Any suggestions? My 96 Winstar has an intermittent miss only on cylinder 3. The mis will occure anywhere from 1 or 2 times a minute to nothing for 10 - 15 minutes. Misfire occures when cold (in open loop) and when the engine is at operating temp. Zero evidence of coolant into this cylinder. MIL on. My scanner gives P0303 Misfire #3. Vacume guage is steady at 21 inches hg, except for a down flick of less than 1 inch on a misfire. With the vacume guage attached, gooseing the engine up to around 2500RPM showed a quick drop to zero, a recovery to about 26 in hg and settle back to 21 in hg.
Swapped plug wires 2 /3 and 4/5. Swapped spark plugs 2/3 and 4/6, then replaced the year old Bosch w/ a set of Autolite Platinum's.
Checked the coil pack. Resistance was out of spec. Replaced it. No change. The new coil pack was with-in specs listed in the Haynes manual.
EGR ports are clean! I cleaned them last year when I replaced the intake manifold gaskets. (had a AF leek into the #1 intake valve). I checked them again to verify they were all clear.
Disconnected the EGR to see if a possible block in the passage. No difference.
Swapped fuel injectors #3 with #2. problem stays with #3. Checked the wiring to #3 injector. near 0 resistance and no deflections when I wiggle the connections, including the plug that passes from the main harness to the Intake wiring harness.
Compression test was somewhat high on all cyllinders. Minimum is 101 psi. All 6 tested between 200 and 215 on 4 cranks.
None of the changes listed above altered the misfire.
Except for the PCM, I don't know of anything that would affect just 1 cylinder.
I would expect a sticking valve to show a much larger down flick on the vacume gauge.
Swapped plug wires 2 /3 and 4/5. Swapped spark plugs 2/3 and 4/6, then replaced the year old Bosch w/ a set of Autolite Platinum's.
Checked the coil pack. Resistance was out of spec. Replaced it. No change. The new coil pack was with-in specs listed in the Haynes manual.
EGR ports are clean! I cleaned them last year when I replaced the intake manifold gaskets. (had a AF leek into the #1 intake valve). I checked them again to verify they were all clear.
Disconnected the EGR to see if a possible block in the passage. No difference.
Swapped fuel injectors #3 with #2. problem stays with #3. Checked the wiring to #3 injector. near 0 resistance and no deflections when I wiggle the connections, including the plug that passes from the main harness to the Intake wiring harness.
Compression test was somewhat high on all cyllinders. Minimum is 101 psi. All 6 tested between 200 and 215 on 4 cranks.
None of the changes listed above altered the misfire.
Except for the PCM, I don't know of anything that would affect just 1 cylinder.
I would expect a sticking valve to show a much larger down flick on the vacume gauge.
