Random Misfire Code

[austinmob]

Had my truck into Ford to check out an engine light.. Comes up with a code for a random misfire.

The light came on about a month after i installed a new Camshaft Synchroniser and positonng sensor. Each time i reset the computer it usually comes on a few days later. So the misfire is not always there. The car drives like it always has and i certainly dont notice any misfire.

Any Clues guys?

 

[2000StreetRod]

Which engine?

Do you have the SOHC V6 that was available in Australia before it was available in the US?

Do you know the specific diagnostic trouble code?

I believe that two successive misfire drive cycles are required to set the check engine light.

Misfire is due to a lack of power or a bad sensor. The PCM computes the power of each cylinder and when one is low reports a misfire for that specific cylinder. Typical misfire sources are ignition, fuel injection and compression.

Ignition problems could be due to a bad plug, wire or coil.

Fuel injection problems could be due to a bad injector, pressure regulator, fuel filter or pump. The only problem that is cylinder specific is a bad injector.

Low compression could be due to worn/broken rings, worn or sticking valves, blown head gasket or cracked head.

 

[austinmob]

I have the V6 OHV 5 speed manual. I am leaning toward plugs and filters, i think they are a bit over due. I have had the truck 18mths and the previous owner did a major service before the sale to me. I havent touched any of it.

 

[2000StreetRod]

Read the codes

If you read the diagnostic codes you'll be able to determine if the same cylinder is misfiring. That would reduce the possible sources of the misfire.

If your engine is in good condition and quality plugs were installed by the previous owner the plugs should still be good. However, replacing the plugs will give you a chance to look for fouling on a specific cylinder and is fairly inexpensive.

 

[austinmob]

Problem solved "I THINK". The random misfire as interpreted through the computer was in fact just that. I was able to monitor the engine over a recent trip and found there was something strange going on under the hood. My suspicions were correct (so far). The misfire was a complete misfire off all cylinders at once meaning the problem had to electrical or fuel related. As the fault has only been occurring since i replaced the Camshaft Synchro and sensor cap i immediately sought technical info from a mechanic friend of mine. He suggested i put the old part back in and see what happens. I decided to only replace the Sensor cap.

Problem solved. No more Engine light coming on, no more random misfires and fuel consumption is back down to where it was over a year ago. Was 12.5 litres per hundred Kilometers, went up to 13.5. Now its back to 12.5

After inspecting both caps together i noticed the ford and US/chinese sourced part are identical with the exception of the Magnet inside the cap. The chinese part has a much smaller magnet. Now i would have thought that would mean nothing but obviously it does.

 

[austinmob]

Still no Check engine light. Purring like a kitten.

 

[2000StreetRod]

Congratulations!

Congratulations on solving the problem! Thanks for posting the solution so we all can benefit from what you learned.