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Suburban Sputtering Uphill

My 1999 Suburban K1500 is sputtering uphill. Already replaced: fuel filter, air filter, plugs, wires, pcv, distributor. This took care of engine misfire codes. No error codes for the last two months, but it’s a lousy ride uphill on the highway at 20mph. O2 sensors next?

Check fuel pressure. There should be a fitting on the fuel rail…

If the fuel pressure is correct you might also consider the possibility of clogged converters amd this could be caused by age and poor running.

This can be easily checked with a vacuum gauge.