97 GMC Suburban bad hesitation when cold.

[dougd5652]

I have a 97 k1500 Suburban 4X4 with a 5.7 with 255K. The truck started missing/hesitating during initial acceleration only when cold about 6 months ago. When it is failing I can hear/feel the miss with truck in park and giving gas. I have recently done the following to try and fix. ACDelco plugs/wires/cap/rotor/coil. A new fuel pump was install 1.5 years ago. Not sure of brand. New Fram fuel filter. Unrelated I also installed a rebuilt tranny. I have checked the distributer for play. It seems fine. Really feels more like a fuel issue. Any help would be greatly appreciated. Thanks Doug

Been 4 days...thanks for all of help...

[CalifOkie]

An engine running rough when it is cold and then smoothing out as it warms up is usually a sign that the ECT (Engine Coolant Temperature sensor for the computer) is faulty. The only way of verifying this is to use a scanner on it before the engine has been started first thing in the morning. Turn the key on without starting engine and scan engine data. Look for the ECT temperature and the IAT (Intake Air Temperature Sensor) Temperature. They should be within a few degrees of each other. If they are not replace the ECT which should be located on or near the thermostat housing. Be sure you replace the ECT for the computer and not the one for the guage (some have two). Your parts man can give you the correct one you need then you can find out which one you are replacing because the plug configurations are different on the two different sensors.