How to repair nissan serena 2002 model qr20 engine rougth idle

Things to check
Plugs;
Remove the spark plugs and read them, they should all have a dry tip and be clean from any carbon, oil or fuel.
Usually if burning fuel properly they will have a brown or whitish looking tint from burned carbon.

If any of the plugs look wet or black or dirty looking different from the others the problem is with that cylinder, change all the plugs and see if that helps, the next lease expensive thing is replacing the plug wires.If your fouling plugs ask your parts store for 1 number hotter plug ( heat range)

Plug Wires;
Open the hood at night with the engine running and see if you find any blue looking arcing around or in the wires, if so replace the wires.

Fuel Injectors
If all above looks good your fuel injectors might be dirty or one might not be working. You could try an injector cleaner mixed in with your gas

A rough idle comes from one or more cylinders not firing as hard as the others or not at all, there are so many causes for this so you have to troubleshoot with the lease expensive fix first.

Another thing is water in the gas, you can pour plain ole rubbing alcohol in your gas tank if you suspect water in your gas. alcohol mixes with the water and makes it burn instead of mis firing.

Valves
One more thing that can cause rough idle is your valves, this requires a compression check on each cylinder. If one cylinder has less compression than the rest remove the compression tester and squirt some engine oil in the cylinder then re test, if the compression increases it is bad rings or a bad cylinder bore, if not it is a valve problem.

Oil seals around the piston increasing the compression temporarily while testing but makes no difference in testing if the valves are leaking.

Good Luck,... troubleshooting and patience, or a good mechanic is the solution if you are working with neither

Hola rengonun Nissan Serena 2002 motor QR20 tengo el siguiente porblema, no llega corriente a la bomba de combustible, Ya revis? fusibles y relevadores todo estan bien. Da arranque pero no enciende el motor. GRACIAS

I have Nissan Serena Model 2003 A/T, the engine is very good, when it start & running you can bearly hear the engine is running. One day I drove it and stopped to take my lunch, after that nice lunch, the car wont start anymore?
Trouble Shooting made:
Step 1: Turn on the key to let the fuel pump work and push the supply of fuel to the injection system. then try to start. if still not start go to another step.
Step 2: Make sure to inspect all the wires of your plugs, if everything are OK, remove the plugs (4 of them) then connect to your plug wires, start the engine make sure there are electric going out from your plugs, if that so, then all the wires and plugs are OK, restore the plugs and wires to normal condition. go to another step.
Step 3: Unplug the fuel hose connected to your fuel injection system, and get one empty plastic bottle and insert the the unplug hose to the bottle, start the engine to see if there is fuel going out from the hose, if none, restore the hose to original location. (next step).
Step 4: Switch on your key (not to starting), then try to feel by you hand the fuel pump located at the back of driver seat where the fuel tank is located, feel if there is vibration, an indication that the fuel pump is working. If no vibration or sound of working fuel pump, go to another step.
Step: 5 Locate the fues box under the dashboard front of driver seat and locate the fuse assigned to the fuel pump, check if busted or not, if busted replace then start your engine. If everything OK then you solved the problem. (If not start go to the next step).
Step: 6 Remove the cover of the fuel pump located on top of your fuel tank, unplug the power plug connecting to fuel pump motor, unplug 2 fuel hose from the fuel pump, slowly remove the fuel pump from the tank. Access the small submersible pump and test it by directly connecting to 12VDC (Test it away from the tank to avoid any spark from the wire connection from the terminals of submersible pump). If pump does not work replace it and restore back all the assembly related to fuel pump. Turn on the key on ON position (not Staring position) to give ample time to pump fuel and distribute to the fuel injection system (duration 3 to 10 seconds), then start the engine.

These are my experience in trouble shooting my Nissan Serena, till now it is working fine.