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Discussion Starter #1 (Edited)
There seems to be multiple causes for the over-taching where MO barely moves, and some are easy fixes and some aren't The following method may not work for everyone.

For those who don't want to read the entire post, here's the condensed version: If your car hasn't been started for 24 hours, let it warm up for at least five minutes (the longer the better). If you park outside and it's very cold, you may have to let your car warm up much longer. When first driving, keep the RPMs below 2500 until 20MPH is reached (I actually prefer to keep the RPMs at 2000). Once at 20MPH, you can feel the tranny make a gear change and the RPMs will come down and you should be able to reach any speed more normally from that point on. But, if you have to stop or slow below 20MPH before driving at least 40MPH for about five miles, you'll have to use the same process again until you hit 20MPH. If you've driven at least 40MPH for about five miles and then stop or slow below 20MPH, you should be good to accelerate to any speed normally.

The long version...

In reading some of the issues other owners have had with their CVTs (particularly the over-revving with very little acceleration) I'd be curious to know what those drivers did once faced with the problem. In many cases, it seems they replaced the CVT or valve body or step motor (or this or that) and sometimes it worked for a while and sometimes it did nothing (except for replacing the entire CVT). When they first started experiencing the "high RPM, low acceleration" problem, did they try to accelerate through the problem, keeping the RPMs above 3000 or greater? Did they ever try to back off on the gas and possibly feather the pedal and be patient and let things warm up for a while to see if MO would drive more normally afterwards? I suspect that if you try to force MO to go fast when she's not ready, that act may somehow cause damage to certain components (especially if lack of fluid/fluid pressure is the issue) which may cause the CVT problem to get worse and become irreparable and make MO inoperable.

I'm going on 3.5 years with the "cold CVT" problem that requires I let MO warm up for about five minutes, then when driving on a flat road don't exceed 2500 RPMs until the 20MPH mark is reached, then the RPMs drop, then I can proceed to 30MPH and 40MPH fairly normally without the RPMs becoming excessive. So, 20MPH is the first magic number, and once I've driven at or above 40MPH for a little while, it's usually smooth sailing. The exception is a day with temps below 40 degrees. Even if I've driven for any hour at 55MPH during a cold day, I might (sometime) come to a stop or slow-down, then go to accelerate, and the acceleration lags behind the RPMs a little. It's like the engine is on crack and the CVT is just waking up and realizing it's time to go to work - the two components just aren't in sync. Something tells me it's not a throttle position sensor issue. I think it's possibly one of the tranny pressure solenoids acting up or a speed sensor. I know on rare times when that happens, I simply have to pull over, turn off the engine and turn it back on and MO drive’s fine again. So, because of that, it doesn’t seem like it’s 100% heat-related either, where once something is warmed up everything’s good. However, during the hot Summer months, I only have the over-revving problem after first driving MO cold. I don't recall having the issue of random over-taching after an hour of driving.

Now, if it’s the first cold start of the day, and I let it warm up for five minutes and then drive on a flat road for a ¼ mile to reach 20MPH, then I drive another ½ mile at 40MPH and then come to a stop, I still have the same issue of having to prevent the RPMs from over-revving to 3000 while I reach 20MPH. Even driving at 30MPH for five miles in cold temps and then stopping doesn’t always make MO drive fine. The second magic number seems to be 40MPH, since once I drive at least 40MPH for about five miles, everything is typically fine and I’m not stuck nursing MO from a stopped position to 20MPH…I can just accelerate normally. Recently, I started MO and let her warm up as I blew the leaves off of the driveway. 20 minutes later, I drove away and noticed that she went to 20MPH more quickly, without seeming to want to over-tach. To be clear, the driving 40MPH or higher for five miles is only needed to prevent you from having to nurse MO along again if you stop or slow to below 20MPH. If you've reached 20MPH and never have to stop or slow below 20MPH, you should be fine going at any speed until you run out of gas. :) Note that my car is garaged, and there's a furnace in there that keeps the garage above freezing. So, I don't know how severe the CVT problem could get if I had to leave MO parked outside overnight in cold/freezing temps. Perhaps I’d need to let MO warm up for 30 minutes. Maybe that's what others have experienced and why they sometimes paid a lot to replace the CVT. Perhaps it seemed like the CVT was a total loss and there was no way to drive it. However, maybe under very cold, overnight parking conditions, the simple act of starting MO cold could cause (or start to cause) permanent damage to certain tranny parts, and so those CVTs eventually fail.

Scenario #100... it's a 60-degree day. MO was driven for two hours above 40MPH, and has been stopped/parked for the past five hours. I start MO and let her warm up for five minutes, at which point I am immediately confronted with a small hill. Refer to the attached pic to understand what I'm about to say. If MO is five-minutes warm but hasn't reached 20MPH yet, and she's stopped at the start of that guardrail where that slight incline begins, it would be very difficult to get MO up that small stretch of slope because the RPMs would want to exceed 3000, but MO wouldn't have the increasing speed to make it up there, at which point I'd have to turn around and go back down and drive around for a bit, and hopefully go down a hill that would help assist in reaching 20MPH and then 40MPH. Once MO has reached the magic numbers and was driven for about five miles, I could stop at that same place and then go without any issue. Likewise, if the road leading up to the start of the guardrail was flat or downward, and MO was started cold but was able to hit 20MPH before reaching that spot, she'd have no problem continuing on her way up that entire stretch of road at any speed above 20MPH. Just sharing some insight into my CVT issue so maybe someone can figure out what's causing it, and maybe learn how to work through it in order to keep driving MO.

The reason I’m posting this is simply in case others experience a similar problem and don’t have thousands of dollars to throw at repairing it. Perhaps an extended warm-up period, combined with a bit of patience while reaching 20MPH, can allow them to still drive their car without having to spend a lot of money.

For reference, I have a 2003 AWD SE and I'm the original owner. More than five years ago, I installed a used CVT from a 2006 MO that had 120,000 miles on it. I've since put an additional 166,000 miles on it. With this used CVT, instead of using the Nissan-specified tranny fluid, I filled it with Castrol Transmax Dexron VI. During the past 3-4 years, I've thrown the P1778 code about 10-12 times, and once I got some code whose number I can't remember that I think my OBDII reader described as a "critical CVT failure" or something (that code appeared about three years ago, but MO drove fine for the next five hours of my trip and that code has never returned). Also note that over the past 3.5 years, the CVT problem has not gotten any worse. The only noticable performance changes I ever see are during seasonal transitions from hot to cold and vice versa.
 

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