1993 Chevy Suburban hesitation when accelerating

1993 CHEVROLET SUBURBAN
138,000 MILES • V8 • 4WD • AUTOMATIC
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1MADDOG
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350 cc (5.7 ltr) engine. The suburban has a hesitation - mostly when accelerating after a stop. It doesn’t hesitate if I push the gas hard, but does when I try to start slowly. I’ve also noticed that it will sometime do it on the highway while using cruise control, but usually when the cruise kicks out as it reaches the set speed. It doesn't happen when the cruise kicks back in to maintain speed.

I changed the plugs thinking it might be skipping a little. They needed to be changed, but they weren’t terrible. No oil residue or built up carbon, so I assume there is no valve leaks or compression problems. Gas filter in fairly new and it's not acting as if the fuel pump is going bad.

One other thing I've noticed, when idling, the tachometer use to sit around 750-850 and now seems to rev back and forth between that and about 300 or 400 every second or two.

Ideas?

thanks
Jul 28, 2009 at 10:58 AM
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RASMATAZ
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Hesitating or stumbling

Dirty fuel injectors (cleaning the injectors often fixes this).
Bad MAP (manifold absolute pressure) sensor
Bad TPS (throttle position) sensor
Bad or dirty MAF (mass airflow) sensor
Low fuel pressure (leaky fuel pressure regulator or weak fuel pump)
Vacuum leaks (intake manifold, vacuum hoses, throttle body, EGR valve)
Bad gasoline (fuel contaminated with water or too much alcohol)

Sometimes, what feels like a hesitation is actually ignition misfire rather than lean misfire. The causes of ignition misfire may include:

Dirty or worn spark plugs
Bad plug wires
Weak ignition coil
Wet plug wires
Jul 28, 2009 at 1:20 PM
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1MADDOG
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Thanks, I will give those things a look over.
Aug 3, 2009 at 5:14 AM
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