Hi, I am a new member, and sure would appreciate help with this code. I have a 2001 Taurus OHV 3.0 engine and have already changed the coil pack, the spark plugs, and the plug wires. The car keeps running rough, and also knocks only upon "acceleration". I am at a loss as to what's next to do. Does anyone have information that can help me? Thanks very much!

 

It would be a good idea to check out the EGR system.
Did you have the miss in the #4 cylinder before or after you changed the plugs etc. ?

 

Hi, thanks for responding. Actually, this code has come up several times. I had already chaned the plugs, and wires when the code first came up( that was a few months ago). Then the car seemed alright, but started jerking, running rough and through the PO304 code again. Recently, I installed a new coil and it ran ok for awhile. Now it's back showing PO304 again. You're right, I should be addressing the EGR and I put some lubricant on the bolts, but they won't budge. Frozen on there I guess. But I'll keep trying Thanks

 

A few other thougts on this from someone who did way too much work on these. First, if the engine misses; is there a spark present at the coil? Many of these would short out one tower of the coil pack and the twin tower would still run perfectly. Also, if it misses more when cold and not so much hot, then suspect a fuel injector. I've had to replace a few that would not flow enough cold but worked fine hot (though when they get plugged enough, they won't well when hot, either).

 

Hello, how exactly do I check for spark at the coil? I'm not real familiar with that. Also this is a brand new coil, would that still be a problem? Actually, this code came up before with old coil as well. It really just knocks and hesitates upon acceleration, and then smooths out. If I keep it under 40 mph, it does fine. What do you think?

 

It's unusual for the same problem (misfire #4 cyl) to disappear for a short while after replacing a coil pack only to come back again. I know you are trying to help yourself, but in a case like this it might be a good idea to have someone with the right test equipment to check out the entire ignition system from crank sensor through ignition module , cam synchronizer etc. As greasemark stated you could also have a questionable injector. The question is why does it go away after you replace the coil pack only to come back again later. Possibly a lean mixture in that cyl is temporarily overcome with the higher voltage from a new coil, don't know.

 

I know, I thought I had it solved because I believed it was in the ignition systemThanks. I will clean out the EGR and look into the injector problem as well as have someone test compression. Thanks again!