Hey Guys,

I have been doing a lot of research on my cylinder 4 misfires, (including studying ATLdisco's recent Misfire thread, which was very informative) but would like some opinions on where I should go next with my efforts.

For the last several months I have had 0304 usually accompanied with 0300 and for the longest time it also came with 1171 and 1174. I thought that it was a vacuum leak causing the misfires, so I just fixed the vacuum leaks which turned out to be from the injector o rings (in the last weeks before I fixing the vacuum leak, the leak worsened and I additionally saw 0171 and 0174 and at least four other cylinder misfire codes, not all correlated to the same bank)

I now no longer get any lean/rich codes but only get a regular Pending 0304 code often accompanied by pending 0300. I drove for 40 minutes straight yesterday and still only had the code pending. My UG informed me of it's "pending" every minute or so but never stuck as a trouble code.

This is what I have done already to attempt to fix this (all in the last 3000 miles):
New 8mm wires
New Plugs
New Air Filter
Cleaned the MAF (properly with MAF cleaner)
Cleaned my PCV system
Seafoamed

When I was doing the injector O-Rings I also switched injector #2 with #4 to help me determine if it was an injector issue (hoping the codes would move to 0302) ... no luck, still 0304.

So what would you guys suggest next? I haven't done the O2 sensors since I got the truck 3 years ago and I hope it is that.

Additionally, what is the danger of long term cylinder misfiring? Would I be ill advised to take the truck on a 1000 mile trip to Canada towing a thousand pound tent trailer next month?

Thanks guys, always appreciate the advice!

I'd check out #4 plug and wire for problems...... Bad crimp, loose connection, etc.
I know... New, but I'd check anyway

You probably saw my thread, too. It is embarrassing unless you know how little mechanical experience I have.

In addition to the plugs and wires... I finally solved my misfires and sluggishness by swapping a known good MAF into mine from a buddy's Discovery II. The difference was night and day and I had no codes from the MAF prior to the swap. I also had catalytic converter problems, but you probably don't. The MAF is a mystical device made from butterfly wings that can't be successfully cleaned. DiscoMike clued me in to that by phone and I thought it was a rubbish suggestion for about 10 seconds but, as always, he diagnosed my problem in less than three minutes and was perfectly correct.

Long term misfiring can put uburnt gas into your cats and potentially clog them, which is why I am shopping for new cats.

Thanks guys! That is good advice, I don't happen to have a good MAF lying around... but I will keep my eyes open for one. I will also be looking on the sparks and wires for a poor crimp!

I'm on the hunt for the cheapest, new, Bosch, MAF on the planet. I'll let you know what I find.