This just started happening today. I first thought that it was a problem with the transmission slipping, because it felt like it would slip then regain and keep doing that. But then I put the car in neutral and kept the engine at about 2500 RPM. Sure enough, after a few seconds it would hop between 2000 to 3000 RPM for about 3 - 5 seconds and then keep the desired 2500 RPM again. This happens when driving, but it doesn't seem like there is a certain pattern to it. Just happens every once in a while. Also, the "check engine" light turns on when it happens every once in a while, but then after the 3 - 5 seconds of engine RPM hopping, the "check engine" light turns off. What do you think this is? It's so inconsistent, doesn't always happen under certain driving conditions.
I assume its a late modle car with fule injection? If so you might want to replace your O2 sensor do a good tune up check your mass airflow sensor and your throttle position sensor. A vacume leak could also couse this. I hate chaseing down efi problems myself if this was carbed it would be ether a vac leak or maybe and ignition problem much easyer. IMO
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