2005 F150 runs rough, back fires a little, has gasoline smell coming from exhaust and has lack of power sometimes. The check engine light flashes or stays on. I hooked up an code reader and got the following codes: P0306 P0175 P0300 P0305 P0307 P2198 P0308

Sound like it could be quite a few things. Off the top of my head I would check that the car is firing on all cylinders. If one has gone down you will have fuel travelling along the exhaust pipe, which could explain the smell. If you have lost a cylinder it will be as rough as a badgers B*M, and you will get rubbish mpg. Check if you can smell fuel from the exhaust pipe (Not while the car is running I don't want you to get carbon monoxide poisoning), just give it a quick start and a few revs first. If it is or anyway If you take the plugs out one at a time look at them to see if they are wet and smell of fuel, (After a quick start and a rev). Check your air filter as well you could even take it out and see how it runs (Not for long just a quick blast) see how you go with that.
Good Luck

Flashing MIL Lamp on a Ford, is a Class A exhaust
converter damaging Cylinder Misfire

Get your codes ,google them & diagnose the problem
& don't use it until resolved

Hi Marlene:
When the light comes on, one or more diagnostic trouble codes (DTC) are stored in the engine control module. These DTCs remain even if the light goes out. To address a Check Engine Light problem, the DTCs are retrieved and the appropriate troubleshooting information is followed in order to determine the problem.

The Four Most Common Check Engine Light Scenarios and What to Do:
* The Check Engine Light turns on and off or flickers.
If the Check Engine Light comes on in the city but goes off on the freeway, then the fault is present during city driving conditions. Pay attention to whether or not the vehicle runs or drives any differently when the Check Engine Light illuminates. If vehicle performance does change, drive the car as little as possible and take it to be checked by a service professional as soon as possible. If there is no change in vehicle performance, you can drive home, but have it inspected as soon as possible. In this condition, you run a risk of the vehicle dying or not starting.

* The Check Engine Light comes on and stays on.
If the Check Engine Light illuminates constantly during driving with no noticeable driving or performance problems, there is a permanent fault in the emission control system. When this happens, the computer that controls the emission system usually has a backup program that runs while the fault is present. (These backup programs are often referred to as "limp home" mode programs.) You should get the vehicle serviced as soon as possible, but in most cases, the vehicle will continue to operate, though you run a risk of it dying or not starting.

* The Check Engine Light illuminates, stays on, and there are performance problems.
This means that a vital component of your emission control and engine management system has a serious problem. It usually involves a component or system needed for the vehicle to run at all. In most cases, drive the vehicle as little as possible. In many cases, the vehicle is not safe to drive at all -it could stop or stall out at any moment. It is best to pull over to a safe place and have the vehicle towed to an automotive diagnostician for a thorough inspection and repair.

* The Check Engine Light light comes on and blinks in a steady pattern while driving.
Don't confuse this steady pulsing of the Check Engine Light light (usually one or more flashes per second) with a flicker (see above). The Check Engine Light may stay on steadily or it may flash when the vehicle is accelerated. This is very serious. There is a severe failure of the emission control system that is causing the engine to misfire to the point that the catalytic converter is damaged each time the Check Engine Light flashes. It may mean that the catalytic converter is overheating to the point that it will glow red or, in extreme cases, start a fire on the underside of the vehicle. Immediately pull over to a safe place and have your vehicle towed to an automotive diagnostician for repair. Vehicles can be severely damaged and even destroyed by fire if this condition is ignored for too long.

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It called lack of back pressure in your exhaust system. The newer engines today are made to have certain back pressure to operate properly.As a general rule, you can enlarge the pipe diameter of your OEM exhaust system by 1/4- to 1/2-inch to increase your horsepower. However, any additional increase in pipe diameter is likely to decrease your performance; specifically, low end torque. You can fix this problem if you can find a speed shop to dyno-tune your F150 with the lower back pressure exhaust system you have buy changing your fuel injector timing and pulse duration. Good luck and keep me posted, your engine may running to lean at the higher RPM's so be careful not to burn out one of more of your valves. Thank you for using Fixya.

have vehicle scanned for the trouble code some thing is going and the code will give u ur starting point most auto stores will scan for free such as auto zone / advanced auto --if it smells like rotten eggs or like sulfur most likely catalytic converter going

check under hood while it is running to see if there is gasoline dripping anywhere. You need to find it before it catches on fire. Use a bright flashlight and look at the fuel injectors and loser intake manifold as injector o-ring could be leaking. DO NOT use a lighter. Sorry, but I had to stress this. Gasoline does not burn. The fumes burn.

Typical symptoms of a blown headgasket may include: -bubbles of air coming up into your radiator (remove cap before starting) -leaking radiator -milkshake colored oil -overheating -rough running -coolant or oil running from head -spark plug(s) that have a green tint (if green coolant). -white colored or sweet smelling exhaust, white smoke of your tail pipe, or loosing coolant through your overflow

if the exhaust blows black when this issue starts,then probably a bad regulator,which the check engine light will come on then go off a few times telling you a code,oxygen sensors...if not,try replacing the throttle position sensor,its tough because its at the bottom of the throttle body,and the screws rust in and sometimes breaks,so the throttle body has to come off.you have to figure out where the gas smell is coming from at least,it could be blowing back into the air breather.also check the vacumn lines(green hose and red hose) on top for cracks.the red should be for the regulator

the cat converter is overheating because the engine is misfiring, get it to a repair shop ASAP, I would tow it, but converter damage has already been done.

did you put the platinum plugs back in.get a noid light test the injector wires make sure they are working . when you hook noid light up these should have a steady blink .if light dont blink just light up.you got pcm problems .if you get no lights you have open wire.besure to check ignition coils that control those misfiring cylinders.