Originally Posted by fluidmocean
It usually only does this lurching after about 20-30 minutes of driving. Once it starts, it does it under normal or hard acceleration and always around 25-30 miles per hour. The longer you drive, it starts around 45-50 miles per hour as well. The best way to describe it is that it feels like you are getting rear-ended.
Is it possible that this is a sign of a coil failing? That is the latest thought from Nissan.
It is currently at a private shop to see what they think.
So I'm going back to this statement because it gave me an idea. I seriously think you're engine is misfiring. I've experienced this before but in a different vehicle; i.e. 2002 Nissan Sentra GXE 1.8L automatic, but dynamics of how an engine work are the same regardless.
The Sentra's engine would run fine until it got warm then would start to buck if I pressed the gas pedal a bit to accelerate. Usually while under engine load would it buck on me. And it felt like a harsh repetitive surge motion similar to what you're describing. In this situation the ECU did throw a code identifying a misfire on cylinder #3. We looked at the coil, the plug, injector, and everything seemed fine. I let a mechanic friend look at it with one of his cylinder scopes; i.e. pull out the coil and plug and you look down into the cylinder itself. Turns out coolant (antifreeze) was dripping into the cylinder from between the block and head. BINGO, we found the cause of the misfiring.
We ultimately concluded the head gasket around that cylinder had allowed antifreeze to get into the cylinder itself which caused the misfiring. It didn't really happen until the engine got warm though. As any engine warms up, the coolant in the system builds pressure to about +/-15psi. If there is a leak in the system, the interior pressure will force the coolant out. If you have a head gasket leak around one of your cylinders, then it will result in misfiring.
I would highly suggest you get a cylinder scope and have each cylinder checked for fluid after you drive it. The back 3 cylinders will be a PITA to get to but it's necessary. Do the radiator 3 first as they're easy. After your engine warms up, you pull the coils, pull the plugs and take a look. If you see anything fluid inside the cylinders then that's the cause of your misfiring.
It's a thought that came to mind so I figured I would share. Might not be the cause of your issue but it's one thing you can check off the list.
Another possibility would be absence of spark due to shorting. While you're checking the cylinders also look for oil leaking into your spark plug tubes. The head covers for this engine have large/thick rubber rings that help to keep oil inside the head. These sometimes leak and will in some cases cause the spark to weaken as moisture in the oil will cause an electrical short from the plug terminal to the spark plug wall. I remember another forum member having misfiring due to this. He replaced the suspect valve cover and all was resolved. Here's a link that has a picture that describes oil in a spark plug tube (reference post #2 picture 8 of 10):
I'm absolutely amazed that seasoned technicians can't figure this one out. Maybe you can! We'll see...