I have a chevy venture '00 with 70k miles. Everything worked perfect until yesterday. I took the exit at the highway and cruised in a little town. When I tried to pass a car and gave more gas, the car started to buck. I saw the RPM gauge going like crazy, from 1500 to 3500. A kickdown on the pedal solved the problem for a few sec. It shifted back to its lower gear and after that I could cruise in the 5th gear. But when I decreased speed, and wanted to give a bit more gas, it started again. Seems that it is begining to buck while it tries to shift from 1-2 2-3 and so on. no check engine light, only the battery icon lit up and went out. finally I stopped and put the car in neutral. I pulled the throttle cable and let the car reach about 4000rpm. Nothing, engine runs smooth. No hickups, no rough idling nothing. I refitted the MAF sensor cable just in case. Now check engine light lit up. the car stalled, and I started it again. Runs great. See a little fluctuation in the RPM. Normally it idles at about 600-700rpm. Now it runs between 700 and 1000rpm.

Drove to a shop and read the codes.
Replaced the possible issues.

- MAF sensor
- Oxygen sensor (upstream)


This morning I drove 25 miles no problems at all. Only one little hickup. Left the car alone on the parking lot, and when driving home problem came up. Stopt the car and pulled of the o2 sensor connector. started the car and problem still excists. It seems that when I kick down the gas pedal, it hasitates again, but doesn't show a hickup above the 4000rpm.
You can see on the movie that the rpm is fluctuating. It looks like the car is going to stall, but the computer keeps it running. Any idea. Could it be a fuel problem, EGR problem, as the scantool doesn't show any other problems.


made a small movie so you can see the rpm gauge fluctuating heavily
http://www.youtube.com/watch?v=RzHng60GZew

 

Did you ever get this sorted out? I have a simular problem.
Thanks

 

I figured out that it was a fuel issue. As I´m in Europe I gave my chevy some higher octane fuel. We use 95, but I went for 98. Problem dissappeared afterwords.

 

That sounds as much like water in the gas as anything to me. Low octane will usually cause pre-ignition or knock.