1987 Chevy Celebrity Hesitation /Hard starting

1987 CHEVROLET CELEBRITY
110,000 MILES • 6 CYL • FWD • AUTOMATIC
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BHAZELETT
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It started running really rough like it had water in the fuel. We ran "HEET" through for one tank of gas, it ran a little better, but deffinitely not right. Since then the shop has installed an ECM, Plugs, Wires, Map sensor, Injectors. It runs better, but now it's hard starting cold and has a hesitation when accelerating warm or cold, but the rough running is gone. It has 40#'s fuel pressure. A sampling of the fuel looks clear. We've run 3 tanks of fuel through it with this problem. Any ideas would be helpful.

Thanks
Oct 18, 2009 at 12:53 AM
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RASMATAZ
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Possible Causes of Engine 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
Oct 18, 2009 at 1:06 AM