Misfire!

[mach007]

The SES light came on 3 days ago. Looked up the code and it was cylinder 5 misfire. The vehicle emits a "put put put" sound ONLY at idle, but runs strong at freeway speeds. The code disappeared twice today, but returned shortly after. I took it in to get a diagnostic and this is what they said:

"Customer request cylinder misfire. Diagnosed cylinder misfire. Retrieve DTC's from computer. Code P0305 present,cylinder 5 misfire detected. Code P0316 present, detection misfire on start up. Checked fuel pressure. Fuel pressure in specification at 51 P.S.I. Listened to fuel injectors for noise patterns. Injectors sound good. Spark plugs and coils are brand new and in working condition. Performed vacuum test. Found that at 18 P.S.I in drive there's a fluctuation. Problem happens at low RPM's. Issue at hand is a mechanical problem. Possible burnt or sticking valve. Recommend trying fuel injection service and chemical/additives first. Use Top Tier gasoline only with additives"


Current mods on the car: JLT RAI, UD pulleys, and chambered design mufflers. The vehicle runs on 5w-20 Mobil 1 synthetic oil with a Mobil 1 oil filter. Car has 80k miles, it's an automatic that is used 2 times a week for 74 miles a day.

My question is what can be done to stop it from sticking? Or worst case scenario, what am i looking at to replace a burnt valve?


Thanks and please help. I would appreciate it.