1995 suburu impreza, constant loss of engine power dosent smoke or backfire just has no power i installed a new air filter and fuel filter plugs and wires but did not help

Backfire is a sign you fuel/air mix is wrong. The backfire is the excess fuel burning in the exhaust. Have you got any warning lights on the dash? When was the last time it was last given a major service? A dirty air or fuel filter can cause issues.
Check your Air intake and fuel system. It could be starving the engine of air or supplying too much fuel to the injectors.
It happens at over 55mph because the engine is working hard and fast pulling a lot of fuel through to do it.

Blue smoke = burning oil

-Air filter could be clogged. Or fuel contaminate water.

Mai Lor

could be a plethora of things. start with the cheapest and work towards the more expensive. I would begin with a tune up. new plugs and wires, oil change, and air filter. if you don't get any better performance change the fuel filter. see how it goes from there

possible ignition problem check ignition coil wires and spark plugs

You say you changed your spark plugs. Is it possible you crossed your wires. Check and see. Good Luck Friend.

I Have a 1999 ford f150 4.6 that back fires and is just running really ruff when idling alot of nack fire a sord of like a pulse going on what is my problem?

could need a new air filter or plugs and wires maybe fuel filter just a couple things to look into

so you gave it a tune-up?

possible causes of of loss of power:BAD SPARK PLUGS AND OR WIRES AND OR DISTRIBUTOR CAP.

GASOLINE FILTER PLUGGED THUS CAUSING YOUR ENGINE TO HESITATE. "loosing power"

AMONG OTHERS BUT THESE ARE THE MOST COMMON.

maybe the engine is worn......old engines tend to loose pressure and they start eating the oil, and also start smoking real bad.

this one is another casue of power loss too.

Hi pcjlfc,

I think its a very good idea, to replace the oil filter, fuel filter and air filter when you replace the engine oil.
I will guess that the fuel filter is in need of replacement. It's also an idea for you to check the air filter. To check the air filter, use a very strong light and hold it behind the filter....If you can see the light through the filter material you're safe, if not you need it replaced. The air filter is a very important filter for durable engine life.

If that doesn't work, we'll need to learn more about what happened as a lead up to the problem.

Best regards Johngee10