Revoluzione

I bought an 04 RX8 (automatic) a couple of weeks ago and have noticed that at speeds of between 35 and 45 mph in 4th gear the car seems to jerk. Its not a violent jerking, but it feels as if the engine is choking. Put it this way, it definitely doesn't feel right. I've never owned a rotary before, so I don't know if this is normal. Its not right? Does anyone have any ideas? Also, sometimes when I change from manual mode to auto while driving, the gears get stuck in third and wont go to 4th. I have to put it back into manual and then change to 4th. After that if I put it back into auto, its usually fine. Any thoughts?

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zoom44

i dont have the auto but ive driven a freind's a few times. isnt 35 a little slow for 4th? the otehr could just be "user error" not being used to it yet.

my10ae

In 4th gear at 35 - 45mph is way too high of a gear to be in. There is no power in that gear at those speeds. What's the RPM range at.. 2300? Try down shifting 2 more gears to 2nd and you'll see a significant gain in power. Seems like wrong gear, for wrong speed issue... :D

zoom44

thanks^

jerryf

This is something that generally happens when the engine is cold (in my car) and fades as it warms up. I believe (and experts can confirm or deny) that it has to do with the 2nd fuel injector coming on. I usually limit the car to 3rd gear untill it's completely warmed up.

As to the wrong gear for the wrong speed, it's an AUTOMATIC transmission. The engine management system selects the appropriate gear based on several factors. 4th gear at 40mph does indeed keep RPM's down, maximizing economy. To roll around in 2nd gear to keep RPM's up on your way to the grocery store is pointless, and will cause your ice cream to melt when you have to stop for gas on the way home. :p

EyeBall Fixer...(o)(x)

Hey Revoluzione!
Welcome to the Forum.
I have an A/T and when cruisin' around town (35 -40 mph) the 8 will pop into 4th gear.
As for the "jerkiness" (particularly on colder days), the 8 will not be very smooth running...
Also, if your not at full operating temperature, it will (at times) get stuck in 3rd gear until she warms up.
Finally, don't fudge on gas! Use 91 octane or higher.
Al

derwankel

Nah ... I cruise around in 4th all the time at 35-45 ... it's fine. Now if you try and accellerate hard from there it's not gonna snap you back in your seat. In that case, sure, I'll drop it down to 3rd or 2nd . But driving around in 4th at that speed is not a problem. It sounds like the owner needs to take it back in for some adjustments. As a side note, if you leave it in full automatic it will be in 4th by 30 mph ... depending of course on the fact you are not trying to accellerate but rather cruise.

With respect to :

This sometimes happens, and is a result of the logic in the tranny. Not the most elegant situation. When that has happened to me, I either take my foot off the accellerator to get it to upshift, or I do as you have. The transmission learns your driving style and shifts based on programmed logic. If your logic (which it is learning) is to be in third when you hand over the shifting to the computer, then it assumes you want third.

It may be somewhat exaggerated however, as I do think (in my remote diag mode here) that you may have an issue if it is indeed "jerking", albeit mildly. Again, if it is noticable, take the MAZDA tech for a ride and show 'em.

my10ae

Ummm did you forget you can not only drive your 8 in fully auto mode, but also in auto-manual mode? You can select the gear you want to be in when in manual mode and keep at whatever RPM you desire. Fully auto mode with this car is just plain slow. You need to bring up the rev's to have any power in this car (and any rotary engine acutally). Tooling around town in 2nd gear(and higher rpm's) is better for the car then lugging it in 4th at 35-45mph..

To each their own....

therm8

Ideally this is true, however this transmission computer coupled with this engine doesn't always work out. It'll shift to 4th at very low rpm, left to its own devices. Then it'll act just like a manual car and bog down significantly. Gas mileage is based on fuel delivery. Fuel delivery is based on throttle position for the most part in closed loop. I don't shift to 4th until I can cruise above 40mph and I get 16-18 mpg city. If I'm stuck driving at 25mph I'll keep it in 2nd.

Vertigo-1

I have this exact same problem whether it be in tiptronic or full auto mode...3rd or 4th at 35 mph or less makes the car feel like it's going to die...exactly the same feeling as a manual that's about to stall. Point is, it's an automatic, and just about every automatic in the world follows the same logic, shift to overdrive ASAP, without feeling like it wants to die.

Normally I don't care because I use tiptronic just about all the time and will generally keep it in 2nd gear, but then you run into cars that speed up and slow down between 35-37 mph, and at 37 mph in 2nd, you start heading towards that magical 3750 RPM 2nd fuel injector point. So I go into 3rd for like all of 5 seconds before dipping back down to 35 mph or less again...and the car starts bucking. Go back to 2nd, rinse and repeat. Extremely annoying, and not pleasant on the gears.

What really worries me though is that this could be pointing to a problem with the tranny...there's been some members that have said their autos don't have the same problem. And yet this is likely something the dealerships are going to just shrug off as "oh, it's in too high of a gear".

jerryf

The root post here didn't mention anything about an acceleration issue. Besides, my AT accelerates to the posted speed limit just fine, regardless of shifting mode :p

I know a couple of AT owners who only use MANUAL mode. It just seems silly to me. More often than not, the car knows what gear to be in better than the operator. There was a poster a while back complaining that his car wouldn't accelerate from 25mph, while he was in 3rd gear in MANUAL mode. If he'd been in AUTOMATIC mode, the car would've downshifted to 1st and accelerated nicely. The car had nothing to do with the acceleration problem, it was the operator!

