Hi there, I was going back reading about misfires, and just for clarification, it seems people think glowing cats cause misfires. I always believed the misfire
(unburned fuel) causes the cat to glow. Dealer wanted to charge me $1400 for a cat and never talked about why it went bad. I get the impression some people think replacing a glowing cat will fix the problem. The root cause is faulty ignition parts dumping fuel in the exhaust, which is burning in the cat, right?

Correct, misfires mean unburnt fuel and unconsumed air that is being dumped into the exhaust, which is ignited there and the end result is a blowtorch on the cat to some degree (intermittant to severe). Misfires cause clogged cats.


However, a clogged cat can ALSO cause a misfire, which is where some of the confusion shows up. :)

could it be my injectors? ive tried looking for some way of cleaning them, does any one have a diy for that?

Lol thanks for answering that one, I haven't been able to keep up on this thread as much as I hoped. I almost should note that in the OP (Can't assume everyone would just know some things which is perfectly fine)

See this thread, specifically post #4. Should point you in the right direction :)

https://www.rx8club.com/tech-garage-...cleaner-68828/

Tylerk,
Look up P2096 on the forum. I believe it has something to do with the MAF sensor. Even if you cleaned it, you could need a new one.

This is great info. I posted a topic asking about this about two days ago.
I was having issues with my car turning off when I reduced the speed.
Took it to the dealer and they told me rotary 1 had 2,261 missfires and rotary two had 46. I had the P0301 code.
I'm in the process of changing out the spark plugs and coils.

does anyone know a good way to check fuel pressure? i am thinking its either my maf or fuel pump. what do you guys think?
Thank you all for the help

fuel pressure gauge

thanks for the advice, i was looking into putting one in. do you have a diy for that? ive never installed a gauge before. i can handle the electrical stuff (wiring), i work at best buy in the install bay, im just not sure what all i will need and where to get the pressure reading from.

Thank you, Tyler

2004 Rx8, 112k on chassis, 65k on engine.

It seems out of nowhere, my engine is now missing while idling hot.

Throttle very responsive, power very smooth all the way to redline, just got 21mpgs on a trip to Gulfport.

Oddly, the only way it will idle flawlessly is with the A/C on.

Already checked for vacuum leaks.

I took a couple of video clips, Thoughts?

^ I never had time to get through the entire video, but short fuel trims and everything seems like its fine (confirmation from someone else here would be good), but have you actually gotten any misfire codes up?

Even with the BHR kit and newer plugs, hooking up an inductive timing light on each would be a good idea while at idle and revving slowly up to top to see if there are any misses or skips. You also say that when the AC is on the car idles fine, now I'm not sure what effect having the AC on during idle would have on the throttle body, but I assume that it opens it up a bit as it puts strain on the engine. I say this because maybe there is a bypass issue for when at idle? Seems extremely unlikely, though, if not impossible.

I will take a better look at the video tonight and see if I can come up with anything, maybe in the meantime someone else can pipe in who knows whats going on better.

No codes. Idle RPM is set 875.

I took another look at the video, and I'm not sure that sounds like a misfire problem. Initially I would have said check over the entire ignition with a timing light, which I still recommend, but after you stating how perfectly the car is running otherwise that makes me stray away from most typical issues.

I'm almost aiming towards the air intake bypass for idle, but again it should be choking more than that. Is this the only problem you are experiencing? It's hard to hear when it misses/skips a bit, but I know mine has sounded like that for some time and I'm now having to replace an engine (most likely)

Without a code up or any other issues like rpm drop, hot starts, power loss or throttle responsiveness, I would say it probably isn't something to be too concerned about. You're compression is below Mazda spec, and even when it is right below that can cause small, minimal and sometimes quite unnoticeable issues

I ran her down to empty and added 5gallons of gas with a bottle of techron a day before posting, light is about to come back on and she seems to be idling better... Who knows it could be the weather, it's been warming up. Mornings are in the low 60/50's and after noon are near 90,might be having trouble adjusting..

As soon as the "hot starts" become a issue I will be replacing the engine, and I honestly can't wait to see how she acts with a proper engine.

Temperature will affect idle and performance. Air temp and density will cause noticeable effects so yeah I wouldn't worry to much. Just keep an eye out for compression issues and just get a test done every year or so.

Must be nice to have a running car! Lol

I hit the coils with a timing light last night, all are firing. My friend is now also baffled by the issue. :lol:

Gonna be servicing the the battery terminals and some ground points today, saw a little bit of corrosion while we were under the hood.

Lol I'm almost baffled! If the timing light test went fine then only other thing I could think of (off the top of my head) would be injector issues or intake bypass... but you'd think you'd see more problems from those things...

Update:
 

After burning thru the 5 gallons of gas and having a slightly better idle, I went ahead and added a bigger bottle of techron (treats 20gal) and added 8 gallons of fuel. Just finished burning thru that, idle has gotten much better, going to fill up tomorrow back on premix.
Still not idling "perfect" but man it's so much better than before, maybe it's just carbon build up... I drive her like a bat out of hell in the mornings on my way to work, but when I get off, it's stop-n-go traffic all the way home. To give you and idea... I can make it to work in 17mins (hauling ass,4am) but it takes at least 45mins to get back home.

In a week or 2 I'll be doing a good bit of work on the car (coolant/radiator/fans/oil) and I'll go ahead and seafoam and see what that does. If no improvement I'll just blame the low compression. :lol:

Thanks for the help. :)

-Shawn

^ Glad to hear you're seeing some impovements! Lol and yes even slightly lower than Mazda specs can cause issues

Hello I am new to the club I am getting a misfire I think but any was the rx8 brakes up the higher the rpm's if I can keep it between 2k and 6k rpm it pulls hard and runs for the most part pretty good but pulling hills or flooring it past 1/4 throttle it brakes up backfiring if I could get some help it would be gratefully appreciated

Do you have any CEL's up? (Engine light). Also, I just need you to clarify exactly what you are saying here: Are you saying that when you try to put the throttle past 1/4 way, it bogs and has no power? If so, is this throughout the entire RPM range?

I would guess bad/faulty/loose secondary injector.

My s4 rx7 had a issue like that, would pull fine all the way to redline provided you stayed under half throttle. If you floored it above 4k, it would miss and backfire. Turned out one of the secondary injectors was unplugged.

Having misfires, only when engine is coldish. as in when I first fire it up until about 20+ mins of highway driving. Misfires over about 5k. And no I don't start the engine and rev the piss out of it when I first start it, I let it warm up, this a new issue. AP reader says misfire cylinder 2. It started happening after I put the factory cat back on. I have bhr coils, newer plugs, new wires an AEM cai which is clean as a whistle. Cleaned knock sensor. O2 sensor is fine as far as I can tell. Car just started to do this after removing BHR mid pipe and putting factory cat on. Kicker is factory cat is brand new. Maybe 500 Km's on it.. The day before i put the cat back on i was actually at a dealer who ran a misfire count that checked out amazing. anyway dealer is a dick now and is saying I should remove the bhr coils back to factory ones.. Which we all know are junk. So that's not happening. Not sure if anyone has ever experienced the same symptoms when going back to the factory cat. Any pointers or info would be great. Thanks in advance all!