Low RPM misfire/stumbling
 

Hi all

I've done some searching but haven't found any definitive answers to my problem. When I accelerate from a lower RPM, for example 2,000, the engine stumbles and misfires but does ultimately accelerate. I know the rotary doesn't have a low of low down torque but this feeling is new. Instead of accelerating slowly but smoothly it 'jutters' a bit, which feels like a misfire but I can't really be sure of that.

Above 4000 RPM it's great as per usual, it's the just 'running around town' in a 30mph/50kmh zone in 3rd or 4th that is the issue. Yes of course I could just keep the rev's above 4000 RPM but its not really viable.

Ignition ignition ignition I hear you say. Well that's the thing, I had my plugs replaced at my last service (7 months ago: Nov 2013) and at Christmas last year (6 months ago: Dec 2013) my coils died and I replaced them all (here and here).

Could the new coils or plugs be faulty already? I don't know the history of the leads, so that is something to try.

Suggestions welcome!

Thanks

Eccentric shaft sensor might need cleaning, mass air flow sensor might need cleaning, cat may be bad, or compression might be low. All possible if your suffering from a misfire - are you in fact getting a flashing CEL and a code for a misfire or just going off of feel?

Since you didn't mention any complaints of power loss at higher RPMs, it seems that the ignition is not likely the problem.

For what it's worth: https://www.rx8club.com/series-i-tec...t-here-222280/

No CEL code, just a stumbling feeling. All threads I found on low RPM stumbling seemed to say that higher RPMs were ok, so I'm not so sure.

I've bought some new leads & will fit them next weekend. Will also look for spark jumping at night & see how I go.

When I did the coils 6-7 months ago I had an actual misfire which would affect power in all bands (unable to drive at all) so this is more like unable to generate low down torque.

Keegs

For anyone wants to know - so I took it to the shop, they plugged it in, did their thing and cleaned the air flow sensor. All back to normal now, runs like a dream!

I replaced my cat due to a code. Replaced coils and,cleaned my maf too. Still having this,same issue with misfire or low power under 3k rpm or so. Going,to do leads and wires next but the ess sensor sounds promising too, thanks for yalls replys since this is how 21st century troubleshooting is done and so far this forum has been very helpful.

In the end my problem came back, especially when cold under load, and it was just the coils again. The ones I installed Christmas 2013 were ones from ebay that were recommended on this forum but ultimately packed it in and only lasted 6-7 months. Now I'm using the good stuff and it should be alright.

Spend the money on the BHR kit and be done with it.

Is it "that" good ($500USD)? I did some searching as I've never heard of it before and there are mixed reviews, ultimately positive though. I just watched a YouTube video of "before" and "after" the upgrade, TBH it seems the same!

See the Ignition Health section of the new owner's thread for the options of coils, and what to expect from them.

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this is just unusual
 

So I noticed that along with my low rpm misfire I also am having long,starts. Not very long, but maybe 2 seconds longer than a few months ago. The thing is, it actually starts easier when the car is warmed up..wth causes that? Low compression would make it worse as it warms up but this stays constant regardless of temp and sometimes gets better after driving. I am calling this a fouled plug. Changing plugs tomorrow to see what happens but for an idea i have changed coils, Cleaned maf, changed cat, changed the dirtiest air filter I have ever seen, checked throttle body blade or Plate or wth it's called, checked for vacuum leaks and then this starts. For a clue it started right after, and I mean within 4 miles of filling up with some cheap 93 octane, usually use techron 93, no premix. Anyway it's a 2005 6mt usdm 6 port on its 2nd motor, has 98k miles on body and about 85k on this motor. Any help appreciated. Edit: I have also looked at the ess sensor and it looks good so I reset the room fuse for the kam and fuel trims and did the 20 brake stomp and the low rpm misfire seemed to go away but the long starts regardless of temp remain.

Keegs, you did the eBay coils too and didn't last long, did you use a miltimeter to test and see which coil was dead in there or did you just replace them for good measure?

Check the battery voltage. Might be time to replace it.

oh yeah
 

So I wish more rx8 horror stories ended like this but I took my 8 out just now and did some 9k rpm pulls through 2nd and 3rd. Pulled over and turned it off. Cranked it back up perfect with no delays. Ran it at low rpms in 4th gear around 35 and the misfire is totally gone and those high rpm pulls felt way faster than this thing has ever been for me. Sounds like a love story with a great ending. I wander what fixed it? Running it so hard maybe removed some restrictive carbon from the rotor housings maybe? Kinda like how seafoam is supposed to? Idk but she runs amazing. At least for the moment lol. Only rx8 owners will truly understand that.

Yes the BHR kit is "that" good. Trust someone who has run just about every coil out there for rotary engines in 41 years of driving them. The BHR is top notch quality and performance, well worth the price, and built to last the lifetime of your RX8.