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Scottdagoalie, Senior Master Tech.
Category: Ford
Satisfied Customers: 1940
Experience:  30 years with Ford dealers
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I am getting two codes PO 304 and PO 316. 304 is misfire

Customer Question

I am getting two codes: PO 304 and PO 316. 304 is misfire on Cylinder 4 and 316 is misfire first 1000 revs. I have changed the plugs, wires, injectors, vehicle speed sensor, Idle Air Control Valve, fuel filter, and coil pack amongst other things. Anyone have any ideas what the problem might be?
Submitted: 8 years ago.
Category: Ford
Expert:  Scottdagoalie replied 8 years ago.
HiCustomer Thank you for asking your question on JustAnswer. The other Experts and I are working on your answer. By the way, it would help us to know:
-What year is your Ford?
-What model is your Ford?
-How many miles are on your Ford?
-What type of engine is in your Ford?
-What have you already tried?

Thank you again for trusting us with your problem. Please reply as soon as possible so that we can finish answering your question.
Customer: replied 8 years ago.
Hi Scott. Sorry about not including the pertinent info. Its a 2004 Ford Ranger 3.0 V6 with 86,000 miles on it. The code says misfire on cylinder 4 and it has a miss but I have changed the plugs, wires, coil pack, injectors, vehicle speed sensor, the idle air control valve, and done a compression check. The cylinder is not low on compression. My dad (a master mechanic for 20 years at the city of fort worth) just finished checking the injector wires and said that they were ok. This has me pretty well stumped at this point.
Expert:  Scottdagoalie replied 8 years ago.
WellCustomer I've found that when you've checked everything that can cause a misfire and find nothing wrong,check again. Occasionally the plug gap can close up if tweaked during installation.Recheck the injector pulse signal to the injector,sometimes you can plug an adjacent injector plug onto tthe suspect injector to rule out a signal problem. I have seen PCM's fail and loose injector pulse signal to injector under load. If you have a scan tool with data monitoring you can watch the individual injector. Swap plug wires around to see if you may have a defective one. Hope this information helps.