risky business

hi guys, i own a 2004 rx8 with almost 70k miles on it. ive had it for almost 2 months now and i try to keep it in the best condition possible. i do everything myself and when i first bought the car i noticed it was rough just above idle. at about 1100 rpms. i figured this was due to the spark plugs being changed and possibly also because it didnt have to most recent flash from mazda. well i have had the most recent flash AND the plugs changed and it is still rough at 1100 rpms no matter if the car is cold or warm. ive heard that the older ones have a rougher idle then the new ones but i dont think they are supposed to be as vibrant as mine. Im thinking replacing the wires could fix this problem but i wanted all of your opinions before i spent money i really dont have.


- adam

nycgps

iTrader: (1)

when u say "roughness" what exactly do u mean

is it just idle? or when u're trying to move ?

AT or MT ?

but it does sound like ur motor mount. do u know if the previous owner ever replaced it ?

LuvMyRX8

Check and make sure you don't have a cracked motor mount. If you do a search you should be able to find pictures of what a cracked and good motor mount look like.

04RX8man

yeah sounds like a motor mount to me also..I think there is a TSB for that

risky business

I have a manual tranny... i happen to be on a test drive with a mazda mechanic recently and i mentioned it to him and how i thought it might be a motor mount but he said that it wasnt because we would be able to feel it big time (as we were cruising at 45)... ill have to inspect them myself tho, thanks for all the opinions.

fastlaneracing

My car is also abit rough at low rpms when its cold.

I think there is nothing to do about it, had simillary problems with my CTR.

al high rpm cars without low end torq has a bit "rough" idle special when they are tuned.

RK

iTrader: (1)

I thought changing tranny fluid can help with a rough idle, no? Hmmm... Time to go into n00b search mode...

neXib

I can't say I agree.

When I started my car and opened the hood, my "piston friends" couldn't believe how quiet and calm the engine was. There's nothing rough about it, until you step on the gas

swoope

iTrader: (5)

not correct.

beers

swoope

iTrader: (5)

no is correct.

beers

nycgps

iTrader: (1)

nope, if u know Rotary's history, u will know thats not true.

Your Mazda mechanic is wrong. u will feel the broken motor mount only when its idle, or hesitation when u're @ 3rd gear under 3K rpm then u try to speed up.

nope.

fastlaneracing

Okey so something is wrong with my car?

It has been that way since I bought it.

Driving in like 15km/h in traffic jams is a pain in the ***, it was almost excactly the same condition with my previous CTR so I just imagine all high rpm cars had that problem.

Well im taking my car to a Rotary tuner next week for some tuning, I'll ask him if something is wrong.

neXib

If you want your problem solved, explain properly what the roughness feels/smells/looks like. And exactly when and when it doens't happen.

Renesis07

iTrader: (1)

Mine does the same, done it for 3years now. Oh well. Btw, its 100X worse with the fan on, mine doesnt idle as rough with everything off.

simplyphp

omg did you ever get your problem solved? HOW DID YOU FIX IT?

risky business

ok. the roughness has no smell. it seems to vibrate at 1100. it almost feels like when u rev a manual car to low and it is about to bog out. but also the car has a roughness to it when cruising and using the gas or stepping off the gas. it feels more "jolty" then it should. for ex if you are cruising at 45 in say 5th gear and you do not have your foot on the gas, then you put on the gas it isn't smooth. it kind of jolts forward for the first second. i thought this might be due to spark plugs but since i changed them the problem hasn't been affected

Old Rotor

Please give us all the info on your car, to help us help you...

rXter

One comment on the motor mounts. I just found out that my front mount was broken. Symptom was a very high frequency vibration (not a clunking or grinding - not real obvious, but there) and a courseness to the sound of the engine. No change in attitude of the manual shift rod, although the vibration was passed through the shift rod, as well as the pedals, esp the clutch. Most pronounced at higher RPM, esp with quickly rising RPM.

Leesha

I sort of had a vibration on my shifter when my car was new however I haven't noticed the problem in quite some time. They couldn't figure it out at the dealers either so I didn't want to push for a new engine as my car was new. Some breaking in is all it took I guess...

