first time user here and thanks for having me. now to the problem. 2 months ago, my 07 3.3 van through the p0305 code. pulled the plug and it was totally fouled with soot. the plug was a bosch platinum. through a champion copper in there and code did not recure until this week. pulled plug again and it too is fouled although not as bad. checked coil using a spark tester and spark is good. my question is can the cp be intermittently bad? or can it be bad only when hot as I tested it cold? not familiar with doing electrical testing. wires are new. would a bad injector foul the plug?

 

A sooty spark plug is indication of over-rich running after you've been on a run and got the engine hot. It should be pale brown. If it's white-ish, this shows a weak mixture.It used to also indicate burning engine oil, but you don't get much of that nowadays. Your motor is likely to be thirsty also.

Yes a bad injector can dribble and give poor mixing, but because of the homogenous mixing of a petrol engine, the plug fouling won't be all that bad.

If your lambda sensor is duff the micro. won't be able to get the mixture right and is likely to be rich.

If your engine coolant sensor is duff, the micro. will assume the engine is cold and keep the mixture rich. This may or may not show in the temp. gauge.

If the thermostat is jammed open* the engine will run colder and get a richer mixture. A giveaway for this is a poor heater.

Should be something to chew on there.

*Thermostats are arranged to jam-open if there has been overheating due to, say, a plugged radiator -- and that's usually caused by not replacing the antifreeze. The ally-core radiator corrodes and can't be flushed.

Leedsman.

 

question, what could be the reasons that when I do put in a new plug, I don't get the code for a couple months or so? also when I put in a new plug, she runs fine w/o throwing the p0305 code. if there is a misfire in that cylinder, shouldn't the code be present immediately and not wait until the plug is fowled to the point that she can't fire.

 

You're getting a misfire code because the plug is getting fowled and not firing over time. It's just taking a couple months of running to fowl that new plug to the point it won't fire. As stated, that cylinder is running rich or could be the plug is failing. Any signs of overheating on that plug? If the injector were leaking you'd have hard starts and/or a mileage drop.

 

does not hard start but mileage has dropped.