By stutter you presumably mean it misfires? Most hesitations and misfires by far are caused by an ignition problem - low output from coils, worn spark plugs and suchlike though bad injectors or low fuel pressure can play a part.
Every diagnostic process should begin with a thorough visual underbonnet inspection and a code read.
CHECK THE IDLE SPEED SENSOR, UNPLUG IT AND SEE IF THE VEHICLE REVS UP A BIT. IF IT DOES, THEN REPLACE IT. ALSO CHECK THE FUEL PUMP RELAY IN THE FUSEBOX. HOPE THIS HELPS. .LET ME KNOW. GOOD LUCK
SOURCE: my son's gmc 4.3l hesitates upon acceleration. I
do you have any check engine lights on? If you do, that is the first thing I would have checked. It does sound like plugged EGR, vacuum leak, or bad TPS
SOURCE: 1989 GMC 2500 5.7L - engine surges and stalls at idle. Loses power at cruising speed.
Wow you have replaced a lot of stuff. Lets go back to the Fuel pump. When you replaced it did you replace the hose between the pump and the sending unit. These are common for splitting. Have you hooked up a fuel pressure gauge to check what pressure you have? It should be real close to 13 psi and should raise to at least 18 or 19 when you pinch off the return line.
SOURCE: 1999 Grand Am 3.4litre idle problems. Starts rough
it sounds like you have a injector leaking down into one of your cylinders so it is flooding out a cylinder thus runs rough and long cranks.
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Turned out to be a bad egr vac. Selinoid, and clogged egr valve...so far so good.
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