P0306

[michibronc]

Hi All,

I was taking off after filling the tank at a gas station this morning. As I entered the expressway and got up to about 75 mph, I noticed the truck hesitating and jerking a small amount - but definitely noticeable. My Check Engine Soon light came on flashing and I'm thinking "son of a #$%#"! I pulled over, checked everyhing out - nothing apparent out of order under the hood. I made sure the dist cap was on tight and the wires were tight - nothing seemingly wrong there.

I turn the truck on again and the mil is still lit - but not flashing now. It wasn't running out of the ordinary so I drove home (180 miles). I did notice a little bit of hesitation when cruising at highway speed, but not quite as much as when the light came on.

Took the truck to autozone - they coded the problem (P0306 - Cylinder 6 Misfire) and reset the computer. I also dumped in some dry gas. No recurrence of the problem after about 10 miles of driving. I've looked up the problem online and have seen a recommendation to change the cap and rotor as well as the plug wires. One site even suggests that a bad O2 sensor can cause this code. Does anyone have experience with this problem? Can bad gas cause it? Just wondering before I start replacing things....

 

[Seabronc]

No experience with that code, but it could very well be high voltage arching when there is moisture in the air, probably wires. How long since they were changed? What was the weather like? You could try taking a squirt bottle of water out after dark and spraying around the wires, with no lights on, especially the ones in the #6 cylinder area. If they are breaking down, you should be able to see it. I'd do a basic tune up before going after something as remote as the O2 sensor, the reason that might be a possibility is that the computer adjusts the timing based on the O2 sensor input.

Good luck,

/emoticons/[email protected] 2x" width="20" height="20" />

 

[miesk5]

yo;

btw, I had one for 5...was a dirty FI connector.

for P0306, my info says;

Fuel injector or connector/wiring

Running out of gas, or poor fuel quality (nah...others would throw a code, right)

Fuel pressure (doubt it)

Ignition system

Evap system: fuel vapors leaking into engine (nah..)

low compression, valve train problems and timing issues (maybe)

leaking EGR valve or restricted ports (long shot)

The MIL will blink once per second when a misfire is detected severe enough to cause catalyst damage. If the MIL is on steady state, due to a misfire, this will indicate the threshold for emissions was exceeded and cause the vehicle to fail an inspection and maintenance tailpipe test

After cking #6's connector and wiring, and it is ok,

Look at this;

Pintle Crack pic & replacement part in a 92 351W Source: by Richard C

To test the #6 injector, swap it to another cylinder and see if the misfire moves to that cylinder.

& to see if 6 is firing use a long screwdriver and place it on 6 and listen for it firing; should hear a faint clicking this is the injector solenoid opening and closing.

also, Ford;s Injextors are the self cleaning type, but maybe....

 

[miesk5]

sorry Seabronc; I started my reply an hour ago and just finished it. Good read on da plug wires..etc.. I mis-read it, thought that stuff was changed/

 

[michibronc]

Good advice - thanks guys. I went ahead and changed the wires, cap, and rotor while I was in there. I took it for a lengthy drive to help a buddy with his snowmobile and back and no sign of the problem returning. I did lots of hard accelerating too. The truck seems a bit peppier now as well - the hesitation is totally gone. Not sure when the last owner did it, but it was all motorcraft stuff I took out, so it could have been the original stuff - there was a fair amount of wear on the rotor and cap contacts.

Hopefully just a friendly reminder to me to take care of the tuneup stuff.

Speaking of tuneup stuff, is there any sense in changing the O2 sensor as part of a regular maintenance schedule, or should I wait until it fails to change it?