My '03 4.0L ranger threw this code the other day. My scanner said it was a multiple cylinder, random misfire. Needless to say it is going in for warranty work at the earliest possible date. I was just wondering what might be the cause of a multiple cylinder misfire like this. Thanks!

 

Check out My thread. be sure to let us know what they find.


https://www.ford-trucks.com/forums/s...hreadid=191580

Dave

 

Here is what ford says about P0300 codes.

P0300 - Random Misfire

The random misfire DTC indicates multiple misfiring or the PCM cannot identify which cylinder is misfiring.

Camshaft position sensor (CMP), One or more EGR passages may be blocked or partially blocked., Low fuel: less than 1/8 tank., Stuck open EGR, Blocked EGR passage, If this is the case the Misfire Detection Monitor will indicate the EGR port to check for possible blockage.


Dave

 

Reset the light and drive it for a day or two. If it is a random problem it may not come back. If it is a real problem, the light will come back on. If it does take it back to the dealer.

 

The problem is not just a random failure, It is one that I can repeat at will. I took it into the shop the other day and they replaced the ignition coil and checked the fuel pressure at the rail to make sure everything was good. The problem is still there however, and it has a light on again. I think that it is the PCM, because it only does it in the upper RPM range of third gear (automatic trans) and nowhere else. Will be going back in on Monday.

 

What do you mean when you say it only happens at the upper RPM range ...can you actually feel the misfire? Does the engine buck or sputter?

Has to be related to either ignition or fuel delivery problems. So the dealer ought to at least check the CMP sensor, and probably should check the Crankshaft Postion Sensor as well. Maybe pull the spark plugs out to see if any of them tell a story about their respective cylinders. Check for bad plugs wires. And if your pressure is fine, then the fuel injectors should be checked. The PCM is one of the least likely things to go bad, although I agree you can't rule it out in this case, either.

 

Yea, I can feel/hear the engine mssing between 5000 and the shift point from 3rd to 4th gear. As far as checking things, I am going to leave that to the dealer, this thing is still under warranty, so I will let them do the work, that way if they mess something up, it is there baby. I do appreciate the input however.
What lead me to beleive that it was the PCM is that is will only do it between 3rd and 4th gear and nowhere else.

 

What was the outcome? I have the same problem on a '96 Chevy and we've replaced just about everything except the EGR valve and injectors.

Thx!

 

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laura joe--- GM issued a service buletin thats good for 100,000 miles for fuel injector malfunction on the 95-98 4.3, 5.0 and the 5.7. My dad had a 97 and he took it to the dealer about 5 times in 20,000 miles for plugged up fuel injectors, the issued that bullentin but he sold the truck do to its lack of reliablility. He used nothing but Unocal or Chevron gas so it odviously wasn't that.

 

Thanks for the reply! We did take to the dealer and they said the injectors were fine. We actually had 1 replaced within 3 mos. of buying the vehicle new! We've found some info on the web about a possible stuck EGR. We're going to try that this weekend. Will post results then! If it's not the EGR...the injectors are next!!

 

pull the codes before throwing parts at the problem.

 

P0300....a list of things to check!!

 

I found an article from this one random website helpful when i was diagnosing my 06' mustang's P0300. They seem to have posted essentially the same article for every vehicle but this is the one for the F-150. I got the most value out of the video at the bottom.