1999 Toyota 4Runner

The check engine light tells you that there is a problem with your 4Runner. Please read the topic on the left "Check engine light" If you are close to Autozone Parts Store, they check it for you free using an OBD scanner. The OBD scanner gives a trouble code which usually starts with P0. That code gives the causes why it is misfiring. Put another topic regarding this trouble code and surely fellow members here can help you pinpoint your problem. You said that check engine light goes on and off. Sometimes, even when the light turned off, the problem is already stored in the ECM computer of the car. So, you can still use the OBD scanner to check the trouble code.

By the way, bad spark plug wires causes misfire. If it does not work, it might be a defective igntion coil for number 4. But start with the trouble code first from the OBD scanner.