Vehicle:
2001 Chevy Blazer 6 cylinder 4X4, 220K + miles
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Current Symptoms:

Iddles very rough in park. If you try to accelerate, or take out of park & it dies.
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Current Codes, checked today:

P0300 -Engine Misfire Detected

P0101 -Mass Air Flow Sensor Performance

P0106 -Manifold Absolute Pressure Sensor Performance
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History:

Started having progressively worse issues accelerating & maintaining slow speeds.

Friend suggested it was a clogged CAT problem.

It sit undriven for about a year, then i removed the cat, checked fluids, Filled with fresh premium fuel. Primed the throttle body to get to start. Now started on own, but only idles rough in park.

Amy suggestions are very much appreciated.

 

Seems that it just barely runs in idle. Could be an indicator that it works in open-loop at idle.
Both main engine loading sensors showing problems (MAF and MAP) could be an indicator of an electrical problem.

What I would do:

Clear the faults, then before re-starting: (This to start addressing the fault codes.)

- Give the engine bay a good cleaning.
- Check all the fuses
- Check all cabling to and from the engine for broken wires, scuffed insulation etc. (Including all sensors, temperature, oil press, knock sensors, etc.)
- Check all connectors - take them apart, check for corroded pins, spray with cleaner/contact spray put back together
- Check all vacuum lines ("All lines!") To and from everywhere on the intake manifold. (If able do a vacuum leak check with a vacuum pump, do so.)
- Also check all the vacuum grommets and connectors (sometimes the rubber rots away and/or breaks.)

In addition - kind of a tune-up: (This to eliminate all unknowns outside of the fault codes)

- Check air-filter and element. (Replace if necessary)
- Check the whole induction plumbing (Looseness, blocking, foreign objects, etc.)
- Check all the spark plug wires
- Check or replace all spark plugs (Punch 6 holes into a cardboard box according to the cylinder location and put the old ones there)
- Check all fluids and fluid levels

Fix everything that you find.

Start it up and check the codes. Then work from there.