Very slow and sputtery 99 2.5

[Yourt16]

Hey everyone I have a 99 ford ranger 2.5L. I was driving the other day and it felt like it was taking forever to get to 55. I slowed down and it started shaking. I pulled the codes and got p0303 and an upstream 02 sensor code. I also had a p0171 but I cleared it and it didn't come back. I changed the fuel pump, egr valve, plugs and wires, had the cat tested, and the fuel filter. Any help would be greatly appreciated!!

 

[Marty'70]

Have you ever changed the timing belt? Possibly stretched but not broke yet letting timing off a little.

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[Yourt16]

Have you ever changed the timing belt? Possibly stretched but not broke yet letting timing off a little.

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Yep changed it 10,000 miles ago

 

[adsm08]

From the list of stuff you did replace it sounds like you ignored 2 of the 3 items on the ignition side, one of which being the most common cause for a misfire, the spark plug.

A dead miss can cause a lean code because an O2 (oxygen) sensor only see, wait for it.... OXYGEN.

A misfire puts lots of fuel and oxygen into the exhaust because nothing is burning. Since it isn't a fuel and oxygen sensor, just and oxygen sensor it can't tell the difference, an BAM, your misfire sets a lean code.

 

[Yourt16]

From the list of stuff you did replace it sounds like you ignored 2 of the 3 items on the ignition side, one of which being the most common cause for a misfire, the spark plug.

A dead miss can cause a lean code because an O2 (oxygen) sensor only see, wait for it.... OXYGEN.

A misfire puts lots of fuel and oxygen into the exhaust because nothing is burning. Since it isn't a fuel and oxygen sensor, just and oxygen sensor it can't tell the difference, an BAM, your misfire sets a lean code.

I said I replaced the plugs and wires, all 8

 

[adsm08]

Ok, yeah, I see where it says plugs. I missed that last night. It could still be a coil.