05 Santa Fe GLS 3.5L Misfires
 

My wife's 2005 Santa Fe GLS 3.5L is misfiring pretty badly. Codes are showing random misfire (p0300) and misfires on all 6 cyliders(P0301, P0302, P0303, P0304, P0305, P0306). It is also getting a primary/secondary ignition fail(p0350). In addition to these codes, the tachometer now only works intermittently.

I have checked/replaced the vacuum hoses and replace the EGR valve with no improvement.

Does anyone have any ideas what the next step would be? I'm thinking that a bad coil pack would just not fire at all and a bad coil/plug or wire would not cause misfire on all 6 cylinders.

Any help is greatly appreciated.

Thanks.

After looking at some different posts both here and in other Hyundai forums, I disconnected the MAF sensor and the misfires ceased. I got some MAF cleaner and cleaned the MAF sensor and changed the air filter. I cleared the codes that the disconnected MAF had tripped and plugged the sensor back in. On test drive the misfires returned. Replacement MAF sensor is around $200 and some posts about MAF on the forum suggest that the sensor doesn't go bad that often. I don't want to drop two bills on the new part and have the same issue.

Anyone have any guidance?

Thanks,
Jeremy

I would pull the small timing cover and inspect the belt and make sure it's tight. Look for a missing tooth on the belt. Sometimes a tensioner will go bad. Use a flash light and inspect the wires going to both the camshaft and crankshaft sensor. may be pinched or insulation coming off wiggle plugs. Use a logic probe and check for pulse should be a black wire.
Camshaft position sensors are a frequent problem on the 3.5L engines
http://www.ebay.com/ search 271589376997 these are computer safe.

This is probably the engine misfire sensor which is located on the driver side of the engine just below the throttle air intake tube and if I remember correctly it is mounted on the transmission housing very easy to see and access. Google it and you'll get some pics... This sensor will go out and you will get the misfires on all cylinders and your tachometer may not function. The sensor performs a dual function and running the tach is one of them.