Join Date: Mar 2002
Location: Austin, TX, USA
Look for vacuum leaks. Are the sealing tips or o-rings properly installed on the fuel injectors? Try waving propane from a torch around (unlit) gasket areas and the fuel injectors - see if RPMs change. Some folks use WD-40. A vacuum leak is a high probability.
Put an ohm meter accross the terminals of your throttle position sensor and see if the resistance changes smoothly as you slowly open the throttle by hand.
Check your fuel pressure again, but this time pull a vacuum on the fuel pressure regulator (near the end of the fuel log) and see how pressure changes with vacuum. It should decrease with vacuum and supply adequate pressure with zero vacuum.
Is idle speed OK? Does it idle fast when cold started but idle down on it's own after a couple minutes (depending on the temperature)? If not, the the idle air control motor may be sticky, but that shouldn't affect hesitation.
Consult a service manual for how to check the manifold absolute pressure sensor (MAP). The procedure probably consists of back-probing the connector and measuring DC voltage accross two of the pins looking for a specific voltage change. If you have a mass air flow sensor (MAF), check the procedure on checking it, which should be similar to the MAP procedure.
Does the check engine light come on for a few seconds prior to cranking the motor over? It should as a lamp-test. If not, then you may really have a code, but can't see the light flash.