Just got an 04 RX8 with 10,000 miles. 6MT with just about every option.

I feel some sort of slight loping surge or rump in the car at idle. Under my ***/in the seat. However, RPMs don't fluctuate. Anyone felt this, is this a problem, should I be worried, etc.?

This is my first rotary. As far as data, all I know is that its first tank of gas in my possession netted 17.7 mpg on premium, and it seems to run fine. Could use a Garrett T3, but, well, you know how that goes...

 

I like the way you put it, a slight loping surge or rump in the car at idle. Nobody has complained that the 8 idles particularly smoothly. Some have argued that given its design, it's a wonder it idles at all. So some roughness is to be expected.
Be advised, though, some owners have experienced a motor mount failure which seems to contribute to feeling of a rough idle. You could have your service dealer take a look next time you take the car in.

 

You could try cleaning your MAF sensor to smooth out the idle. It maybe dirty with oil getting sucked in.

 

the thread why does the renesis "lope" at idle might be helpful to read. but i havent in a whjile myself so dont remember if there was a conclusion in that thread or not. i have my own theory

 

OK paid more attention yesterday.

Idle is smooth at 1000 rpm and above, but it does not stay there for long (only when getting up to temp). Then, it dips to about 850 rpm and struggles. I wish there was a way to simply raise the idle speed. Nice to finally have a car with a warranty, but I will not have a chance to have it seen for 1.5 wks. It might be a dirty MAF sensor. But 850 rpm is does seem awfully low for this tiny-displacement engine...

Edit: thank you zoom44 for that link to the "loping" thread. Described all of the car's symptoms. Guess they just set the idle too low to scrape 0.1 more mpg or a few less ppm NOx out of the car. Hopefully I'll get that reflash that corrects this, which is what the Mazda tech lady suggested to me what was gonna happen.

Or, I guess I'll just live with it, believe me I've dealt with FAR more radical idles b/f.... like my dad's 246 @ 0.050 duration cam trying to suck air through unported heads...

 

Normal rpm at idle with the engine warmed up is between 800 and 850, NOT more!

Normally at this rpm the idle should be smooth, only the shifter is vibrating a bit.

If your idle is not of this kind have the dealer check MAF sensor and spark plugs!

 

yes , check the plugs. My idle was lumpy at 40,000k odo reading. The plugs were replaced and my idle is now very smooth.

 

My car ('05 shinka, built 11/04) tends to have the typical 13B idle, smooth throuth the wheel and pedals and seat, but the shifter does vibrate a li'l bit.

One thing I've noticed, this engine doesn't like being babied. After an afternoon of puttering in traffic, the idle gets a bit rough -- till I take it to the freeway and redline a few gears.. then she's happy again.

Plugs must foul quickly, I guess... reminds me of some old italian cars. :D

 

Had the same problem, got my car back today and they replaced the plugs. They claim the plugs cost 146.00 a set. They are smoking crack if they think people will pay that kind og money. By the way I am just under 19000 and have had the plugs replaced twice now.

 

Actually that is what it costs from the dealer for plugs, and the cheapest you can get them online is around $100. These plugs are unique and only made for rotaries, they get what they want for them.

 

do you know how much Mazda in Cyprus sell the spark plugs????? $250 the set ...yes that's right!!!

 

OK update:

Took it to the dealer today... only to have them do nothing, and the car run the same! According to the master tech @ Tom Bush, the rough idle pulse was "normal for rotaries" and the bad fuel mileage means I "must be driving it too hard."

No trouble codes were thrown. All recalls and ECU reflashes were up to date. The only problem found was a loose ground wire from the battery, which caused the CEL to come on for a few hours after an autocross last weekend (makes sense - g-forces caused the battery to move a little and the wire to stretch).

More data points: I have gotten 17.7, 18.9, 16.4, and 16.5 mpg, all on premium, all with roughly 50/50 city/highway. Awesome for a 6-speed, 1.3L, 2800-lb car

Soon I'll pull the MAF, air filter, and plugs myself... as Tom Bush wouldn't do it because "no codes were thrown, and they would tell you what to check".

If cleaning those items doesn't change the situation, I guess I'll live with it. If everyone said this is normal, I would accept it and move on, but that's not what y'all have said...

 

I was gonna say for you to take it out and run the **** out of it but i'm sure you did with autocrossing. I thought it could be carbon build up but what do i know...lol.

Brian

 

I ThOUght i was the only one with the prob...thank god for this site...I had the dealer check everything and my MAF was replaced due to an intake warranty episode NE ways it seems to be normal and I tested one at the dealer it did the same thing....also they backfire when you rev if the engine is cold

 

From the info you have given us, I would agree with the dealership. The rotary is going to lope at idle, it is just the way it is. You gas mileage is right on par with everyone else, just have to live with it. As long as the car is spinning up and running good flooring it down the road, I would say it is just fine.