p0304 mystery code

99 wagon DOHC

I had this code and tried a new coil, new plugs, and wires. Then I noticed the vacuum line that runs from the TB to the passenger side of engine(connects to some kind of switch), then back to the EGR was cracked right at the TB. So if you are getting the shudders and crazy acting engine check this hard vacuum line.

Welcome to the Forum!

Thank you dingodingodango. You'd think they would come up with a rubber compound that wouldn't deteriorate for vacuum lines, but you've got to hand it to the manufacturers. It's a great way to get people back to the dealership for that minimum of 1 hour labor.

Hi...just acquired a 97 Ford Taurus GL...99,000 miles. First time driving ,no problem, smooth as silk.Get the car home, get tags, etc etc..Next day go to the store, after approx 4-5 miles check eng Lt comes on, check codes ...P0304, misfire on cylinder 4.Ok...no problem, check wires, were original , changed, changed plugs, runs smoother, again after same distance, light on again, same code ( code cleared previously). Checked all hoses, coil pack resistance ok, --so checked injectors, all but one were working, so now I have a fuel injector to replace..anyway, does anyone out here know where to go with this next? Had the car 2 weeks and afraid to drive it. It's in great shape body and interior...so a little bit of pampering is ok.......any ideas on what the actual problem is? Thanks in advance!

So is the fuel injector that is not working the cylinder #4 injector? On your Taurus, cylinder #4 would be the cylinder closest to the belts on the bank of cylinders just behind the radiator. A fuel injector that is not working could explain a misfire, but you'll want to confirm the injector is the problem rather than the wiring and signal to it.

-Rod

Thanks for responding...yes it is cylinder #4... today after idling the engine about 5-10 minutes, the check engine light came on again, took the stethoscope and put on each injector, 6 ..clicking..5 ...clicking etc. Placed on #4 ...no sound. So he unplugged the #4 injector, put the noid light in the socket, the noid light flashed letting us know the voltage was there.Then he checked the resistance on the injectors, all were between 13 and 15 ohms. When he checked #4 the resistance was 200 ohms. This is the next plan , just hoping for a good day in between the snow ! Car has 99,000 miles, very nice shape, but not being able to drive it is driving me nuts �� Any further info would be greatly appreciated...are we on the right track? Thanks Rod

I certainly think you're on the right track. If the noid light flashes, you should have enough current to drive a good fuel injector. I'm comfortable that replacing that bad fuel injector will take care of your misfire. So far you've performed good diagnostic work.

-Rod

I certainly think you're on the right track. If the noid light flashes, you should have enough current to drive a good fuel injector. I'm comfortable that replacing that bad fuel injector will take care of your misfire. So far you've performed good diagnostic work.

-Rod

Hi Rod....it's been awhile since my last post, after winter we finally got the chance to work on the Taurus...we did replace #4 injector, also while we were in there replaced the leaky water pump....slow leak.Anyway...just wanted to let you know that the injector was the problem...a pain to fix but drives like new! Thanks again!

Awesome, thank you for following up with what you found!

-Rod