Have original spark plugs in my 2009 Taurus with 129000 miles. Car runs good, gas mileage good. Should they be changed?

Runs good. Gas mileage okay. Should they be changed? Approximately what's an average charge to change plugs?

– Have original spark plugs in my 2009 Taurus with 129000 miles. Car runs good, gas mileage good. Should they be changed?

Car rev’s fluctuate when idling sometimes, happened twice in one week.

Twice this week (once while stopped in my garage and once at a red light) the rpm's on my car started to go up and down while I was idling. They would go so low that I thought my car would stall out.
The first time was in the garage. I turned my car off and then on again and it seemed to have 'fixed' the problem. When at the red light, once I started driving again, that seemed to 'fix' the problem.
What do you think may be causing this being that it's so infrequent.

My car has 209000 miles.
My car has an automatic transmission.

– Car rev’s fluctuate when idling sometimes, happened twice in one week.

TPS connector voltage

I've come a LONG ways with this car. Hopefully this will be my question. On my TPS connector I'm suppose to be getting 5 volts on my voltage signal wire, .9 to 1 volt on my signal wire and .30 ohms on my ground wire. My voltage wire is getting the proper 5 volts. My ground wire is getting the .30 ohms. But my signal wire that's suppose to put out .9 to 1 volt. But it is putting out 4.56 volts. That's about the same as my voltage wire. What would the problem be and what's causing this. HOPEFULLY it's not my computer on the car. Is this something that I need to trace the

– TPS connector voltage

Codes po171, po174, po303, po741

I recently had my car tested and it showed the codes above. My service light is on but sturdy. I have lack of lpower and a rough idle. When I stop my car vibrates with surging on the acceleration. Prior to all of this I had spark plugs replaced and the light was still on. I was told that po352 was misfiring and had a front ignition coil replaced. I am still have problems. My car has been running great. I keep maintenance on my car but all this is new and I am a female, veteran as well as a senior citizen this is the only transportation I have and I want my car running smooth again. Please prov

– Codes po171, po174, po303, po741

have a 98′ Honda Civic Dx with manual transmission that’s got some sort of issue. Most of the time it runs just fine, but randoml

I have a 98' Honda Civic Dx with manual transmission that's got some sort of issue. Most of the time it runs just fine, but randomly it will start to idle rough. When it does this it will also sometimes sputter out and die, specifically in 1st or 2nd gear, once I begin to give it gas and accelerate from a dead stop.. It it will go from running great to idling rough and sputtering at random moments, intermittently. It has no check engine light. What could be the cause of this? It has a new fuel pump, fuel filter, spark wires, and a new air filter.. any ideas on what could create this p

– have a 98′ Honda Civic Dx with manual transmission that’s got some sort of issue. Most of the time it runs just fine, but randoml