Rumblin, Bumblin, Stumblin in Higher Gears at Low Rev

[djmayers]

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 ?

[RFM]

The car have got a rear impact, and only the alternator have damage? I should the car inspect more punctual if i was you.

[djmayers]

The car have got a rear impact, and only the alternator have damage? I should the car inspect more punctual if i was you.

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

[viper501]

Given the temporal connection between the ATF service and the problem, I'd suspect that there may not be enough fluid in the transmission. I'd check that first. If it is low, you might be OK with just adding additional fluid but I'd document it with the dealer who did the service in case there is latent damage to the transaxle.

[whs]

Given the temporal connection between the ATF service and the problem, I'd suspect that there may not be enough fluid in the transmission. I'd check that first. If it is low, you might be OK with just adding additional fluid but I'd document it with the dealer who did the service in case there is latent damage to the transaxle.

+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

[djmayers]

Given the temporal connection between the ATF service and the problem, I'd suspect that there may not be enough fluid in the transmission. I'd check that first. If it is low, you might be OK with just adding additional fluid but I'd document it with the dealer who did the service in case there is latent damage to the transaxle.

[djmayers]

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.

[djmayers]

Given the temporal connection between the ATF service and the problem, I'd suspect that there may not be enough fluid in the transmission. I'd check that first. If it is low, you might be OK with just adding additional fluid but I'd document it with the dealer who did the service in case there is latent damage to the transaxle.

+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

[djmayers]

Will - thanks for testing yours when the weather clears - I'm anxious to hear what you find.

[viper501]

I'd be surprised if there was a CAT / MAF issue without a CEL. You can hook it up to a OBDII reader and see what values you are running. I'd keep checking the ATF levels after the transaxle gets warm to ensure that you have fully filled it. I'm almost afraid there may be some internal damage, such as to a torque converter, from running it low.

Another question is whether the car is 'stuck' in manual mode? Again, don't have too much experience with the Tip cars but just a thought.

[whs]

Will - thanks for testing yours when the weather clears - I'm anxious to hear what you find.

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

[djmayers]

Will - thanks for testing yours when the weather clears - I'm anxious to hear what you find.

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

[djmayers]

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. :)

[WEL996]

I have a 2002 C4S Tiptronic with just over 24,000 miles. Bought it about a month ago and the car seems largely under maintained. It recently started the "rumbling" thing at low RPM's in higher gears. Shifting seems to be at ridiculously low RPM to begin with. In auto mode car will go into 5th gear at 30 mph. In 3rd or 4th gear if you give it gas while below 2,000 RPM it is more of a clunking rather than a rattle. Above 2,000 RPM everything is fine. 1st gear is fine at any RPM. Sometimes a rough shift into and out of 2nd gear. ATF fluid? Certainly, the engine is bogging down substantially but the transmission is failing to properly down-shift.