Nissan Repair: 03 Maxima rough idle &starting problems, vent hoses, loose hose

Question
My 03 Maxima (193,000km) has had a rough idle and often has to turn over for a long time before it starts. Above idle all seems fine and fuel economy is OK. The car failed it's emission test, idle emissions were way out of spec. I just got a code reader and the following codes are in P0300 P0455 P1448 P0132 P0300. I changed the 4 easy plugs which made no difference and the plugs I took out didn't look too bad.

The problem is often intermittent, and doesn't seem to be hot/cold dependent.

The engine monitor I got yesterday lets me see certain perameters as you drive. I haven't had time to do much, but it did seem that the ignition timing was at 9 degrees when the idling was rough. A bit of gas and the timing went up a bit and things smoothed out. On the highway, it was 32 or so (if I remember right).

I had a mechanic look at things a couple of months ago, and it seems like the fuel pressure might not be staying up all the time (after engine shutdown if I remembered right).

I'd appreciate any insight. I haven't driven the car since Christmas (when it failed the Etest). It's back on the road for a few days right now with a temporary permit.

Thanks in advance.

Answer
Andrew,

A couple of things here.  First, change all the plugs and use NGK or Nippondenso.  Do not use Bosch.  Second, replace the coils.  The codes you are getting are for random misfire and the other is for the evaporative system.  Nissan had some problems wiht rotting fuel vent hoses.  You could check the hoses and the evaporative canister under the car, driver's side, at the back bumper.  Also, make darn sure the gas cap is ok.  The coil problem is a known one from 1999 on up to 2003 and the vapor lines for the closed fuel system are known too.  It could be as simple as a loose gas cap or a damaged fuel line or even a loose hose clamp.  courtesyparts.com is a good source for original Nissan parts way below dealer price.  rockauto.com is another.  Checker or Autozone will check and clear the codes for free.  But, you can also disconnect the battery for five minutes to do the same thing with clearing the codes.