[2old2rocknrollhy]

My nephews 2002 hyundai elantra started to intermittently misfire. It smelled
like rotten eggs he said. No OBD codes or check engine light. It has new exhaust,
cat and O2 sensors.

Looked car over found gas leak. Repaired gas leak and problem returned.
Cleaned Idle Air control valve with mass airflow cleaner. Car runs a lot better
and throttle response is way better. This was a intermittent problem, so time will tell if cleaning IAC valve was the fix.

 

[sbr711]

IAC wont cause random misfire..

Look for aged wires with strange lightning strike type burns/cracks at the plastic ends that set on top of spark plugs.. aged plugs, NGK Platinum is a 60,000 interval.. arc from coil tower where plug wire attach.. cracked intake manifold gasket is quite common on XD 2.0L

 

[2013migt]

My nephews 2002 hyundai elantra started to intermittently misfire. It smelled
like rotten eggs he said. No OBD codes or check engine light. It has new exhaust,
cat and O2 sensors.

Looked car over found gas leak. Repaired gas leak and problem returned.
Cleaned Idle Air control valve with mass airflow cleaner. Car runs a lot better
and throttle response is way better. This was a intermittent problem, so time will tell if cleaning IAC valve was the fix.

Does this problem occur when there is high humidity or rain, dampness ?

Check for cracks in the ignition coils, look with a magnifying glass, the cracks will be seen better this way.

When it is damp outside, run engine at night, and see if you can see the high voltage arcing for your source of the trouble.

 

[2old2rocknrollhy]

My description of the problem was not correct. I talked with my nephew again and he said it wasn't a misfire.
It was a lack of response (hesitation)when giving it gas.
It was like it wasn't getting gas. Then we found the gas line leak and fixed the leak.
Thought it was fixed, but it happened again just not as bad. After cleaning the IAC valve, no hesitation.
When press down on the accelerator it goes.

Sorry for the confusion

Tom