Help I need insight on a p0300 code and a few others.
 

I have the CEL on and I took the car to have codes pulled. I got a P0300, U0121, U0167, U0101, U0155, and U0100. From my understanding the U codes are can happen when a one of those generic code readers are used to pull the codes. The P0300 is the random misfire code which could mean plugs, wires or coils or vacuum leak/ faulty injectors, or fuel pressure issues. Well the car last had the plugs and wires changed at 49,000 and the car now has 62,000 miles. Would it make sense for me to go ahead and change the plugs and wires again or should I take the vehicle in and just have the dealer run a diagnostic? I have an extended warranty that covers everything but the pulgs and the wires. How long is the warranty on on parts like the plugs and wires?

Hi,

Hope you have sorted your problem, but if not, i would take a look at the coils, as you have only just done plugs and wires.

I have had the same issue recently and found 2 coils in a bad way (scorch marks and pitted marks), the scorch marks are normal as the coils get hot, its the small circular burns that are the problem - once i changed the faulty coils and had the faults re-set - problem solved.

There may be other issues but checking the coils is something you can do yourself.

There are a couple of good threads in the DIY section.

Stay away from the dealership for diagnostics.... unless you want to give me 100 bucks because you've got money to burn...:)


If you're in the US, you can have your codes read with a proper code reader from autozone or other auto parts store.

With the codes you can find out what exactly they mean on the forums. Search it.
You miss may not be ignition related (but lets be honest, it probably is)

With a mis-fire... I would say start with the plugs... but since those are only 13k miles old.... I would start with the coils. (Good call Kissies)

If problem persists, then do plugs and wires again. If that still doesn't help... well, you'll have more information by then and just keep everyone updated.
There are a ton of smart people on here that know the 8 inside and out.

Had a "track day" modified because of the same issue (P0300 code, flashing CEL). Engine would pull like a freight train until 4th gear WOT around 7500 RPM, then you could feel it stumble and on came the CEL. Thought it was olddragger's low fuel problem, so next time out the tank was topped off. Same damn thing. Got to talking to Eric Meyer's sponsor at VIR about the fuel tank issue, he said it shouldn't provoke a straight-line misfire (but the stock tank design does suck from a cornering performance reliability point of view)

New plugs have 840 miles on them.

She's a 2004 base model. Car is on the 2nd engine, 51k total miles with 35k on this engine, I am 2nd owner, and my local dealer is giving me bullsh!t about charging for the MSP16 update / engine test.

I don't need this crap.

Start with the coils / wires? Going to be hard to replicate the conditions under which the problem shows, since I can't see the Caroline Co. police allowing a 4th gear pull to redline. :uhh:

sorry to bring out an old thread, but I have a '06 rx8 gt. same problem, engine light came on at about 42,000 km's, and just recently my car cut back to one rotor at 53,000 km's. I changed my plugs and wires, no difference, then order a "coil pack" but only received one coil. but all 4 coils are pretty bad, just waiting on the other three now. if it still runs the same, what else would cause it to run like so?

Bump. Also would like to know ^^

...Can someone help me? I'm extremely new here and I need some help. I have a 2008 Mazda RX-8 Touring, it has 85,700 miles on it. I have the following error codes: P0300, P0506, P050A, P0302, P2004. I've replaced the upstream o2 sensor, all 4 spark plugs, and replaced a coil pack with a new one. But still got those codes. Any ideas? I've been reading all of your guy's stuff and its helped me get this far, just I need more of it and figured I'd just try to be specific about it.

Don't replace just one coil. Replace all 4, at the same time as you do plugs.

Read the new and potential owners thread found in the new members forum.