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Discussion Starter · #1 ·
So, for some background, I have a 2015 LX Coupe with the CVT. As long as I've had the car, I have noticed an occasional jerking sensation during a specific condition: When slowing down and coasting, such as approaching a red light, but then gently accelerating, such as if the light turns green as I approach it, I sometimes get a jerking sensation. In general, it only happens when the vehicle is going about 25-40 mph when I start gently accelerating. It may happen 2 or 3 times in a day, but then not happen again for several weeks. I've always felt that it had to do with the CVT attempting to change ratios abruptly when it was not supposed to, and I've suspected that it's not the CVT itself, but something feeding bad information to the CVT.

Now, it seemed to be doing it more frequently, so I decided to search beyond just this forum and do a Google search to see if anything comes up, and while I did not see my specific situation, I did see people report on similar scenarios, and they presented a couple different possibilities that I had not thought of before. I figured that it was either the throttle position sensor or a speed sensor feeding bad info to the CVT, but people have reported possible issues with a vacuum leak or a bad coil.

This makes sense. When I had my 1990 Ford Probe, I had gotten a tune up one time, and then I started getting this hard jerking sensation that I was sure was the transmission. My boss where I worked at the time (when I was installing car stereos -- he was very good at diagnosing problems like this) looked at it and saw that cheap spark plug wires were installed, and they were actually arcing to the engine under certain load conditions, causing the jerking. Upgrading the wires solved the problem. I believe we have coil-on-plug, so a bad coil could be a possibility.

When I had my 2002 Ford ZX2, I started to notice some very rough power delivery, so I pulled over and looked under the hood, and I saw an obvious hole in a vacuum hose. Temporarily taping over the hole (and then eventually replacing the hose) solved the problem.

This is where I'm looking right now. I checked the hoses the best I could, and saw nothing obvious with the rubber hoses. However, there is a kind of metal pipe vacuum junction on top of the engine, and I've got some rust there, so this is suspect. For now, I've wrapped some electrical tape around these pipes where the rust is, and so far, I have had very little of this jerking sensation. I've only driven it like this a couple days, so I'll see how it goes.

A vacuum issue also seems logical based on the conditions when this jerking occurs, that I described above, because in my experience, coasting produces some of the highest vacuum, which means that a small, intermittent leak will be more likely to be exacerbated under such conditions.

If anyone has any other ideas or input, I welcome your views!
 

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Discussion Starter · #3 ·
That's a good point. I think it's been about 2 years since my last CVT fluid change, so I'll get that done soon. However, I currently work at home and do not put a lot of miles on my car. It currently has about 97,000 miles on it.
 
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