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Miss fire when climing hill

11-18-2010, 06:23 PM
I have a 2002 4.3l 4 dr S-10 with automatic trans.
Every time i go up a steep hill my service engine light flashes, according to the manual that means there is a miss fire.
It only happends when going up a hill for a while then stops and comes back on again.
What would make this happen does anyone have any idea..
I have replaced plugs, wires also put new fuel pump, and filter..
any suggestions would be helpfull.

11-18-2010, 09:45 PM
Does the tranny have overdrive? If you downshift, does the problem go away? Any applicable trouble codes?

11-19-2010, 06:00 PM
yes the tranny does have over drive, even when it is taken out of od it still does it.
it comes up PO300 cylinder misfire comes off when i stop but as soon as i start up the hill again it comes back on

11-19-2010, 09:20 PM
P0300 DTC along with a flashing SES light is almost always caused by secondary ignition failures: Spark plugs, spark plug wires, distributor cap and rotor, ignition coil. Always use AC Delco plugs, cap and rotor in the 4.3L, they are very fussy. Put a dab of silicone dielectric grease on each terminal, inside and out, of the distributor cap. Post your results.

11-20-2010, 02:27 PM
could be the knock sensor

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