Ok, Since the check engine light is coming on and off, this should aid in the diagnosis of the concern. You can run a test of codes by jumping the self test connector under the hood as shown in this attachment. Once you know what codes are stored it should help aid in the diagnosis of the concern. Ignition coils are common failures in the ignition system.
During Self-Test, service codes are displayed by the "Check Engine" light as a series of flashes. For example, the single digit 3 will appear as three flashes. Because service codes are represented by two digit numbers, a code of 23 will appear as 2 flashes, a 2 second pause, then 3 flashes. When more than one code is present, there is a 4 second pause between codes.
Continuous Memory codes are separated from KOEO codes by a 6 second delay, a single half second flash, and another 6 second delay. Continuous Memory codes are displayed in the same format as KOEO codes.
- Perform all safety steps required to start and run vehicle tests -- apply parking brake, place shift lever in "P" (A/T) or neutral (M/T), block drive wheels, etc.
- Turn all electrical loads "OFF," including radio, lights, heater and A/C blower fans, etc.
USING "CHECK ENGINE" LIGHT
Using "CHECK ENGINE" Light
No special equipment hook-up is required to read service codes with the "Check Engine" light. To activate the system, connect a jumper wire between Self-Test connector signal return pin and self-test input lead as shown on image.