Help me please! Misfires ugh

[lburnham84]

I have had the same problem for MONTHS. I have codes p0301 p0302 and p0303 and no other codes. What would cause these codes and no other codes? I'm stuck and have no clue where to begin. I don't have the money to take it to a mechanic. Any help will be MUCH appreciated. Thanks

 

[muhl5443]

Tests/Procedures:

1. Since all of the codes are generated for bank 1 of the engine, there is a possibility that there is a cam timing issue.

2. Install a vacuum gauge to check for lower than average vacuum. Typical vacuum at idle would be approximately 18 inches at sea level.

3. Pull the spark plugs on both banks and perform a compression test. If the compression on all of the cylinders on bank 1 is lower than the cylinders on bank 2, the timing chain has probably jumped time.

 

[muhl5443]

1. Check the input of the #11 O2 sensor on the scan tool. With the Key On, Engine Off (KOEO) the voltage of the sensor will typically read less than 0.1 volt. If the sensor is showing a reading of greater than 0.5 volts without starting the engine, disconnect the #11 sensor and look for the reading on the scan tool to drop to the low expected value indicating a defective (shorted) O2 sensor.

2. If the sensor input is showing a normal value, remove and inspect the condition of the passenger side spark plugs. If all spark plugs look dark or wet fouled, check compression readings of at least one cylinder and check compression on a cylinder of the driver's side of the engine for comparison.

3. If compression readings between the two sides of the engine show larger than a 10% difference, service the timing chains, tensioners, and guides for mechanical failure. Since the passenger side camshaft is driven by a chain at the rear of the engine, the engine must be removed to access and service the chain cassette.

4. If compression readings appear to be equal between the two sides of the engine, check for a possible exhaust backpressure issue with the passenger side of the engine and service the catalytic converter as necessary.

5. If one of the three spark plugs on the passenger side is sooted or wet-fouled and the other two are dry, check the fuel injector of the rich indicating cylinder for mechanical failure or an issue of the wiring harness or PCM keeping the injector open at all times.

 

[muhl5443]

1. Install a vacuum gauge and monitor the gauge as the problem occurs.

2. If the vacuum gauge needle quivers as the misfire occurs, the problem may be due to defective valve springs.

3. Ford has issued out Technical Service Bulletin 02-03-02 for engine misfire above 4800 RPM to replace the valve springs with updated valve springs.

This is a partial text from Ford's web site: DIAGNOSTIC TROUBLE CODES (DTC) P0300/P0301 STORED IN MEMORY - VEHICLES EQUIPPED WITH 4.0L SOHC ENGINE ONLY: VERIFY THAT THE DTC SETS ONLY AT 4800 RPM OR HIGHER. REFER TO THE TSB FOR DETAILS. SOME VEHICLES EQUIPPED WITH THE 4.0L SOHC ENGINE MAY EXHIBIT A CHECK ENGINE LIGHT "ON" WITH DIAGNOSTIC TROUBLE CODES (DTC) P0300 (RANDOM MISFIRE) OR P0301. THE DTC WILL SET WHEN THE ENGINE IS OPERATED AT HIGH RPM'S (4800 RPM AND HIGHER). THE MISFIRE CODE RESULTS DUE TO SYSTEM INTERACTION OF HIGHER THAN EXPECTED TRANSIENT EXHAUST SYSTEM BACKPRESSURE (UNDER HEAVY ACCELERATION) COUPLED WITH VALVE SPRING RESONANCE POINTS EXPERIENCED AT THESE ENGINE SPEEDS. THIS INTERACTION MAY CAUSE THE EXHAUST VALVE TO HANG OPEN AT ENGINE SPEEDS OF 4800 RPM AND HIGHER. VERIFY THAT THE DTC SETS ONLY AT 4800 RPM OR HIGHER. REMOVE CURRENT INTAKE AND EXHAUST VALVE SPRINGS AND REPLACE WITH NEW SERVICE INTAKE AND EXHAUST VALVE SPRINGS. REFER TO THE TSB FOR DETAILS.