I have a 92 chevy truck 4.3 liter. The truck starts fine and idles good. While accelerating the truck will hesitate or stutter. It doesn't do it all the time, but quite often. I put new plugs and wires, cap and rotor,pcv valve, and fuel filter. Didn't help. Any suggestions.
Look at the ignition coil closely for ''gray'' marks around the coil which are signs of arcing. Went crazy with my 89 Blazer with the erratic under load misfire until I finally saw it arcing with the hood up one night by chance. It only did it few times idling. PS stay away from cheapo Auto Zone coils, they start doing the same after a few weeks. I put a NAPA coil in for good...
Agreeing with 'R-man', you can watch under the hood at night while someone holds his foot on the accel. while CAREFULLY HOLDING the brakes--this load should make it arc where/if electrically defective. s
check throttle position sensor with a voltmeter on the "signal" or "data" wire. since the other two wires are +5v and ground respectively, it's pretty easy to figure out which one of the 3 is the signal wire. turn key on, but don't start vehicle, & measure voltage on the data wire. while watching meter, slowly rotate the throttle from closed to open. voltage should change slowly & steadily. if at any point while rotating it spikes or otherwise fluctuates, then just as quickly returns to smooth operation, or you get no voltage change at all, the TPS is bad. takes 5 minutes to test, & about 2 to replace if it's bad. TPS's wear out more rapidly than most people realize - all they are is a potentiometer.... like the old volume knobs on a stereo. they have brushes inside that slide across a graphite back, & will wear out & cause intermittent readings - making the ecm think the pedal is somewhere other than where it actually is, causing all kinds of problems. on cars without a throttle position sensor, you would be checking the mass airflow sensor, since it has a mechanism that is nearly identical to track movement, and will cause all the same problems.
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