Check engine light?

Take the car to a nationally recognized parts store and have them scan the computer for codes. If the light is on, there should be a trouble code set in the computer.

Also, most parts stores will scan for free, so there is no money out of pocket.

Let me know what you find. Also, you mentioned the gas cap. Do you already know it is an EVAP code?

Joe

Check engine light on is an indication of a stored trouble code in the PCM
Need to use an OBDII reader to get in and read the codes
Most local shops and part stores can help you in getting the codes
You can post the codes for more help if needed
Check engine light on
1st step is to get the codes

When the light on go back to the part store ask them to get the codes for you
let me know what you have for codes
good luck

Diagnostic Aids
This test is used to diagnose the following:
Battery Terminal Condition
Keep Alive Power (KAPWR) Circuit Routing
KAPWR Circuit Condition
Faulty Powertrain Control Module (PCM)
Testing.

NOTE:KAPWR is interrupted when PCM or battery is disconnected. DTC P0603, P1605 or P1633 may be generated during next PCM power-up.

1) DTC P0603, P1605 & P1633:
2) Check Battery Terminals
Inspect battery terminals for corrosion or loose connection. Service as necessary. If battery terminals are okay, go to next step.
2) Check Engine Compartment For Proper Wire Routing

Inspect wiring harness and connectors for damage or corrosion. Ensure wiring harness is properly routed and not too close to ignition or exhaust components. Service as necessary. If no concerns are found, go to next step.
3) Check Keep Alive Power Circuit To PCM

Turn ignition switch to OFF position. Disconnect PCM connector(s). Inspect connector for loose, damaged or corroded terminals. Repair as necessary. Using a DVOM, measure voltage between chassis ground and KAPWR circuit at PCM harness connector terminal No. 55 (104-pin PCM), or terminal No. A44 (150-pin PCM). While observing DVOM, wiggle and bend small sections of wiring harness between PCM and dash panel. If voltage is continuously 10.5 volts or more, go to next step. If at anytime voltage drops to less than 10.5 volts, isolate open in KAPWR circuit and repair as necessary.
4) Check For Repeat Of DTC P0603, P1605 Or P1633

Reconnect PCM connector(s). Start engine and allow to idle and reach normal operating temperature. Perform KOEO ON-DEMAND SELF-TEST. Retrieve Continuous Memory DTCs. If DTC P0603, P1605 or P1633 is present, replace PCM. If any other DTCs are present, service as necessary. See DIAGNOSTIC TROUBLE CODE DEFINITIONS. If no DTCs are present, testing is complete. DTC P0603, P1605 or P1633 may have been due to a previous repair.
Good luck

Have the CAT convertor checked. It may be clogged or partially clogged.

They can perform a backpressure test on it, but it sounds to me like the convertor is clogged.

You should get a code.

If the convertor is bolted on, it is very easy (oops, I used the "easy" word :) )to remove and visually check it.

Otherwise check fuel pressure and spark.

Take the vehicle to a good autoparts store (autozone etc.) Have them scan for fault codes (most do this free) repost with the codes for a better diagnosis and repair advice

Codes will help in pin pointing the cylinder
plugs was changed what about the wires
if spark jumping out of coil and its strong coil should be OK

Check engine light:

Have the computer scanned for code/s-you have a problem within the engine management system that caused the CEL to turn on-This is your starting point of diagnosis, finding out what's going on.