BigCajun

iTrader: (1)

I hope they did much more than that for $3400.

AlexVarela

Well BigCajun i bought a new ignition system BHR + BHR Midpipe + new starter + new fuel pump assembly + New clutch pedal (replaced for free by warranty) and Edelbrock Stainless Clutch Hose Kit. not including labour. So i got a lot of parts as well, even though it was a little expensive for that particular vehicle but still i love that machine.

BigCajun

iTrader: (1)

Oh, now I understand.
I thought the dealer charged you $3400.

Jcola

hello everyone I have a bit of an issue with my cel blinking which I know is indicating a misfire.




skip this if you don't care about the history
so here is the lay down of everything that has happened with this particular car. I bought it 6 months ago with a blown engine, 2004 MT. I originally wanted to rebuild it but the core was to far gone for my budget. So I had gone ahead and ordered a used engine with around 58k miles on it and put it in the car. It took a little finagling to get it going on first time start up but none the less its running. Now a week later the car is running fantastic, has good pull even at low rpm, running through the gear feels fine, revs feel butter smooth into the high rpm range, and it idles like a dream.


problem and details
here is the issue is that at low rpm around 2500 rpm it reads a misfire and now cel is constantly on for p0300, I check the codes with my cobb ap and that's all that is shows and running on mazdas oem stock map.

Rich smelling
it also smells to be running really rich but does not backfire while driving. while sitting still reving it'll have a backfire here and there though but nothing that seems major.

catalytic converter
also the cat in this car(2004 MT) is not oem the people before me cut out the mazda cat and welded an aftermarket cat in place of it. I assume the O2 sensors work fine cause im sure id get another cel code if they weren't.

Engine
the engine i ordered was imported from japan, it did come with an ecu but im using the ECU the car originally came with the ecu has taken to the imported engine well other then this odd misfire and it being rich afr.

Coils and spark plugs
the coils are in good condition, basically new with no burn spots on the bottom of them. only thing I haven't done is invest in new plugs yet, the current plugs are from my 2007 car that has the LS2 coil conversion on it and they have about 10k miles on them. I just feel that if I get new plugs that the misfire will still occur.

compression
compression seems to be fine, the place i ordered the engine from compression tested it which is probably inaccurate, but they said it had upper 90's into the 100's psi. also even when the engine is at operating temp it starts up just fine, not as quick as my 07 with a reman engine it got a year ago though.



SOmy main question is, is why does it still read misfire even if the engine runs smooth as silk, no stuttering, no hesitation at any rpm just smoothness all around?? maybe pcm issue? or bad sensor or ground wire somewhere? or it may just really be that it needs new plugs? or something far more worse I suppose??



FYI
also I have and still own a 2007 AT for the last 5 years and have done all my own maintenance and work on it. I know what to look and listen for in a bad and good running 8.

AlexVarela

Hey Jcola I had the same issue a few months ago, my issue was the fuel pump, have you tested the compression of the fuel ? I wanted to ask you if your car turns on fine or you have to crank the engine few times ?

Jcola

sorry that was something i forgot to mention, the fuel pump in it is fairly new. I havn't checked the pressure of the system tho.

let me add that due to issues with the old fuel pump the fuel line was cut at the fuel pump under the seat. What's holding the lines together now is a piece of rubber gas tubing with some hose clamps. The clamps don't look to be as if they are so tight that its cutting off any circulation. I tested this by unhooking the main fuel line in the engine bay and the gas comes squirting out a very high pressure into a bottle.

the car also cranks just fine, maybe a 2 second delay at most that i have to hold the key

AlexVarela

when exactly you get the flashing cel ? In high or Low RPMs ? I would recommend to test the pressure of the fuel pump, it should be above 50psi I believe. Does your car get stuck in certain rpm ? I have a youtube video of my issue. Here is the link
I hope this help you to figure out the problem.

Cheers

Jcola

the car revs nicely throughout the rev range. I haven't noticed any hesitation at any rpm. the Cel blinks around 2500 rpm and when im cruising. when I lay into it it surprisingly doesn't blink as it revs up into red line.

I checked and cleaned the fuel injectors as well, they all work and actuate properly and with no leakage.

