97 4.3 engine misfire

[stetzz05]

im getting a hesitation upon acceleration on my 97 1500 4.3 . it happens under normal acceleration but not when i accelerate hard. recently replaced alternator and problem started after that. getting a p300 code random engine misfire. is this fuel or electrical? any clues?

[maxwedge]

Make sure you have good grounds, check alternator out put, can you feel an actual miss in the engine like a plug or wire?

[stetzz05]

grounds to bat. and block are good getting 14 .12 from alt. yes can feel hesitation not misfire no skip more like fuel cut out

[maxwedge]

You probaly should have it scanned and look for pproper o2 sensor activity, look at fuel trims to see if it is running lean/rich. If it is maf equipeed this could need cleaning, look at baro sensor readings make sure they coincide with your area.

[formulaross]

Also check for vacuum leaks - bad grommets, cracked hoses, hoses to sensors, etc. - Had a '96 Lumina with 'random engine misfire' codes and found 1) a crumbled manifold gromet and 2) a leaking hose going to the MAP sensor. Might also check the high voltage plug wires, rotors, plugs to make there in good shape, not shorted, etc.