Fluctuating RPM

[brokepathy]

I have a 2007 Nissan Pathfinder. I just recently had the Transmission Rebuilt due to the fluid leak issue. When I drive the car it will drive flawlessly for the most part. The problem comes when I am cruising and I'm at around 2000 rpm and I slightly accelerate. The problem is at around 3,000 rpm the engine will lose power and then surge back up again in rapid succession. It will lose 500 to 1,000 rpm at a time and then it comes back. If I back off the accelerator it will stop surging and if I press the accelerator more it will stutter once and then stop and increase speed as normal. Originally I thought it was a transmission issue but I have taken it back to the shop several times after it happens and they ran countless test and test drives and they concluded it is not the transmission. They said it might be an electrical or sensor issue. Which I believe because the transmission shifts properly even after the stutter.

Last night I was driving home after picking up the truck from the shop. It was driving fine until the truck decided to increase to max RPM's on its own. As soon I felt and saw RPM's spike I took my foot off the pedal then the transmission try to catch up by downshifting. But since I took my foot off the accelerator it just bucked spun the tires slightly and then the truck was back to normal. It turned on the SES light after it happened. I was about 10 minutes from my home when this happened so I continued to head home. On the way home the VDC light and the Slip light both turned on and stayed on until I park. After I parked in my driveway I shut off the truck and started it again. When it started the VDC light and Slip light were no longer left on. But the SES light is still on. I have search everywhere for an answer and havent been able to find anything on this. Any insight would help. I will try to get the codes pulled this evening and update with the codes pulled.

Thank you in advanced.

[brokepathy]

I wasn't able to get the scanner yesterday. May have to wait till the weekend to buy one. Has anyone heard of this happening?

[4xq]

Advance Auto will hook a scanner up for free and read the codes. They scan engine codes only. You might as well find out what codes are lighting up the SES light.

Transmissions set codes as well - you may need to read codes for the powertrain which is a much more expensive scanner. Very few scanners have that capability.