P0304 and P0443

[CleanNeon98]

Car: 2004 Mazdaspeed Miata 43k miles

Issue: (3)P0304 and (1)P0443 CEL lights

Yesterday
What happened:
OK so yesterday I am driving to work and all of a sudden I notice a CEL on. Go after work and get it checked, car comes back with (2)P0304 codes and (1)P0443. For those who don't want to look them up

P0304 - Cylinder 4 misfire
P0443 - Evap Purge System <-more on this one at the end

Car's behavior:
Misfires only occur at idle (800rpm), behaves normally under load. Misfires are totally random, there could be 5 in a row within 5 seconds, or sometimes there will be one, then 10 seconds fine, then 1 more..sometimes 3 more...etc.etc. Cleared the codes and thought it was just random.

Today
What happened:
Driving to school today, stopped at a light for a little while, CEL comes back on. Come to Advance Auto after class to get the code(s) ran, comes back with (1)P0304, same cylinder 4 misfire.

Car's behavior:
Misfires only occur at idle (800rpm), behaves normally under load. Misfires are totally random, there could be 5 in a row within 5 seconds, or sometimes there will be one, then 10 seconds fine, then 1 more..sometimes 3 more...etc.etc. Also noticed that if I sit at a light and hold the RPM at ~1,500 or so, I can feel it misfiring very slightly and only through the shifter. If at idle the misfires are strong to the point where it feel like someone keeps tapping you in the back bumper.

Solutions?
All of this leads me to believe I have a bad coil pack on cylinder 4. I think that if the spark plug was at fault the misfires would have been more consistent and drivability would be affected. Furthermore, a search on Miata.net revealed quite a few similar issues with misfires caused by coil packs. It seems like it has something to do with the voltage going to the coil pack that makes it act weird.

As far as code P0443, I have no idea what it is. When scanned today, the code did not come back. Searching on miata.net revealed 0 similar issues with any other cars.

What should I do about this mess?

[Elliott18t]

P0433 Heated Catalyst Efficiency Below Threshold (Bank 2)

http://forums.mazdaworld.org/index.php?showtopic=8970&hl=1412


??

[CleanNeon98]

P0433 Heated Catalyst Efficiency Below Threshold (Bank 2)

http://forums.mazdaworld.org/index.php?showtopic=8970&hl=1412


??
Sorry, I meant P0443

[Elliott18t]

This guy on a bimmer forum got the same code.. possibly not the same but since its a generic code it may help

The PCM has determined that a malfunction exists in the electrical circuit for the purge control valve in the evaporative emission control system.

Definition
EVAP (Evaporative Emission System) purge/vent solenoid circuit condition

Explanation
The solenoids and system wiring are monitored for opens or shorts

Probable Causes
1. Purge or vent solenoids defective
2. Check connector and wiring
3. Fuel saturated vapor canister
4. Failed EVAP vent solenoid


ive also seen other people with this code being told to check the gas cap.

[CleanNeon98]

Ill check it out.

Also going to start checking stuff now. Will pull the plug and coil pack from cylinder 4 and see what I find. If the plug is oily I may just need some new seals and gaskets which wont be bad. If the coil pack is bad, I'm looking at around $130 for a new one from a dealer, not really excited about that. Ill try swapping the coil packs between cylinders 4 and 2 and see if the misfire moves with the pack, hopefully someone has a code reader at the meet tomorrow night. Otherwise, it could be a clogged injector so I am going to add in some fuel system cleaner w/ octane booster tomorrow when I get gas.

There isn't much more I can think of.

[justinlansdale]

i had misfire codes when my plugs went bad, changed the plugs and regapped; problem remained. thought it was the coilpack, wasn't the case. turns out it was the plug wires. don't overlook the wires!

[CleanNeon98]

i had misfire codes when my plugs went bad, changed the plugs and regapped; problem remained. thought it was the coilpack, wasn't the case. turns out it was the plug wires. don't overlook the wires!
Weird...how much were the wires for your car so I have some kind of feel for it?

Also, I am running Bosch Platinum plugs, when we put them in, Denso Iridium came out...could it be that these plugs just aren't meant to be used on this car?

[CleanNeon98]

Pulled the plugs, they look fine. Swapped around coilpacks between cylinders 2 and 4, still misfires. Cleared the CEL so I'm not sure where it's coming from but hopefully it comes back by tomorrow night so I can track it down.

[Ciotti]

Bosch Platinums are AWFUL when used in SN-95 Cobras, I switched over to Autolite plugs and the car pulled noticeably smoother and quicker through the revs.

[CleanNeon98]

Ill probbably get new plugs either way then...might just do that today and put them in quickly before it gets dark out. The car ran fine when I put them in though, but now that I think about it, idle has been slowly getting worse..cant remember if it was just recently or since the plugs. Part of it is also this.

After putting the intake on, sometimes the RPM would just dip and then jump back up when at idle...maybe I should look into the intake? I doubt it would be causing misfires though, especially on one cylinder.

[Elliott18t]

id go back the some densos or NGKs

[CleanNeon98]

I think I figured out what the other code is. Some time ago I was trying to tighten some suspension parts and I didn't have the right tool to reach so I had to unplug some stuff to get a wrench in there and then I forgot to plug it back in when I started the car and had a CEL for a bit. The light turned off but I guess it stayed in the memory registry of the ECU or something.

