2000 civic 1.6. Multiple misfire, random missfire, misfire in clyinders 3 and 4. I know its running lean. I'm thinkin fuel pump, no easy way to check pressure, no nipple and fitted lines. Any ideas?

Hi there:
A code P0300 may mean that one or more of the following has happened: Faulty spark plugs or wires Faulty coil (pack)Faulty oxygen sensor(s)Faulty fuel injector(s)Burned exhaust valveFaulty catalytic converter(s)Stuck/blocked EGR valve / passagesFaulty camshaft position sensorDefective computer
Possible Solutions: If there are no symptoms, the simplest thing to do is to reset the code and see if it comes back. If there are symptoms such as the engine is stumbling or hesitating, check all wiring and connectors that lead to the cylinders (i.e. spark plugs). Depending on how long the ignition components have been in the car, it may be a good idea to replace them as part of your regular maintenance schedule. I would suggest spark plugs, spark plug wires, distributor cap, and rotor (if applicable). Otherwise, check the coils (a.k.a. coil packs). In some cases, the catalytic converter has gone bad.
If you smell rotten eggs in the exhaust, your cat converter needs to be replaced. I've also heard in other cases the problems were faulty fuel injectors. Random misfires that jump around from one cylinder to another (read: P030x codes) also will set a P0300 code. The underlying cause is often a lean fuel condition, which may be due to a vacuum leak in the intake manifold or unmetered air getting past the airflow sensor, or an EGR valve that is stuck open.
Hope this helps.

Well for starters fuel pumps are electric and 99 percent of the time if they are bad they just do not work so I doubt the fuel pump is the problem. If you are sure you are getting a misfire your computer should pull a code and tell you this. If this is the case I would start with the basics. Check your spark plug wires by checking the reistance on them with a digital ohm meter. If the resistance is above 25kOhms that wire is bad. You can also check the injectors. Not sure of the reisitance on those but if you check each one and one is way different then the others then that means a bad injector which will cause a misfire. If all looks good there, the next step would be to make sure you are getting proper spark at each wire & plug. Finally if you have a fuel problem you can check for proper voltage at the injectors. You should have power at all time at the yellow and black wires on each of the injectors. Your computer sends a negative or ground "pulse" which is what comepletes the circuit and opens and closes the injector. Since you say it's either cylinder 3 or 4, check when the engine is running to see if you are getting a good and even negative "pulse". The blue wire is the negative pulse for cylinder 3 and the yellow is the one for cylinder 4. Start there and narrow down the source. As I said, I think you would be wasting your time dealing with the fuel pump for right now.

I would back it to honda dealer for a second opinion but its one of a couple of things here and first check the plugs for a 25 th gap ,then see what happens as iam not familar with this engine so does it have a coil pack or a coil on each cylinder but either way it could be a crank sensor a cam sensor if fitted or worse case scenario a ECU but to diagnose correctly you will need the dealer software to measure the voltages and the fuel flow from the sensors and the pulse to the injectors ,i know it can be done with a automotive multimeter to an extent but to know what the ECU is computing and adjusting to suit is difficult with my meter and i have been coming across a lot of vehicles with this sort of problem from the ECU even more so since they are made in china mostly and standard of the components is a well not very good as far as iam concerned so do wast money on what you think may be wrong have it checked out