98 sport trouble starting

I just purchased a 98 explorer sport two weeks ago - it was running great but now i have a hard time starting it like in the morning and after it rests for a while, it still runs great and when i'm driving up hill it sorta chokes.
i had a fuel filter changed couple days ago and it still does it and we had it sent to a diagnostics and they said nothing wrong with fuel pump.
anybody know what could be?

I just changed the plugs also but i have a problem with getting the plug off from the passenger side.
Anybody know how to get this one? It's way inside where i can barely get a finger on it.

Thanks

I have a 98 Merc Mountaineer/Explorer. I could not get to that plug either. Inside the right front fender wall there should be flap you can bend up to get at the plug with a universal joint and plug socket. Just be patient it was difficult, but I got it. I used this route for both plugs.

I just purchased a 98 explorer sport two weeks ago - it was running great but now i have a hard time starting it like in the morning and after it rests for a while, it still runs great and when i'm driving up hill it sorta chokes.
i had a fuel filter changed couple days ago and it still does it and we had it sent to a diagnostics and they said nothing wrong with fuel pump.
anybody know what could be?

You can remove that flap - those are plastic push pins holding it in. Easy plug access.

Examine your plugs carefully.

I had a 99 that was a tough starter after sitting awhile. It was a leaky fuel injector. The plug for that cylinder had a lot of deposits on it, and after sitting overnite, I could smell gas on the plug.

Leaky injectors will not set any kind of code.

98 Merc Mountaineer- Just replaced the IAC motor and took a 3.5 hour trip the Port Aransas. The truck had problems starting the whole week end. The guys at Napa auto parts suggested I depress the excelerator in about a quarter of the way when the problem occurred. I tried it and it seemed to start on the second try when I did that. It also seem to start on the second attempt when I started from the off position. Not sure what to think now. I've replaced the coil as well as the IAC. I wonder if it is a falty temp sensor.