Btw motor mounts were checked. I know of someone else that had the same issues got a new engine and his car hasn't had any probs since...

rXter

Hey risky did you get your rough idle problem solved?

SayNoToPistons

iTrader: (8)

I would also like to know.

My RX8 GT 6spd has SIMILAR symptoms with ~47k miles. It has a bit of idling vibration ~ 1,000 RPM but goes away when I tap the gas a bit at a stop, but comes back when it's idling again. The shifts from 1-2 and some times 2-3 then to be a bit jerky. It also tends to jerk at low RPMs in 1st and 2nd gear when I am going slow in city driving, almost as if it is bogging. Power delivery is smooth and performs well when I don't drive it like a grandma.

Coils were replaced ~ 15,000 miles ago along with spark plugs and wires. No issue with the engine idling itself, just the vibration.

SARRAS

Based on these comments.... three things. At 45 miles per hour in fifth - if you want anything more than leisurely acceleration, change down to third. You're not driving a V8 - rapid speed changes demand rapid rev rises in this car so changing down is the way to do it. Secondly / thirdly - clean the MAF and the throttle body - at your mileage if neither of these have been cleaned they're most likely filthy and either or both of them can cause these symptoms if dirt and gunk has accumulated.

rXter

I'd also consider the coils. I had a misfire at about 800 (normal idle speed for my car) and a little hesitation when running up through the rev range, with a sense of lower grunt below 5K. Changed the coils and it runs great again. There is a DIY here for coil change. 2 hours and about $100.

stevenmu

I've only had mine a short while so my observations may not be correct, hopefully someone more knowledgeable can correct me if I'm wrong, but in my experience:

• When warming up the engine idles around 1100-1200rpm, it sounds a little rougher than when warm but shouldn't cause vibrations
• When warmed up, it idles about 700-800rpm, because of the slow speed it will vibrate through the car a little.
• When warm, revving the engine to 1100rpm it should be smooth as extra smooth butter which has been melted and put through a smotthening machine.
• When driving, having the engine at low revs ( <2k ) can be a bit jumpy.
• This is more noticeable in lower gears.
• This is especially noticeable when the engine is cold. When it's cold the engine runs very rich, i.e. lots of extra fuel, at lower revs the engine also has trouble sucking in lots of air. Lots of fuel and very little air makes it difficult for the engine to precisely control detonation causing bogging. (bogging isn't good for any engine, but I've heard it's very very bad for rotaries and to be avoided)

Some tips:

• I tend to try and avoid driving much lower than 2000rpm, particularly when cold. When it's well warmed up I'd go as low as maybe 1500 or 1600 as long as it doesn't feel like it will bog.
• In very slow moving traffic you can try "bouncing off" the clutch, i.e. start tp take off as normal but once the car begins to move just put the clutch back in instead of letting it out fully and coast.
• Leave lots and lots of room to the car in front, you'll find that often when it stops or slows to the point where you would have trouble, it will actually have started moving again by the time you catch up.
• Note that just because the temperature gauge has reached it's normal position, that doesn't mean the engine is fully warmed up, you'll find it will run smoother at low speeds if you've had a good long run beforehand.

Hope some of that helps.

RXTim

Just wondering if anybody found a solution to this problem. My '04 has the same vibration and I can't seem to find another thread about this specific problem.
To explain more clearly, if I rev the car in N and let off, the idle drops down quickly to a point just about 1200 rpm, then slowly moves down to idle, which I think is normal, but from 1200 down to 1000 rpm there is a strong vibration that can be felt throughout the car. The vibration is also there on take off from a stop, unless I give it more gas (too much), and also when coming to a stop with the clutch depressed.
It doesn't feel to me like an engine mount problem, but more of an engine bog or hesitation!
I've replaced my plugs, wires and coils(BHR), but although that helped with other problems, the vibration still exists. I have also cleaned the throttle body as well as I could without removing it.
Do you think it would be worth the trouble of removing it for a complete cleaning. Could this be all that's wrong?