Cold start misfire
 

I have a 2004 Santa Fe with a 3.5L and have recently developed cold start misfire. TDC codes are P0300-P0302-P0304-P0306. I have checked for spark arching, vacuum leaks, EGR valve appears to be working correctly. I have cleaned the throttle body, MAF sensor, and all of the usual things one might check, including coil packs, the plugs are firing fine, injectors are all firing fine. The car has a slight misfire that only lasts for a few seconds when you first start it, and then goes away as it warms up. It keeps setting those same codes. I have erased the codes after each test of suspect causes, which all turn out to be fine, to my knowledge. Any ideas on what could cause this on just bank 2? I don't know how to check the O2 sensor on that bank with a digital ohm meter. Could the O2 sensor possibly be the problem? Does anyone know how to check the O2 sensor with just a digital ohm meter?

I have worked on cars all my life, and I am stumped. Any help or suggestions would be greatly appreciated.

Thanks.

Did you check the wires? Also check the Crankshaft Position (CKP) sensor. I don't think the problem is the O2 sensors.

I started my car today after sitting for 3 days. The engine started to shake the car. Took the car to advanced auto they checked it out and said it was code P0302. And not to drive the car until it was checked out by my locan Hyundai dealer. Any Ideas of what it could possibly be?

I also have 03 and mine also throwing 2 5 and random misfire codswont pull itself hardley but i did see rhis last and have a feeling under car rusted bad there is a re gen box or something in middle of car bunch lines go to look like fuel rusted in two hanging down have feeling thia my prolem and your alls aswell

Many vehicles look great on the outside, but are a basket case on the underside where most folks don't look or wash.
If a vehicle is driven where road salt is used in the winter, that dust accumulates under the vehicle out of sight and goes to work rusting away parts without the owner knowing it.. Vehicles when purchased new should have an undercoating applied to help slow this down. They are using some protected metals and plastics, but they don.t do that much except reduce the weight of the vehicle. Regular maintenance is still required to help prolong the longevity of the vehicle. Under vehicle washing where salt is used, helps a lot..