Expert: Robert Summers - 10/26/2007

Question
HESITATION WHEN WARMED UP STUTTERING WHEN COLD STARTS RUNS LIKE NEW. I HAVE REPLACED: DIST, COIL, WIRES,TPS, MASS AIR, TEMP INTAKE SENSOR,I HAVE 110K ON SUBURBAN THE FUNNY PART IS RUNS FINE WHEN I FIRST START HITS ON ALL 8 SMOOTH I LIKE IT..THEN AS IT WARMS OR I RESTART AND DRIVE I FEEL THIS ANNOYING HESITATION... STUMBLE, IF I HOLD THE THROTTLE AT 1500 STARTING OUT IT JUST ROUGH IF I DEPRESS THE THROTTLE IT RUNS BETTR BUT HAS THE SLUG FEEL UNLIKE WHEN I FIRST START. I HAVE TRIED THE ABOVE..COULD IT BE EGR? O2?PCV? WHAT WOULD YOU RECCOMEND. FUEL INJECTED THROTLE BODY 7.4
THANKS
JIMMY

Answer
Hi James. two things to check... timing chain. once warm pull dist cap and turn crank by hand and see how far you can turn before dist rotor starts to move, should move almost right away. too much slak in chain would cause it to wander out of time. also try once warmed up fuel pressure and see if it drops off from when engine cold. pressure should be the same hot or cold.   Hope this helps