RX8Soldier

iTrader: (24)

I'm seeing a lot of "I checked "blank", and it SEEMED fine..."

You need to VERIFY if things are failing or not.
The very first post of this thread details the exact steps to take in order to assist you with finding the issue! Go through step by step and report back. Otherwise, you're giving us smoke to grab...

Jcola

Problem solved, it was indeed the spark plugs. Apparently 10k miles of the bad plugs being on LS coils and then switching them back to rx8 coils makes a weak spark which would be the reason for misfires.

ReMech

Good info

danielk015

iTrader: (1)

Solid thread. I changed out my plugs, wires and coils about 2 months ago and starting about 2 weeks, I have had rough cold starts at idle and the flashing CEL. Will recheck the plugs, wires and coils to make sure they are good to go first. Could be a dirty MAF too. Will report back.

AlexVarela

I had the same problem, and it was my fuel pump. Are you having issues with cold starts but hot starts are better ? That's what happened to me with my previous 8.

LEE911

...Thanx well enriching knowledge, but practice now...

Cypher279

So I started getting misfires yesterday, but it seems like a bigger problem than just that. My rx8 has LS2 coils and plugs that were installed when I had my engine rebuilt about 10k miles ago. I was driving down the street in 2nd and right when I hit 3k rpm the engine started stuttering and when I pulled over I saw smoke everywhere. Turns out the smoke was from my PCV hose that came off the intake and sprayed oil everywhere.

Later today I'm going to get some new plugs and see if that solves any of my problems, as I don't see my coils going bad anytime soon. But is the oil spray problem and misfire problem connected?

hufflepuff

Not sure if oil spray and misfire are related, but you might want to run an oil catch can in that PCV line.

Cypher279

Okay so after driving it for a little while longer, I can say the oil and misfire are definitely related. I replaced the plugs and now the misfires are much less frequent, but when I do get a misfire I can definitely feel a huge plume of blue smoke and loss of power for about 10 seconds while all the oil burns through.

1st gear seems to run through just fine without misfire.

2nd gear has problems. It'll rev to about 6-7k, but at WOT around 8k it starts stuttering and I get misfires and blue smoke. Also, it's apparently burning a pretty good amount of oil according to my dipstick.

3rd gear and beyond doesn't seem to have any problems, surprisingly. Maybe the misfires are some combination of engine load and acceleration? I'm very confused..

I did read somewhere that a bad corner seal can leak pressure into the eshaft housing which in turn can leak into the oil pan, which could definitely end up shooting oil into the intake through the PCV hose. Is this possible? What should I get checked out?

Any ideas?

BigCajun

iTrader: (1)

You should start with a rotary specific compression test.
You are correct about the oil blowby, it can get into your intake and foul your MAF sensor that can cause problems.

fernando7

Need help please idk if anyone has had this problem before but went to AutoZone and got check engine light checked they told me I had misfire in cylinder1 and mass air flow sensor when I drive my car it heats up and I can feel lots of heat come from engine when I drive with Windows down and when I stop at light or stop sign my rx8 turns off I've replaced my sparks plugs and wires couple months ago and when I took it to mechanic to clean the catalytic converter they stole my catalytic converter and put a some pipe I need help it's my only ride and need to fix it anybody have any idea whatit could be?

BigCajun

iTrader: (1)

I would report the cat theft to the police, that's worth about $2k new.

Test your coils, if it's been more than 30k miles, it would be a good idea to change them.
You can buy a can of MAF cleaner to clean the sensor, very simple, just be careful to not strip the screw holes.

fernando7

Can the no cat be one of the reasons why it's acting up and hearing up and turning off? I am but never gotten a reciet

BigCajun

iTrader: (1)

If you have no cat, the only thing could be pieces of the old cat blocking the exhaust.
You have misfires, usually coils, and the MAF is easily done.

Rugdog

I'm looking for a diagram of which plugs are which "cylinders". Surprised at how hard it is to find.

BigCajun

iTrader: (1)

Took me about a minute.

Rugdog

Sorry, I should have been more specific. That diagram doesn't tell you which is Cylinder #2. Unless I'm missing something.