils off 1,2 & 3 cylinders on the right side of the car (as you sit in it). I found nothing wrong at all. The clips holding the wires in place are all fine and there is no oil in the spark plug tubes? I drove it down the road but still same problem - holding back a lot and very lumpy. The Engine light is still flashing but does go constant when not at idle. Only other think I did notice was that there is a bit of oil on the sump. Not really enough to even make a mark on the ground but its very difficult to see where it could of come from. I'm now starting to get very worried!

I vote MAF

Pardon the ignorance, but wouldn't a MAF error cause missfires to BOTH cylinder banks? Methinks you need to get a Porsche Scan tool to download ALL codes. It was suggested to me that some of the "over the counter" scanners are not always adept at extracting Porsches' information. Case in point was a local "european" shop code reader could only tell them that "something was wrong".. The independant Porsche shop with the Porsche tools and know how was able to pinpoint the exact part failure and correct the problem.

Well, I took it to an independent dealer today and their computer provided more detail than my generic code reader. It did state that the cam position sensor was incorrect. So they are replacing it - about £100 for the part & up to another £300 for time. They seem very good and I hope it works!

you can get a flashing CEL because you left the gas cap or oil fill cap off (or not properly sealing). there's even a sticker behind the gas fill flap that says this.

Glad to hear a diagnosis was made. Ideally the correct one. That PST2 or whatever Porsche calls it is much better than the generic ones. The same shop that solved my issue (a failed variocam actuator) has had several clients who have replaced MAFs thinking that was the problem (due to the generic code reader) only to learn it was other things wrong with the cars.

I bet you are also getting a code of P013something.. This wil say that you have a bad O2 sensor on the 1-3 cylinders (passengers side). I know, I had all the same codes till about 2 hrs ago.

Sounds like you are on the right track. A pocket code reader is good for about 90% of DIY diagnosis and fixes. There are times when there is no substitute for a qualified and experienced Porsche repair shop. This is one of those times. Good luck with your car.

I plan on getting the exact codes tomorrow from the dealer but after having these exact problems, he said I had a general misfire code and to replace all coils and spark plugs. I told him to catch fire and I would register on teh 986forum and get some real research! Be back tomorrow with exact codes!