How to Diagnose a possible injector problem on a 2003 xterra 3.3 engine

run the fault codes to look for injector problems
check injectors for bad tips
check fuel pressure to injectors
check for vacuum leaks with the foot on the brake ( booster leaks --check by applying the hand brake with the foot off the brake and if the problem is not there it is the brake booster faulty)

You need a volt/ohm meter to check the injectors. The injector should ohm out between 11 and 15 ohms(leads on both ends of the injector). Set the meter to the lowest ohm reading. On the plug end you should have a jumping reading, when cranking the engine, set it to dc volts.. It never gets to 0 volts or 12 volts, Just jumps between them. If you have no voltage from the plug end, then the wire is broke. Usually by the plug. Set it back to ohms and check the plug and pierce the wire about 3 inches back. See if you get a reading. Should be close to 0 or .05 ohms. If not, fix the wire. You may have to go further down on the wire. You can get a cheap ($20) meter at any parts store.

Its possible the miss is still there in park but not as noticeable. The problem is worse in drive because of the load on the engine.
It could be one injector that has worn out, the magnet that opens the injector valve can get weak. It could be gummed up and the cleaner may help, but you may have to replace one of the injectors at the end.

engine shake could be misfiring or even a broken engine mount. Not related to your battery.

The P0304 indicates the #4 cylinder is misfiring. The flashing light means the cylinder is not firing at all...It could be several things causeing it, coil, wires, plug, injector or vacuum leak. Do not drive your vehicle until you have this repaired, as it will lead to further more costly problems. Good luck, i hope this helps.

it is not likely to be a fuel issue ... more likely it is your spark plugs or spark plug wiring. If one of your plugs is not firing right, then that piston will not function normally and cause a violent shake in the engine. This will be more noticeable when accelerating as more fuel is pumped into the piston and is not being burned off properly. This could cause the strong smell of exhaust, as the flow of the exhaust would not be normal.
It is also possible that your timing chain has skipped a tooth, causing a misfire in your engine -- this could also cause the exhaust flow to be abnormal, giving a strong smell of exhaust when the issue occurs.
Another possibility is that you have a bad fuel injector on one of your pistons ... but this is more likely to make your engine sluggish than cause it to shake violently -- usually a bad injector does not shoot enough gas into the piston, rather than pushing too much.
There is also the possibility that you have an issue with your exhaust manifold (though this is less likely and would probably make your vehicle very loud) -- if there is a hole in the exhaust that would cause the strong smell ... and the improper back pressure could cause your engine to work badly. Once again, this is unlikely to cause a violent shake in your engine ... but it is possible, so I mentioned it.
I would first check the spark plugs, then their wiring as these are the cheapest and easiest repairs that could resolve the issue. If neither of these is the problem, check to see if your car is reporting a problem code (under the passenger side of the dash there would be a blinking light -- count the number of blinks and use that number to reference an error code). If your engine is reporting an error code, that should help you diagnose the issue. If the plugs are not the problem, and the engine is not reporting an error code, I recommend taking the vehicle in to a mechanic. A professional with the vehicle in front of them will be able to provide you with a better diagnosis.

I use to have a 1991 Nissan Pathfinder XE with the 3.0 engine automatic transmission. It ran fine when I baught it then started having hard to crank or dieing going down the road syndrome. Very simular to your problem. I had a Nissan technician friend in Tennessee and he told me that the distributor goes bad it will behave that way. Usually the problem can start off slow like mine where it would hard to start and die or just go completely out. I recommend replacing the distributor. Mark the shaft alignment before removing the old one and install the new one aligned up the same as the old one was. Just an added tip the 3.0 Litre engine block is the same as the 3.3 litre engine and theres alot of guys dropping these 3.3 engines in the old 1980 model 300Z cars! I own a 2001 Xterra so feel free to ask anything! Harlan or [email protected]

codem p 0203 refers to injector 3---circuit malfunction===causes wiring--injector--ECM
chweck for harness connection , bad wire for no 3 injector or corroded pins for no 3 injector in the connection

SOUND LIKE SEVERE ENGINE MISFIRE HAVE VAN SCANNED AUTO ZONE WILL DO IT FOR FREE .BUT MAKE SURE FUEL FILTER NOT STOPPED UP MAKE SURE PLUGS AND WIRES IN GOOD SHAPE.FILL FUEL TANK UP.PUT A BOTTLE FUEL INJECTOR CLEAN IN FUEL TANK.TO CLEAN OUT FUEL INJECTORS WHILE YOU DRIVING THE VECHICLE.ALSO BAD COIL OR COILS WILL CAUSE ENGINE TO MISFIRE SHAKE.

try changing out the plugs and test each cylinder.Also fuel injectors could be bad or clogged Im going to give out a little secret for you go to the truck stop big 18wheeler refuel store and buy some diesel fuel cleaner yes diesel fuel cleaner for your gas related clogged injector problem pour in 1/4 for the big bottle and 1 1/3 for the medium sized ones and the entire bottle for small one work with every fill up on gasoline engines no injector or hesitation problems better acceleration and response unlike others who have the 2003 better performance and gas mileage also