Was running fine and until i pulled up to a stop light and notice it shaking alittle funny when i was sitting and sounding rough. now it backfires constantly but still will eventually get up to speed. it is now throwing codes 143 144 146 and 300. i just replaced the final original 02 sensor so it may not be throwing all those codes still. haven't had time to put the scanner back on yet. also its a 4.3 automatic. checked spark plugs all seemed well just one was alittle moist.
SOURCE: 02 GMC Sierra 4.3 V6 P1345
Well that sounds like a tough one , But here is a site worth checking out . Several mechanics use this it to help out people like your self that are frustrated and are getting P #$%$# off ! Good luck
http://www.obd-codes.com/forums/search.php?search_id=active_topics
SOURCE: 2005 Jimmy 4X4, 4.3L, P300 multiple misfire. Have
Try some injector cleaner in the fuel--there might be some water in the fuel also. Check the air cleaner.
SOURCE: 95 GMC Sierra 4x4 350 5.7 rough idle problem
It sounds like a MAP sensor going bad. MAP is short for manifold absolute pressure sensor, it senses the manifold pressure and applies the right amount of gas with the right amount of ignition timing so the car runs and performs well if this does not work properly. It throws off the whole loop cycle for the computer, which in turn makes it run badly and get poor fuel economy. It can causes the engine to have a lack of power, combined with a loss of fuel economy. Poor take offs and sometimes an occasional stalling may occur if the MAP sensor is faulty and sending the wrong signals to the ECM.
Hope this helps and thank you for using Fixya.
Here is a link that my help you in the future.
http://www.troublecodes.net/GM/
SOURCE: Had the spark plugs and
If your Safari did not expecience these systoms prior to you changing the plugs and ignition wires, then you may have crossed two or more of these wires when they were repalced.
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