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Thanks Will. I suspect that it has something to do with the electronic brain managing the transmmission. In Full Auto, it's upshifting fine, but it's not downshifting when it should (upon braking or coasting to a lower speed) to prevent the RPMs from dropping to the point that it begins to lug and stumble when accelerating lightly. Of course, when really mashing the throttle to accelerate it kicks down, but there's a little hestitation there as well. I'll get the diagnostics done at my local shop and report back on findings. Thanks again for testing and reporting. :)
Okay, I took mine out for a spin in full auto. First off I could never get it to run in low RPMs in any gear but 5th. Even then when you eased on the gas it didn't really lug but it was more like it was underpowered until it dropped to a lower gear, but it only took half a second for this to happen. In 3rd and 4th if I trid to get it to go to lower RPMs by easing off the gas and slowing down it would just jump to 5th with the lower RPMs. For the most part it never dropped below 2k RPMs in 3rd or 4th. Don't know if all of this helps, but it doesn't sound like mine does what yours is doing. That being said, I really don't have any ideas on possible solutions to your issue. Have you tried driving it in manual mode for a while (keeping RPMs up above 2k) and then switch back to auto and see if it still does it. Let us know what you find out. Will
Will - thanks for testing yours when the weather clears - I'm anxious to hear what you find.
+1 to Vipers comments. These cars are very temperamental when it come to ATF. Hard to beleive that a small fluid variance causes issues. There are several threads here discussing fluid issues. I really never drive my car in full auto, but if it lets your RPMs drop to 1200 in the high gears, I would almost expect it to "lug" a little upon acceleration. In manual mode I never let the RPMs go too far below 2k. I will drive mine in full auto over the weekend (it's raining today and I just detailed the car last weekend...I know, I know) and see what kind of RPMs it runs at different speeds in the higher gears. Will
Thanks for the input. We did find that the ATF was a half quart low, and topped it off within a couple of days of the full ATF replacement. While overall it is shifting more smoothly, this did not fix the specific problem of the lugging/stumbling at low RPMs. Could this be a fuel/air oxy sensor issue instead ? We're going to hook up with the diagnostic system to look for codes next week.
there was no visible damage to the alternator, but that's not really relevant, and frankly neither was your comment. Does anyone else out there in RennTech land have experience with Tiptronic program malfunctioning and/or mechanical causes of the lugging/rumbling/stumbling I mentioned originally ? I'm experiencing this in 3rd, 4th, and 5th gears at engine speeds between 1200 and 1500 RPM. Thanks in advance for your relevant and timely responses. djm
Hello. I have a 2000 C2 Tiptronic (US) with only 30k miles. Just had the major service including ATF and a new alternator (failure due to 2mph rear impact by an SUV). Now noticing at low revs in 3rd, 4th and 5th in full automatic there is a shudder/rumble/stumble when opening the throttle slightly. When mashing the throttle it kicks down appropriately, and in upper rev ranges, it's smooth as can be. Is this more likely a tiptronic programming issue or a mechanical tranny issue ?