Persistent intermittent missing on 3.0L v6
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Joined: Mar 2004
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Persistent intermittent missing on 3.0L v6
I seriously hope that someone can give me some direction. I'm at wit's end trying to resolve this issue.
I've got a 99 Ranger with the 3.0 V6, automatic trans, and 75K miles. About 3000 miles ago, the engine developed a persistent miss. It is noticeable at any RPM but most prevalently at around 55 MPH just after the trans has shifted into overdrive and the engine RPM is at it's lowest. (I don't have a tach so I can't give you specific RPMs). Also, the check engine light is on.
The code the computer is returning is P0300 -- the dreaded Random Misfire Detected.
With no specific cylinder to isolate to, I've changed out the plugs and wires. I also went through and cleaned and tested the following sensors:
Engine Coolent Temp
Throttle Position
Mass Airflow
Intake Air Temp
All tested within factory specs for ohm/volts where appropriate.
I've also cleaned the idle air control solenoid.
At this point, I've decided to start changing out sensors but I'd rather avoid that since they all test OK.
Where should I go next to diagnose this P0300 problem?
I've got a 99 Ranger with the 3.0 V6, automatic trans, and 75K miles. About 3000 miles ago, the engine developed a persistent miss. It is noticeable at any RPM but most prevalently at around 55 MPH just after the trans has shifted into overdrive and the engine RPM is at it's lowest. (I don't have a tach so I can't give you specific RPMs). Also, the check engine light is on.
The code the computer is returning is P0300 -- the dreaded Random Misfire Detected.
With no specific cylinder to isolate to, I've changed out the plugs and wires. I also went through and cleaned and tested the following sensors:
Engine Coolent Temp
Throttle Position
Mass Airflow
Intake Air Temp
All tested within factory specs for ohm/volts where appropriate.
I've also cleaned the idle air control solenoid.
At this point, I've decided to start changing out sensors but I'd rather avoid that since they all test OK.
Where should I go next to diagnose this P0300 problem?
Last edited by jgosney; Jul 12, 2004 at 02:44 PM. Reason: fix spelling
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Joined: Jun 2003
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Take a look at the EGR valve, pipe and passages. Also the the MAF is suspect. try tapping on it, but they may not find it. I have seen them replaced as a last resort to fix an 0300. Weak valve springs can do it, but at higher RPM the you describe. Carbon can build up on pistons and cause intermitent missfires, try a "decarbonizer" from the parts house. There is a thread about what ford recomends on the site to decarbon but I think its under pinging.. also the first sensor I would try is the cam position sensor, it can cause it. 0300 can be tuff.
Dave
Dave
Last edited by Dave257; Jul 12, 2004 at 07:20 PM.
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