Im just hoping for the light to come back by tomorrow night so I can make progress with this :(

[CleanNeon98]

A bad coilpack doesnt make sense though. Here is a small drawing.

http://img155.imageshack.us/img155/3228/51134280xc0.jpg

Basically cylinders 2 and 4 have the "master" coils represented by the solid boxes. Then they branch out to their corresponding cylinders (2-3, 1-4). If the coilpack that was on cylinder 4 was bad and caused cylinder 4 to misfire, wouldn't cylinder 1 misfire as well, since they are both controlled by the same pack, or did the ECU only register the cylinder 4 misfire because its closer to the source?

[Elliott18t]

i think justins car is the same way and he had a misfire on one of the cylinders i believe. said his wires where bad.

[CleanNeon98]

i think justins car is the same way and he had a misfire on one of the cylinders i believe. said his wires where bad.
Just googled it and you are right..wonder what he means by wires, the extensions or the harnesses...weird thing is that there is no "wire" leading to cylinder 4 it has its own pack so i dont know how a bad wire would cause it to misfire. Well the wire leading to cylinder 4 comes out of some large harness...don't wanna touch that too much haha

[justinlansdale]

my car is set up the same way, i have two coilpacks; one pack on cylinder 2 and one on cylinder 4, it could be an issue with the plug boots on either of the coilpacks, there is a small spring between the plug boot and the coilpack, make sure that the spring is evenly set in the boot, that could cause an issue also. i would also recommend sticking with OEM mazda ignition components because thats where my problem lied to begin with. i bought new ignition wires and boots from mazda and all my problems went away. also, i'd definitely run NGK iridiums, and gap 'em smaller if you plan on running more boost.

[justinlansdale]

Weird...how much were the wires for your car so I have some kind of feel for it?

i don't remember exactly how much they ran me but i want to say around $70 bucks?

[CleanNeon98]

Maybe I can get away with just putting in normal plugs then and not have to replace anything else.

[Loserkidwac]

Yea I had a similar problem on my MSP turned out to be one of the coil packs...I think I was getting a multiple cyl miss fire code though...I think the wires were fairly cheap from Mazda...the coil packs were about double what I paid for at the parts store...

I also suggest Denso Iridium plugs...they have worked the best in my MSP out of any others...I had to order them online since most parts stores didn't carry them and wanted more $$ for them anyways...oh I'd also get some automotive electronic cleaner spray and clean the plus on the coil packs...could be a chance maybe there is some corrosion or dirt on them or the harness plug...

[CleanNeon98]

Is it OK to order the stuff and drive the car for now or should I let it sit? I don't want to cause any engine damage..someone told me I could ruin my catalytic converter, if he meant hollow it out, I really wouldn't mind it lol

[justinlansdale]

i don't think you'll have a problem driving it the way it is now, i drove my car on shot plugs misfiring everytime i hit boost for a few days before i had the chance to get the new plugs and what not.

[Loserkidwac]

You could potentially damage the cat..not hollow it out bug clog it up...you're going to have extra unburnt fuel since you are having a misfire, plus with a CEL your car is probably in limp mode and dumping fuel as a precaution...I'd be cautious but you can still drive, just try to limit it...

[Elliott18t]

or you could go no cat and have a CEL all the time from the down stream 02 sensor :P
( i dont know if mazdas work that way though )

[CleanNeon98]

Well once the CEL comes back Ill scan it again...will put in different plugs regardless of what happens.

[Kevin S]

Yea def see if the misfire moved cylinders after switching the coils. In most cases if it occurs at idle and goes away under load it is a fuel/injector problem, ign misfires will get worse under heavy load. Put it in a high gear @ low rpm and put a large load on it(uphill or pull up on the ebrake alittle) and see if it stumbles.

If it does chk the coil boot for carbon tracking and excessive carbon/worn plugs.

Could also be other things then fuel/ign such as a vac leak at the intake gasket.

[CleanNeon98]

Now I got code P0302. Gonna do a resistance test on the packs tomorrow, and check them thoroughly. Also putting in the new NGK Iridium plugs tomorrow. I put in new gas and Lucas Injector cleaner and immediately the problem seems to have lessened but it's still there. Now that I think about it, someone told me a long time ago that they thought the car was misfiring at idle because they put their hand behind the exhaust and felt it kinda pop, so yea...just hoping this doesn't cost me too much.

[CleanNeon98]

OK, after all of the worrying I think I finally fixed the issue. Took out the old plugs and thanks to justinlansdale's advice, I took the gap down from .035 to .030 and it seems to have fixed the problem. It also seems to have made the car run much stronger, builds boost smoother, better idle, just makes the engine run so much better. Additionally, the plugs were gapped unevenly, anywhere from .035 to .037 on all 4 cylinders. Still going to install the new NGK plugs tomorrow, but I'm glad the car is running better, drove about 50 miles tonight for various meets and not a single misfire at a light whereas before it would miss anywhere from 1-10 times.

Will update.

[justinlansdale]

yay, good deal. glad you got the problem fixed and hopefully it'll stay fixed haha.

[CleanNeon98]

Yea, I figure if it isnt fixed the CEL will be back by mid next week.