low idle problem...at wits end
 

I have an 04 rx8 that idles around now 800 rpm maybe a little more. It was idle at 740 and above. I have replaced coils, plugs, wires and cleaned the maf sensor. Fresh oil and air filter. And ran a fuel injector cleaner and today I did an engine flush and cleaned the throttle body but it still idles anywhere from 780-840 rpm. It only has a problem at idle. Does anyone have any clue on what is wrong?

Maybe a clogged cat converter? You could get a compression check to make sure the motor is good. It sounds like you have changed the usual suspects of this problem.

The compression check is my next step. I want to straighten out the idle problem before installing aftermarket parts on it. But if it comes to the cat then i will change the whole exhaust.

I called and asked the mazda dealership to see if flashes were done and all they told me was the the 4206f recall had been completed

I wonder if your AC or Alternator could be messed up and putting a drag on the engine. If the AC is turned off, but is still engaged due to some failure in the AC clutch, it could put a load on the engine and the ECU wouldn't know to increase the RPM to compensate for the additional load. If the bearings are going out on the Alternator, that could also put a load on the engine. You could take the belt off and make sure all the pulleys spin with little effort. Also you might want to inspect your vacuum lines and take a vacuum gauge to them to see if there are any clogs and/or leaks. It doesn't hurt to disconnect the battery, wait a little bit, reconnect it, and see if the problem persists. Sometimes the ECU just has to be reset. You might get a code scanner and make sure your sensors are giving the ECU realistic values. Your MAF sensor and IAT sensor might be clean, but if there broke or giving false data, who knows how the ECU will respond.

I have an obd2 scanner, do you know what the maf reading should be?

Sorry, I don't.

Thanks for the help anyways. If anyone knows please help me out

If you find out what the MAF is supposed to be, could you post it on here? I would be interested to compare mine against the ideal number.

That's the normal range for a Manual :dunno:

750rpm is pretty normal...

EDIT Brettus beat me to it!

I was looking at another thread (https://www.rx8club.com/series-i-trouble-shooting-95/p0335-eccentric-shaft-position-sensor-circuit-problem-car-will-not-idle-194505/) and some guys were saying the Eccentric Shaft Position Sensor has a tendency to pick up metal junk off the road (since it's magnetic) and throw off your computer. It sounds like it's an easy enough thing to take out, clean, and put back.

Well I just looked under my car after driving and I had a glowing cat at the O2 sensor so time for a new cat. Also it wasn't just the rpm fluctuation but I also have some bad vibrations and my passenger side floorboard gets pretty hot. So now my next step is to buy a high flow cat and then see how my 8 runs after that.

Also does any body have recommendations on best exhaust. I have been through the forums but just can't decide. I was thining about buying the kit from sr motorsports, it comes with pulleys, high flow cat, cat back exhaust and cold air intake. Is anybody familiar with sr motorsports?

Borla FTW, if your going to buy an exhaust they are developing specialized mufflers for the rotary engine.

I was thinking about the turboxs exhaust but not sure if I should go with the cat-less midpipe or a high flow cat

Would a bad cat cause rough idle?

I like the borla exhaust as well, how many miles do you have on your 04 8?

no , not unless it was totally blocked . In which case it would hardly run at all ...

vibration could be from a faulty engine mount - known issue

To not post a new thread...

Mines been idling a TAD rough but since you guys said 750-850 is normal then i guess i'm just being picky, it never drops below 700ish or bounces higher than 900 so i guess i was just expecting it to hold at a steady RPM. I'll still check all the usual issues and for leaks.

Also to note on the cat issue...i having d a rattling noise between 2-3k rpms mainly when im coming to a stop or i'm in neutral or have the clutch in and rev up to 3k. This combined with a p0420/cel and a foul smell after shutdown and hint of gas thru the air vents with the AC on pretty much tells me my cat is shot and i'm assuming that's the noise i'm hearing? So i need recommendations. Go with a catless midpipe or get a high flow one? If i go with a midpipe won't i still be getting a CEL since there will be no cat at all?

Update, took it to dealership. They ran a compression check they said compression is fair and I have a bad motor mount and a fan that isn't spinning. They spark plug holes were mildy stripped so plugs were in a little crooked, they fixed the spark plugs. Gotta go back in 2 weeks and get another compression check and if it worse they are going to try and her mazes to cover the cost of an engine replacement. If mazda wont cover it then it's time to scrape up $5000 to pay for the new engine and labor for the swap

Sorry for the typos, I am doing this on my phone I meant to say have mazda cover the cost.

If mazda will not cover the cost does anybody know of a company that sells engines that aren't quite stock?

Mazmart, https://www.rx8club.com/mazmart-88/remanufactured-rotary-engines-104255/ the last post in the thread was from 2/27 and listed the price at about $4600 for a basic engine if you give them your core and heres the post about it. I think they can also do more to the engine at a higher price.

I have also been looking for someone or a shop that knows what they are doing in the hamptons roads area of Virginia