That annoying little sticker in my windshield is dated 9 of 13.

That said,

0455 (evap leak)
0300 (multiple misfire)
0301 (cyl 1 misfire)
0303 (cyl 3 misfire)
0305 (cyl 5 misfire)
1282 (fuel pump circuit logic error)
0351 (coil drive error)

I know 0351 is because I'm running an MSD. I'll have to revert back to stock config to remove it, i'm sure.

0455 has been there for several years. One day I'll replace all those cracked lines.

1282, I have NO earthly idea where that came from.

As for the mis-fires I have no idea. I have an exhaust leak on the right side (need to tighten the connection on the manifold/Y-pipe) that may be triggering it, or the left bank mini-catalytic may be melted/clogged. That's the only two guesses I have.

MAP is reporting 4.5-6 PSIa (21-18 inHg) at idle and 11-13.2 PSIa (8-3.6 inHg) at WOT, via my ultra-gage. So that seems to be normal, no excessive vacuum leaks. Oil is fresh (went from 10w-30 to 10w-40, oil pressure went up accordingly). All four O2's swing all over the place, from .940 to .120 volts, can't seem to stay happy with any number.

Also, been going without A/C. Finally put some gauges on it today, and response at kick-on is slow. Condenser instantly gets hot, but the pressures take about 2 minutes to respond, then the compressor starts making a bunch of noise once they get to the normal range. $300 labor and $370 in parts (new/not-rebuilt denso compressor with oil, new oriface valve , and 4 cans of R134a).

 

Just wondering if you need to clean your fuel injector components. My 3.9 periodically throws the same codes. I just reset them and move on. You are probably much more of a mechanic than me, but in my simpleton mindset it sounds like something common to that bank of cylinders, and my guess is it is fuel pressure related, maybe not the injectors themselves.

I've put several cans of injector cleaner through mine, and I'm waiting to see if it comes up again. If so, I'll probably have it checked out.

I've sort of ruled out ignition issues because I've already replaced plugs, wires, cap and rotor on mine, and I can't imagine anything further back from that point that would always and only affect that bank of cylinders.

 

Mis-fire codes are set 2 ways: timing between the 6 TDC timing marks on the flexplate, and through the O2 sensors.

The 6 TDC marks are 60 degrees apart. As the crankshaft turns, the time between each mark should be the same. But if that time frame shifts- one mark is late and another is early- then the computer knows one cylinder is not making full power, and will throw a misfire code.

If the O2's indicate a particularly off-lambda condition, they will throw a misfire code, presuming that one or more cylinders are not fully burning.

Cylinder pressures and exhaust back-pressures can affect the misfire codes. If one exhaust side if more free-flowing, that bank of cylinders will accelerate faster, and the time frames will shorten on that bank, while the other bank lengthens, thus throwing a code. Likewise is a cylinders(s) has/have low pressures, then they will accelerate quicker from a lesser load.

My O2 voltage readings are all over the map, MAP is not indicating any kind of vacuum leaks. I do have a loose flange/exhaust leak on the right bank (which would make the left bank seem lazy to the timings) that may or may not be a culprit. I don't have nor know anybody that has the equipment to do a live scan.

 

Anybody know where I should start, other than replacing all the vacuum lines going to the charcoal can and fuel tank?

I don't think the O2's are bad, so I'm not sure what is throwing the misfire code. I figure all I can do is switch from MSD to PCM drive, throw the 87 tune in it, and see how far I get.

 

Well, cleared DTC's with the SCT and got the light to stay off. Failed due to a bad gas cap. That said, I noticed that the O2's weren't quite right after shutdown, after seeing that they had issued a "not ready". I'd just done a 50 mile drive, there's no question in my mind that they should have been ready....took about 30 seconds after shutdowm to go normal.

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Thanks, Magnethead.

A little update on my 3.9....I took it in this week for various maintenance items, told them about the codes, and asked them to take a look. I had cleared the codes from the last event (out of habit) but they determined that the distributor timing was a little off. It seems they pulled the distributor about 9 months ago when I had to have the intake manifold gasket and bolts replaced. Apparently they didn't get it quite right when they reinstalled it.

Anyway they are not absolutely sure this was the problem, but they are sure it is one of them. I am going to drive it a while to see if I get any more codes, and this time I will check but not delete them. I'm not sure, and neither are they, why this would affect only one bank of cylinders.

There was no charge from the shop for diagnosing and retiming the distributor.

 

ok coildrive is causeing the fuel trim to change which is causing the 12.. code. this is going to cause the mis fire being as the pcm is trying to retard or advance some comp for the extreme fuel curve change caused by the MSD system. unplug all after market tuners and run her 30 miles the light should shut off and then your good to go. if not the you probable have a hard fault. as for the vacume lines get or do a smoke test we find its mostly vent valves get **** in them and dont close fully. dont waist time changing all the vacume lines you will just get annoyed and pissed off trust mine. mine actually got removed because of it.