Misfire on 4 every 500 miles

Ask Bimmerforums who recommended Pelican Parts who recommended you fellas. Here's the downlow: 2002 w/ 57,000 miles. It is not the coils, plugs have been replaced. This is the third time it has happened, all three times it has been at 500 mile increments. Not the gas cap. First time changed the plugs, swapped the coils second time, same cylender so not the coils, tightened up small oil leak This time it happened 400 miles away, and the car is at a shop I do not trust. If it were me, I'd just drive it home, but it's my mom and she won't. I would like ideas on what it is so I can have some education and I can call BS if needed. Thanks. Best advice I've recieved so far is that it may be the air mass filter.

Were the coils replaced or just switched around. Coils are cheap to replace $50 each and with that year and mileage I would not be surprised if some where shot. You didn'y say if the car is showing a CEL light or if any codes have been pulled using a OBD sensor. Any diagnosis with out checking for codes first is really just guessing. Is the mis at idle or under power or both?

Any reason why you haven't ask the dealer to take a look as opposed to having your car at a "shop I don't trust". Don't understand the logic on that one. And CEL codes?

silverbeam - you're new here, so I'll be nice - this is the most amazing forum I have joined/read - if you provide a bit more information, we can help more - where is the car now? Someone in that area will likely be able to refer you to a quality local independent person or a trustworthy dealer. If you had an air mass filter problem, it seems that you would have more intermittent problems (vs. only every 500 miles) and your CEL would come on.

The car has been diagnosed using code readers, got the code for a misfire on 4, which as I've been told is very vauge and means that it could be a number of things. The car is at Michael Porsche in Fresno. Just because it is a dealership doesn't mean I automatically trust them. I've had more trust issues with Newport than any other service center I've worked with. I am not quick to trust dealers. Also, they are working with my mom here.. a 50 year old blonde. They get money signs in their eyes when she walks in with a problem. From what I last heard from the dealer, the check engine light is off, but they haven't done anything to fix the problem. So we're looking at an intermediate misfire... the fun problems to fix. They thought spark plugs, but I told them no, they were replaced 2 months ago. I gave them the number for our shop down here (Vision Motorsports) and my number. So at this point in time they are just diagnosing the car further. Vision also doesn't think it is an AMM problem, but another Porsche tech at bimmerforums seems to think it is. What other info do you need blackcab?

Sometimes the "O" rings around the spark plug tear and let oil past and get into the spark plug "boot". Of course this grounds the plug out causing a misfire, very common.

Tippy, if that were it, do you think they would have found it when they changed the spark plugs 2 months ago?

deffiatly shold have found it when they were doing plugs, and unless im having a off day 02 is the first year of the new style cam cover with no tubes to leak. If the coils were swiched and the plugs replaced then chances are its not the coils. could be an injector but injector failure is pretty rare so id almost rule that out especailly being intermittent Definate possibilty is a lifter sticking, has the car been serviced in a timely manner oil chnages ect?

The car is maintained on time. Actually, it may be serviced too much. Last time the oil was changed it had only been in the car for 4,000 miles. We changed it because it has been a year.

what is the dealer recomending?

I don't know what the dealer is recommending any more. My mom is being strange. She gave the dealership incorrect info on the maintanace history (told them that the shop didn't replace the spark plugs). I asked her to keep me informed. She called me and told me it was the plugs. I told her they replaced them, she tried to argue with me even though I'm the one who brought it to Vision and got them changed. So I called the dealership, and told them the plugs didn't need to be replaced unless they were fouled. But she is mad at me because my instructions slowed the car down. Yeah, because having them change 2 month old spark plugs wasn't slowing the correct diagnosis down? Before all of this happened, it was my job to maintain this car. I am not even kidding, these are my mom's exact words. If it's broke, she tells me to fix it and I fix it. I try to fix it this time, because it's my job, and she doesn't appreciate it. In fact, she gets downright mad at me. I should have told her it was not the plugs instead of slowing the dealer down? Sorry but I DID, you didn't believe me. So, the dealer can do what they want to do. My mom can pay what ever they want. I am not offering any more suggestions to her, or the dealership because she obviously doesn't want me to. Thanks to everyone for their help.

As 99firehawk said, the 02's changed configurations and I didnt realize that, this info on "O" rings came from a service manager that told me this is a very common problem and what was the problem with my misfire. Sorry for the error.

I had the exact same things you're talking about going on with my car. Flashing CEL, misfire on #4, changed coil, repeat - changed plugs, repeat - moved coils around, repeat - PCNA decides to replace engine. This happened to me at about 5,000 miles. They eventually found metal in the oil filter, and really came up with no clear explanation what was going on, or the reason there was metal in the oil filter. They did absolve me from any abuse. I have never had an over rev, and the car was broken in according to the instructions. I was lucky mine was under warranty. I am not saying you are going to need a new engine, but simply saying I had pretty much the exact same symptons you're experiencing and their solution was engine replacement.

This is ridiculous... Engine replacement??? It seems like engine replacement is the solution for everything with the 996. I think it is a dealer excuse to not find the real problem.

metal in the oil is major, being Porsche it is no surprise they would replace the motor

More and more car companies are going with component replacement rather than a break down, analysis and attempt to fix. I personlly would rather have a new engine off the shelf that have someone try and remachine a cylinder casing or something. They are already making the engines anyway. BMW is doing the same thing. They will pretty much replace headers and a few other things, or they simply go with replacement. It won't be long before they are doing this with suspension and other things as well. It becomes cheaper to unbolt on and bolt in another than paying someone to break down engines and try and patch them up.

The dream of Tucker, realized!

Tucker was a great car