Nissan Repair: 1995 Maxima miss/skip problem., fuel pressure gauge, coolant temp

Question
QUESTION: Bought my son a 95 Maxima with approx 160,000 miles on it. Had a slight skip/miss at idle while under a load, in drive with foot on the brake. Replaced plugs with Champion and it ran well for a few weeks then started an awful miss/skip. I put old plugs back in and it ran fine for a week or so. Problem resurfaced with a CEL light. Car is not OBDII and local shops couldn't pull codes, need the Nissan adapter. So I pay the dealer to pull codes and there are three,
1. Coolant Temp sensor
2. Knock Sensor.
3. Ignition Primary
I replaced both sensors and all six coil packs and put in 6 new PFRG5-11 factory plugs gapped correctly. This $%*@% misfire is still present, I'm about to blow an gasket myself!!
Problem is imperceptible at higher rpm's and accelaration and cruise are normal or appear to be.
Also I can smell what seems to be raw gas when he pulls into the driveway, could this be connected to the problem? Is this gas smell a known Maxima issue on older cars? Can't tell exactly where it's coming from.
Thanks in advance for the help guys.
Mark.

ANSWER: Mark,

Sounds like you have a bad injector or two.  I would do a fuel pressure test and see if any are leaking and also perform an ohms check on each injector.

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QUESTION: I think the Nissan Dealer did an ohms test, how do I conduct a fuel pressure test?
Thanks in advance,
Mark.

Answer
Mark,

Get a fuel pressure gauge from the parts store.  Some stores will rent them and you can purchase one for about $40 bucks.  It screws onto the fuel rail like a valve stem cap on a tire.  Once it is screwed on, wear glasses so you do not get sprayed with fuel, start the car and note the fuel pressure.  While looking at the fuel pressure have someone turn the engine off.  If the pressure drops suddenly you have leaky injectors.  If the pressure stays up for about a minute you have tight injectors.