Hi everyone,

I picked up my '05 RX-8 a few weeks ago and when I started to drive it, I noticed it "bucks" when I shift gears. I saw that there are a lot of issues with the engine mounts and I took it to the dealer. They supposedly changed the L and R engine mounts and the car idled smoothly and was easier to get into gear.

But now when shifting it feels like its bucking again? is this normal in this car. It always happens when I get off the gas completely and get back on the gas. ITs driving me crazy

 

is your CEL light on? or does it blink during occurance? I don't know what detonation is like for a Rotary?

is it the Engine bucking? or does it feel like slack, then 'shockload' during clutch engagement?

you could have driveshaft play that will do this.. if there is enough play between the drive shaft and the transmission... You really should provide a consistant reproducable method, and have the mechanic take it for a drive... especially if it's under warrenty.

 

are you resting your hand on the shifter?

 

no CEL light on, most time it occurs from 3rd gear on and right after shifting or when off the gas/coasting for a couple seconds and then getting back on the accelerator. it feels almost like when letting go of the clutch too fast, but it happens even after the car is completely in gear. does the 8 usually have these driveshaft issues?

 

no way

 

yeah, my best guess is driveshaft play. Did you have bad engine mounts for a while? i've seen busted engine mounts cause transmission bearing wear on automatics if they sit cockeyed from load...

How many miles Scrapin? What rpm's & mph are you at when this is occuring? under 3k rpms? I've noticed a persistant pitched wine if rpms are to low and i'm in a higher gear, 4th gear +, below 3k rpms.... haven't done it since.


the shockload should also occur in the lower gears if it is drive shaft play. you should have it looked at, since these are carbon composite shafts..... on a bright side i believe it should just shatter to pieces instead of trying to carve you in half if it goes as it slices through frame like a boogie monster trying to get you while your laying quite.... asleep and relaxed being the big spoon or little spoon ... (I don't know you )

later!

 

Try getting on and off the gas quickly--does it buck still?

How many miles on your car? Try replacing the coils.

I replaced the coils *and* the sparkplugs recently (at 56K miles), and I can't be sure which one was responsible, but I noticed that I have a lot less hesitation getting on and off the gas. The power-back-on after shifts is smoother, with less bucking.

But I'm suggesting the coils because I read somewhere else on here that worn coils can cause hesitation.

 

I rpm have 15K on the car, and this happens at around 3000 rpm and its very noticeable around 30 mph in 3rd gear, but its there pretty much in every gear.

 

Yes it still bucks when getting on and off the gas quickly. The car has 15K on it, and its not really hesitation but a moving feeling when on and off the gas. I feel the car move back when getting of the gas and when I get back on it, the car bucks forward like 3 times until it starts to go smoothly.

 

Make sure the current flash in the PCM is up to date and all the maintenence, too. What RPM are you shifting at?

 

the dealer updated the pcm last week, and i usually shift at like 3500 rpm (+/- 500 rpm)or so when just cruising.

 

I have solid mounts and I get a little bucking from time to time when I shift at those RPMs but that is usually 1-2 and 2-3 where the gear spread is larger.

 

it feels like the car is about 30 years old. I go in my other car its very smooth, and actually all my other cars were smooth, this car is so frustrating. I will take it back to the dealer and see what happens.

 

Maybe the shocks are going?

 

I wonder if it's the rest of the PPF mounts... it's like, OK, your engine mounts are new, but what about the rest of that power plant frame.

 

Let me know also... My car has been doing this as well..

 

that is the test for bad motor mounts... as in. mazda describes that as how to test for bad motor mounts.. maybe another dealer?

beers

 

Is it possible he has a light flywheel and he is unaware on how to drive a car with one?

 

i doubt this car has a lightened flywheel, as it is bone stock in every way. Also, I had 2 240SX with lightweight flywheels and this is nothing like that. I have been driving manual cars for about 10 years and this is my first experience like this.

 

yeah I know, its just like that, but they changed both mounts and I have noticed the rough idling go away right after picking it up, but it still bucks.

 

i was thinking the same thing, and since I am still learning about all the issues about this car I can't rule this out either

 

To check that, focus on the PPF where it bolts to the rear diff.

 

Can you be more specific? What are we looking for?

 

There are 4 nuts AND one cross-bolt that hold the rear of the PPF to the differential housing.

The way that I always re-installed my PPF, and have never had any problems, was to hand thread the 4 nuts on to the point that the PPF is properly engaged on the shoulders of the diff mounting location, install the cross-bolt and torque it to spec as THAT is what properly locates the PPF to the diff, then tighten the 4 nuts to spec.

 

How to check for problems w/o rebolting everything together?