Unless you drive around in the heart of the powerband, AUTOMATIC mode will yield faster acceleration than MANUAL mode, because the car can select the proper gear faster than you can. If you do drive around in the heart of the powerband, you'll be able to pass anything on the road...except a gas station.

Back to the root post. This happens on my car only when the engine is cold, if it happens once the car's fully warmed up, I'd pay a visit to the dealer.

therm8

in auto mode, the car shifts at 7000rpm, in manual mode you can go to about 7700rpm and will put you higher in the power band in the next gear. I can select 2nd gear from 4th (as long as i'm going 71mph or less) just as fast or faster than the computer. I drive in manual exclusively and have no mpg issues.

my10ae

AMEN my brutha!!! :D

Vertigo-1

By itself the RX-8 simply follows the same typical automatic logic of every other automatic out there...shift into overdrive ASAP. Cruising at 40-50, stomping on the gas tends to just bring you out of overdrive and into 4th. Stomp on it more and maybe you'll get it to go into 3rd. It will just about never go into 2nd short of slamming the car into WOT, which makes the driving experience rather unpredictable and jerky.

Most autos also seem to have a problem where they get "stuck" in the current gear if you get on the gas hard, and yet when you take your foot off, it won't upshift...it'll just stay in the current gear for a bit longer.

The car by itself also has no clue how to set itself up properly with a downshift before a turn so that you can power through the turn.

jerryf

Except the car makes max power @7200rpm, so...


All my previous remarks were for everyday driving conditions. Track, or autox, or "spirited" driving is entirely different. In those cases manual control makes more sense, including DSC and TC. But using MANUAL mode and disabling DSC on the way to the club is more likely to make your girlfriend carsick than anything else.

therm8

doesn't matter, still makes more power from 7200-7700 than at 4 or 5something. average power is what matters.

Revoluzione

Thanks for the help guys. I'll go manual for a while and see how that helps.

JeRKy 8 Owner

I tried what you suggested - staying in 2nd till 40mph and thenonly going to 4th afterwards (basically staying out of 3rd) and my mpg last week went down - barely even made 15mpg. I think Ill stick to the waythe car regularly drives b/c your driving method dropped me almost 2 mpg.

310Guy

I will agree with that. I use the manual mode about 90% of the time. I know for a fact that I'm better able to "drive" the car, especially through a turn, controlling what gear I'd like to be in than if the car does it for me. Indeed, you have to keep the auto 8 in the sweet spot for her to move...

Vertigo-1

I can't help but drive in manual mode...it's way funner, and I think it's much faster in bringing on the power as needed, as by itself the car tends to bog down between downshifting between overdrive, 4th, and 3rd at typical city speeds. I never shift into 4th when in the city...usually hovering between the ideal RPMs in 3rd for a rev matched downshift into 2nd as needed to power through turns or pass cars. The AT certainly isn't slow if you drive it properly in tiptronic mode...granted that it defeats the purpose of automatic, but oh well.

Today I took the car to redline in first and almost to redline in 2nd going WOT, and in both cases the engine continued to rev upward immediately after shifting. Rather funky...and definitely makes you want to shift well before fuel cut off, or else it could accidentally over rev right into the fuel cut off point by itself. I guess that's part of the problem with how tiptronic works, and how you have to keep your foot on the gas when you're upshifting.

markd

I agree with Jerry--I don't think this is an issue. Even in manumatic mode, the car won't let you shift into too high of a gear. If you're going 10mph, for instance, you will only be able to shift into 1st or 2nd gear. 3rd and 4th gear are restricted at that point.

As for the jerking issue, I actually started a thread on this back in December: Car jarring while in motion. I have had the same problem, and continue to have it, although I have not yet reported it to the dealer. If anyone is able to resolve this issue, please let me know!

Diabolical RX8

35-45 mph in 4th gear is no problem with an AT RX8. I myself have one and I cruise in 4th gear at sometimes even lower speeds. (not in manual shift) So that answers peoples opinions on to high of a gear for a low speed.

Now for the jerk you feel. I have the same thing when I press on the gas alittle bit to hard in 4th gear. So I usually downshift into 3rd and possibly 2nd if I need to.

I have some pictures i can show yall really quick.

Almost 3k RPMS at 69mph


Almost at 5k RPMS at 119mph


See the ratio of the rpms?

50 MPH difference in 2k rpm's. Not what you would expect is it.

JeRKy 8 Owner

In general driving I usually dont keep it in tiptronic mode for two reasons.

For somereason if youre shifting manually andyoure in 2nd 3rd or 4th going exactly 30mph it wont let you go into to 1st - you haveto be at 29mph or below. BUT whenyoure not in tiptronic mode and youre going exactly 30 in 2nd 3rd or 4th and you stomp onthe gas - it drops you all the way into 1st gear.

Also lets say you were only going 28 - 29 mph. The timeit takes for you to down shift the stick or hit the down paddle from 4th to 1st or 3rd to 1st takes longer to shift than whenthe computer shifts for you when you stomp the pedal. So whatI usually do is go into tiptronic mode directlyafter the computer drops it down to 1st gear.

Anotherthing youll notice is if youre cruising in 4th gear at around 40+ mph and youre driving in tiptronic mode andyou want to go into 2nd - theres usually a couple second delays in going down to 2nd gear from 4th at those speeds when using tiptronic mode. This is another situation where youre better off NOT being in tiptronic mode b/c the car will downshift faster by itself in reponse to you stomping on the pedal.

Its pretty disappointing to say the least.

markd

Here is a link to a post with actual numbers on the gear ratios, for anyone who's interested:
http://www.rx8club.com/showpost.php?...8&postcount=17