One cylinder misfiring. checked injectors and tappet clearance both okay. Suspect poor compression on cylinder number one. Defender 110 tdi

Perhaps there is a wiring fault and the injector isn't receiving a pulse.

Compression check isn't very helpful and a cylinder leakage test would reveal a fault that might cause the misfire - poor intake valve seat for instance.

I once encountered a Ford with a misfire - the compression pressure was ok at starter speed but because the exhaust camshaft lobe had all but disappeared, the misfire was apparent as soon as the engine was started.

p0171 is fuel injection system too lean - bank 1
possible causes
- Intake air leaks - Faulty front heated oxygen sensor - Ignition misfiring - Faulty fuel injectors - Exhaust gas leaks - Incorrect fuel pressure - Lack of fuel - Faulty Mass Air Flow (MAF) sensor - Incorrect Positive Crankcase Ventilation (PCV) hose connection
p0304 is cylinder 4 misfire detected.
possible causes
Faulty spark plug 4 - Clogged or faulty fuel injector 4 - Faulty ignition coil 4 - Fuel injector 4 harness is open or shorted - Fuel injector 4 circuit poor electrical connection - Ignition coil 4 harness is open or shorted - Ignition coil 4 circuit poor electrical connection - Insufficient cylinder 4 compression - Incorrect fuel pressure - Intake air leak
p0305 is same as above but cylinder 5.
p0306 is same as above but cylinder 6.
p0300 is random misfire detected
possible cause
Faulty spark plug (s) - Faulty ignition coil (s) - Clogged or faulty fuel injector (s) - Intake air leak - Fuel injectors harness is open or shorted - Fuel Injectors circuit poor electrical connection - Ignition coils harness is open or shorted - Ignition coils circuit poor electrical connection - Insufficient cylinders compression - Incorrect fuel pressure

Go to www.landroverweb.com , search 300 tdi and download a free workshop manual.

Check these three things in the misfiring cylinder: spark, gas, and compression. One of them is wrong or missing. For spark check the spark plug and wire. Make sure you have spark on the plug wire, a strong blue spark. For gas, the fuel/air mixture may be wrong. Does the fuel injector pulse, putting gas into the cylinder? Possibly you may have a leaking injector or a clogged injector.

If gas and spark seem okay, you need to check compression in the cylinder. Low compression will cause a misfire. If compression is 20 or 25% lower than adjacent cylinders, that could be causing a misfire. For example, say numbers 1 and 3 cylinders had about 150 psi compression. 80% of 150 = 120, so if cylinder 2 is 120psi or less, that could be setting the misfire code. Low compression can be caused by valves not seating well, or bad piston rings, bad head gasket- something in the combustion area of the cylinder is losing compression.

check compression, check valve clearance, check injector for properly working, check for vacuum leak around this cylinder.

bad senser or computer

so missfire detected and cylinder 3 missfire detected.
check to see injector pulse with "noide light" if ok injector is problem
remove fuel rail and injectors look into top of injector for blockage in screen filter in injector if blocked clean out or injector carby places can remove this screen replace it and test injectors and clean or just buy new injectors. make sure to clean out fuel rail and change fuel filter also.
if noide light flashes irratic or not at all wiring issue, check for power on one wire with ignition on 12v other is earthed by ecu when opened to inject fuel. other thing that can cause problem on cylinder is tappet clearance "shims" too tight, could do compression test to see if compression is low on cylinder or a cylinder leakage test to see if valves are leaking. broken valve spring. valves do not hit piston on these engines even if cam belt breaks, they are a "free wheeling" engine

P0304 INFINITI - Number 4 Cylinder Misfire Detected

Possible causes- Faulty spark plug 4
- Faulty ignition coil 4
- Ignition coil 4 harness is open or shorted
- Ignition coil 4 poor electrical connection
- Clogged or faulty fuel injector 4
- Injector 4 harness is open or shorted
- Injector 4 poor electrical connection
- Improper spark plug 4
- Insufficient cylinder 4 compression
- Incorrect fuel pressure
- Intake air leak

You could have a bad spark plug or a bad coil pack for cylinder 1. Or it could be as simple as a poor connection at the coil pack.
Other possibilities are, bad injector or poor compression.

Check for carbon tracking on plug and wire. Looks like a pencil mark. Replace both at the same time