I didn't find any similar topics so please help me! I just bought my RX-8 2004 (177kw) and I would like to know where inside the engine bay can I increase revs when in idle? When in idle, the car is shaking pretty much!

 

if anything, the car would shake in IDLE. is it shaking in idle or neutral?

 

in idle!

 

It could be bad motor mounts...common issue to cause vibration at idle... increasing idle speed would just cover up the underlying issue

 

The problem aren't bad motor mounts because when I start the car in idle mode, it is not shaking at all because the engine is cold and so the revs are at 2k or 1.5K. But when the engine warms up, the revs seem to drop below 900 so the car starts to shake, then they increase for a second and fall again! So what I need (I suppose) is where to find the screw in the engine bay to adjust revs and what is the procedure. Pictures would be very helpful!

 

There is no screw. There was a thread on this topic not too long ago. As I recall, the gist of the thread was that idle speed is set by the ECU, and there's no way to change it. Several ideas came up, but they were all ones that the ECU would eventually figure out and defeat.

If the idle isn't holding at 900 rpm, sounds to me like there is something that needs to be fixed. I had a Honda that did that kind of thing, couldn't find any adjustment screws (man, I miss carburetors) and it turned out to be a control module for several hundred dollars.

Ken

 

yea the car just idles rough, it was made to idle at 900 rpms, if mazda set it up to idle smooth to much gas would be used, and the last thing this car needs is even worse gas mileage!

 

You missed my point, when motor mounts go bad you feel the rough idle (at lower RPM) much more and it seems alot worse than it is. Have you checked or replaced the mounts?

 

This car is "fly by wire" there is not a linkage connection - listen to Ken x8. Take it to the dealer under warranty. Too many things it could be including motor mounts, dirty plugs, coils -------

 

shh shh shhhh shhhh ! just shut up and listen ok ?

Your motor mount is bad, go get it fix, also update your PCM to the latest version (if you did the recall I assume you already have the latest version)

 

yes, motor mounts are the most common cause of this on a stock car, by far.

 

Last friday I went to install Unichip to flatten up my engine power curve. When the car was on dyno, at 4500 rpm the power rapidly fell from 80KW to 57KW and at 6500 rpm there was very loud noise in the engine bay. The noise can be heard only when on dyno, not when driving. I immediately went to authorised Mazda dealer and first they noticed that the car is shaking when in neutral. They waited when the car got cold and did a compression test. In the first chamber it was 36% lower than normal. The result of all this was that I need a new engine! The warranty expired a month ago, but I was still in the warranty mile range so Mazda Europe authorised a new engine and 100% cover of costs. The engine is coming on tuesday!

 

And the motor mounts were fine and I also have the latest PCM (the one that doesn't allow you to rev the engine when cold)!

 

is that one of those e-bay $20 for 20 hp chips?

 

No, I went to install original Dastek Unichip from an authorised dealer in my country. The price is around 820 US$. I just wanted to flatten the power and torgue curve, as I said. Also I wanted to optimise the gas/air mixture the engine receives in accordance to sea level of my town and the quality of gas and also to have two consumption maps, one for town driving, one for faster driving. Mazda optimizes gas/air mixture for engines delivered to the whole world to cut expenses of tuning the car individually for each country. The gains in hp are small and depend on sea level where you live, on the quallity of gas and on your engine's condition. Dastek HQ in Africa sent me dyno results of RX-8 tuned for area that is 1200 meters above sea level and the gains were 9hp.

 

Glad to hear you figured out the problem! Hope all goes well with the new engine. I would make sure it is broken in properly before putting on the Unichip just in case you have any issues.

 

hello dvidic, have you been able to fix the shaking of your rx8 at idle rpm i.e. below 900? i read your problem and i am facing an exactly the same issue, i have the the engine mounts and they are absolutely fine... can you suggest a remedy now or you are still stuck with it?

 

look at the post dates.

bad idle.

plugs
wires
coils.

mounts.

beers

 

vacuum leak too, I've seen many bellows between the intake and throttle body not fully tightened, you need to crank that mother down, also found a broken MAF sensor O-ring once too