2006 kia optima 2.7 runs good for few mins then misfires on 1 and 5 have changed plugs coils and crank sensor checked with carb cleaner for vacuum leaks no leaks whats the cause of the misfires

SOURCE: misfiring

if it were the cranksensor it would not start at all.you would have no fire.

SOURCE: crank sensor location on 2006 kia optima

in the tank

SOURCE: 2004 kia optima arcing around the coil pack

the coil pack mybe bad

ZJ Limited

• 17989 Answers
• Posted on Dec 30, 2010

SOURCE: FORD F150 4.6 L Engine

Several thnigs to check there; review all informastion disponible to do it and solve this...

P0356 - Ignition Coil F Primary/Secondary Circuit Malfunction
The ignition signal from the Powertrain Control Module (PCM) or Electronic Control Module(ECM) is sent to and amplified by the power transistor. The power transistor turns ON and OFF the ignition coil primary circuit. This ON/OFF operation induces the proper high voltage in the coil secondary circuit.

Symptoms
- Engine Light ON (or Service Engine Soon Warning Light)
- Lack/Loss of Power
- The engine may be harder to start
- Engine hesitation

Possible Causes:
- Open or short in the ignition coil circuit
- Ignition coil circuit shorted to ground
- Ignition coil connector
- Damaged ignition coil
- Damaged PCM or ECM

Possible Solution:
- If damage, repair ignition coil circuit
- Replaced ignition coil
- Replaced PCM or ECM
------------------------------------------------------------------------------------------------------------------------------------------------

P0152 - O2 Sensor Circuit High Voltage (Bank 2 Sensor 1)
The heated oxygen sensor 1 is placed into the exhaust manifold. It detects the amount of oxygen in the exhaust gas compared to the outside air. The heated oxygen sensor 1 has a closed-end tube made of ceramic zirconia. The zirconia generates voltage from approximately 1V in richer conditions to 0V in leaner conditions. The heated oxygen sensor 1 signal is sent to the ECM. The ECM adjusts the injection pulse duration to achieve the ideal air-fuel ratio. The ideal air-fuel ratio occurs near the radical change from 1V to 0V.

Symptoms:
- Engine Light ON (or Service Engine Soon Warning Light)
- High Fuel Consumption
- Excessive Smoke from Exhaust

Possible Causes:
- Harness or connectors (The heated oxygen sensor 1 heater circuit is open or shorted.)
- Front Heater oxygen sensor heater (Bank 2) may be faulty

Possible Solution:
Replacing the O2 Sensor 1 usually takes care of the problem
------------------------------------------------------------------------------------------------------------------------------------------------

P0174 - Fuel Injection System Too Lean Bank 2
With the Air/Fuel Mixture Ratio Self-Learning Control, the actual mixture ratio can be brought closely to the theoretical mixture ratio based on the mixture ratio feedback signal from the heated oxygen sensors 1. The ECM calculates the necessary compensation to correct the offset between the actual and the theoretical ratios.

In case the amount of the compensation value is extremely large (The actual mixture ratio is too lean.), the ECM judges the condition as the fuel injection system malfunction and light up the MIL (2 trip detection logic).

Symptoms:
- Engine Light ON (or Service Engine Soon Warning Light)
- Excessive Fuel Consumption

Possible Causes:
- Intake air leaks
- Front Heated oxygen sensor may be faulty
- Injectors may be faulty
- Exhaust gas leaks
- Incorrect fuel pressure
- Lack of fuel
- Mass air flow sensor may be faulty
- Incorrect PCV hose connection

Possible Solution:
Dirty air filter of faulty air flow sensor are common causes of the problem.
------------------------------------------------------------------------------------------------------------------------------------------------

P2197 - DODGE - Sys Too Rich at Hier Load Bank1
Means that the O2 sensors on each bank are seeing WAY too much oxygen in the exhaust gas. In normal operation the signal from the O2 sensors should swing back and forth between rich and lean. Your sensors are locked on lean.

Those codes are the same as P0174 (and P0171). Sounds like you have a vacuum leak somewhere. Most common place is the PCV elbow where it connects to the throttle body adapter.
------------------------------------------------------------------------------------------------------------------------------------------------


Hope this helps; keep in touch.

SOURCE: vehicle came in for check

A misfire at idle that smooths out at cruise is ALMOST ALWAYS caused by a vacuum leak. Take a hard look at your fuel trims at idle. If the Bank 2 Long Term Fuel Trim is more than + a couple points higher than the Bank 1 trim, your problem is most likely a vacuum leak. If the Fuel Trims even-out while holding the engine at 2000 RPM for about 20 seconds, then a vacuum leak is DEFINITELY your problem. I would suspect a leaking lower intake gasket leak because an upper plenum leak will normally affect all cylinders.