P0300 code????

Just got back from a 700 mile trip with my 02 AWD Astro pulling a 2500 pound enclosed trailer behind it. About 300 miles into the trip the engine light came on and stayed on for the duration of the trip. I did pull through some pretty hilly terrain for about 150 miles prior to the engine light coming on and on some hills I did use the tow button when taking off. When I got home, I unhitched the trailer and went out to pick up a few things. When I came out of one store I noticed the engine light was no longer on. I don't know if towing the trailer had anything to do with this. So I plugged my code reader into the van and got a P0300 code - Random/Multiple cylinder misfire detector. Also got fuel sys1 and fuel sys2, OL, drive conditions.

The van is equipped with a towing package that has tranny and engine oil coolers. Temp and oil pressure were normal for the whole trip, the only difference is that I was doing about 14 miles per gallon compare to the 18 to 20 I usually get without the trailer.

Can anyone tell me if there is something I should check? Would the fact that I pulled that trailer have anything to do with it? Should I worry about this?

I replaced the complete ignition this spring, including a new distributor, also replaced the cat converter in march of this year. The van runs only on Castrol Sythetic 5W30 oil. Tranny, transfer case and diff fluids were changed over the winter.

Thanks for any help!

What distributor cap did you install?

All ignition components are AC Delco and were replaced in March of this year. Distributor itself was replaced in May of this year. I just find it wierd that the engine light went off shortly after I unhitched the trailer????? I never had any issues towing before. I know I had distributor gear issues a couple of months ago, the gear was wearing. Should I pull the distributor with this code and see if the gear is worn again? The light has not come back on and it has been 3 days of about 200 miles each day.

I wasn't really thinking about scatter or CMP problems from distributor or driven gear wear. I was thinking more about compression blowout from weak spark. With the additional loading from towing, the higher cylinder pressures (BMEP) sustained for a longer period (due to increase load at lower engine speeds) could cause spark blowout by compression. A slightly weak ignition system could be responsible.

Remember that the PCM monitors for misfire by measuring the interval between sparks averaged over the RPM rate of the engine. If one cylinder produces less power (misfire) there will be a longer interval before the next cylinder fires (since the "misfiring" cylinder did not make equal power). Random misfire means that the PCM is detecting this condition among more than two cylinders, and in no particular order. weak spark, as well as other factors, can cause this.

Those other factors can include low or marginal fuel pressure or fuel flow rate, excessive internal friction, restricted intake air flow (which may also trigger a lower MAP/higher vacuum code), or engine mechanical problems.

FWIW, you can use whatever you like, but unless you are using European imported Castrol Synthetic, you are NOT getting true PAO synthetic in Castrol bottles. I just hate to see someone pay more for something they're not really getting. Because the Federal Trade Commission in the U.S. has no backbone, hydrocracked mineral oil is allowed to be called "synthetic" and sold here as such. European countries have more sense in that regard, and don't allow that. Only PAO, POE, or silicones are allowed to be sold as "synthetic" there, and thus Castrol sells real synthetic in Europe and fake synthetic here under the same name.

Should I look at getting a stronger coil to increase spark strength? Or is there something else I should look at to increase spark strength?

It's hard to understand why they say they are selling you full synthetic oil, what a bunch of crooks! Is there a brand I should switch to to make sure I get full synthetic? I heard a lot of good things about Royal Purple, what do you think of that oil?
Thanks!

A stock coil should provide more than adequate spark energy if everything else is intact. Before just replacing the coil, you can test it.

It would also be a good idea to check the spark plug gaps and condition. Even though they are new, they must have the proper gap set before installation. Excessive gap can allow spark blowout just as easily as a weak ignition coil.

Fuel delivery is also in question, but if there was no noticeable stumbling or lack of power while you were towing, that is probably not as likely. Of course, checking the air filter is easy and should be a first step. While the filter box is open, you might want to look at the MAF inlet for excessive dirt or contamination. Do all the easy things before replacing anything.

As for the engine oil, the last I checked, Royal Purple, Red Line, Amsoil, and Mobil 1 were still PAO base stock lubricants, not hydrocracked mineral oil.