Hi there! I have a po-304 code keeps coming up on my scanner. The 1997 explorer 5.0L has a dead miss and it stinks of unburnt fuel? I have changed the the #4 spark plug and the coil pack, the plug wires are fairly new. It still runs the same? This came on rather suddenly also. Thanks for your time!

Code 304 is for a miss on cylinder 4. Could be a spark plug or fuel injector issue.

having PO 304 = Misfire cylinder 4,PO 306 = Misfire cylinder 6, as I read above you have done the most. The thing that you have missed is to check whether the Catalytic Converter is faulty or not. To get an idea check whether you have a smell like rotten eggs at the end of the exhaust,you start having problems with cat and needs replacement. My advice before you go for a cat replacement is good to visit an MOT center and check your emissions and then you decide,

this code indicates a missfire problem on cylinder #4,,this could be a bad plug,wire,injector,igntion module for cylinder 4,compression problems.that need to be checked out.

hi p -codes are as follows po 301 cylinder 1 missfire detected
po 304 cylinder 4 missfire detected
po 335 crankshaft position sensor A circuit malfunctio
po 750 shift solenoid A malfunction

What codes do you get? Is the check light on steady? Did you switch coils to see if code PO 304 & 2 move. What does fuel pressure look like? Are the O2 sensors in tight and have you looked over the entire PCM System with a professional scanner? How were the injectors and coils checked?

ck if you have spark at the coil for that cylinder. check the plug wire closely. if it has spark at the coil, then replace all the spark plug wires.

P0304 is Cylinder 4-misfire detected-probable cause is as follows. Engine mechanical fault, wiring, ignition/fuel system, injector, ECT/MAF sensor, ECM

P0316 Misfire detected during startup-first 1000 revolutions- probable cause is as follows-Engine mechanical fault, wiring, ignition/fuel system, injector

Information courtesy of http://obd-codes.com

A code P0304 may mean that one or more of the following has happened:

• Faulty spark plug or wire
• Faulty coil (pack)
• Faulty oxygen sensor (s)
• Faulty fuel injector
• Burned exhaust valve
• Faulty catalytic converter(s)
• Running out of fuel
• Poor compression
• Defective 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.

Hope this helps with your problem. Best of luck.
Greg

Possible causes
- Missing Fuel cap
- Incorrect fuel filler cap used
- Fuel filler cap remains open or fails to close
- Foreign matter caught in fuel filler cap
- Incorrect fuel tank vacuum relief valve

hi changing glow plugs is nothing to do with this code i would change the fuel filter and put a injector cleaner into the fuel tank as if this doesn,t cure the problem the only other thing that affects the pump is the timming belt has it slipped a tooth is there a marked drop in preformance if not these pumps are expensive very expensive best of luck yates210456