99 I30 rpm surges up and down at idle

[craftm]

Have a I30 99 surging up and down at Idle, sometime it will shut off . Starts up fine runs for a few minutes start to surge again . No code , check vacuum lines for leaks . Has a K&N air filter in the air box. Thanks for the help

[NutriaforBreakfast]

It could be several things but you might check these first;

http://www.nicoclub.com/FSM/i30/1999/ec.pdf

1) Idle air control valve (EC-374 or page 376)
You can check the resistance of the item. Also there may be some carbon
causing the valve shaft to not move or stopping it up. Remove the "cage"
with a screwdriver and clean out the carbon with mass air flow sensor cleaner.
I bought some dental probes at Harbor Freight and GENTLY pick it out too

2) Throttle position sensor (EC-160 or page 162)
I would first try removing the harness connector and rev the engine up and down
several times and reconnect it. This might allow the ECM to "relearn"

If this doesn't work the you can test the resistance with a multimeter
Note the resistance of the item changes as the throttle body opening changes

Good luck