P0306-misfire

[akcamaro02]

my car has been acting very rough at idle, and when taking off for at least a month now. I've just ignored it to this point because it wasn't too extreme but today when I was pulling up in my driveway, it was extremely rough, almost to the point it died and the SES light was flashing at me so I shut the car off immediately. I have OBDwiz on my laptop so I hooked that up and got a P0306-cylinder 6 misfire code, which immediately went from pending to stored, less than 5 seconds.

I'm not an expert on engine codes and what not and since there's a whole laundry list of things you could try and fix for a misfire, I'd appreciate any help diagnosing this problem. On a side note, I have been getting really bad gas mileage over the last month, the exhaust sounds very chug a lug lug at idle, almost sounds like an exhaust leak or like there's paper in the tailpipe, the idle is very rough, especially noticeable when slowly letting off the brake.
Most of the problems are way worse when the car is in drive or reverse.

Car is an 02 with about 106xxx miles.
I don't think it's a plug or wire. I replaced them within the past 2 years.
Cat is aftermarket high flow, just got put on maybe little over a year.
I don't know what other things I could easily test myself. Like I said, I have OBDwiz, which gives me a lot of fuel information, air flows, o2 readings, etc. if that would help diagnose anything.
Please help.
Safe to drive in the meantime or let it sit?

[ssms5411]

Re: P0306-misfire

I would still check the plug wire and maybe the coil.

[akcamaro02]

Re: P0306-misfire

I just unplugged the plug wire from number 6 and made sure it was fully connected. Started the car and let it run, still have the code(which i know won't go away immediately), but the symptoms didn't clear up any.

ignore the different sound in the exhaust. I got under there and there's some small holes in the muffler, appeared to have rusted through.

how do you check the coil packs?

[MegaHertz]

Re: P0306-misfire

swap the coil pack for #6 with one of the others. If the code moves to a different cylinder its probably the coil pack.
edit: rephrasing

[akcamaro02]

Re: P0306-misfire

couldn't I just plug another wire into the coil pack and see if the code moves to that cylinder?

[MegaHertz]

Re: P0306-misfire

no the timing would be off for the spark - you have to actually swap the coils. On that note - make sure all the wires are plugged into the right coil. (if wires were swapped you'd probably be getting multiple cylinder misfire but better to check) - you don't need a new coil - just swap with one of your existing ones. They are not hard to remove, 1 bolt or nut for each and the wires.

[akcamaro02]

Re: P0306-misfire

ok, so keep the same wires hooked up to the same cyl number too then?

[MegaHertz]

Re: P0306-misfire

Keep the wires in the same order front to back. Just swap the front pack with the middle one. Put the same wires that are in the front pack back onto the middle pack that you swapped in. Cylinder 6 (pass rear) is always the front most coil position. Cylinder 3(driver middle) is the next one on the first pack . Doesn't matter where the coil pack is as it is the wires that always have to be hooked up in the right order. The coil packs just amplify the voltage of the spark signal they are given. http://autorepair.about.com/library/...bl-fo-3655.htm

[FIREBIRDV6RAGE]

Re: P0306-misfire

this is what i would do , first check if its connected right no corrosion or anything after that if its all good then check if you are getting spark from spark plug number 6. if you are getting spark then next thing up is to see if you are getting enough fuel or any at all at cylinder number six. if your not getting any spark it might be the coil pack as mega and ssms said above. if the occasion that you are not getting any fuel then check the fuel injector, it might be faulty or maybe a wire that is connecting to it is just cut or not even connected.

[akcamaro02]

Re: P0306-misfire

is there anyway to tell a fuel issue from my laptop? I have OBDwiz on it, it has fuel spec readings and such on there..

[akcamaro02]

Re: P0306-misfire

i'll try the coil packs first, but it's much easier to plug in the laptop than to swap coil packs. just trying to think smart, not hard.

[ssms5411]

Re: P0306-misfire

If it can monitor the injector readings see if the #6 injector is working right.

[akcamaro02]

Re: P0306-misfire

it says it can monitor
0x06 Short term fuel % trim - Bank 1
0x07 Long term fuel % trim - Bank 1
0x08 Short term fuel % trim - Bank 2
0x09 Long term fuel % trim - Bank 2
0x0A Fuel pressure
0x2F Fuel level input
0x51 Fuel type
0x5D Fuel injection timing
0x5E Fuel rate

That's what it claims it can read. I'd have to plug it in to see if it actually gives a reading for all of them.

Fuel injection timing??

[MegaHertz]

Re: P0306-misfire

If you can monitor that stuff do it, see what changes when you change the variables. You can monitor all you want, but when you start changing/testing things is when you will see progress.

[thebeewantsboost]

Re: P0306-misfire

i hear hptuners has a program in alpha testing that will self diagnose and change out bad parts. maybe by the beta phase it'll be able to swap in a built transmission for me :D