2001 gmc sierra stepside pops

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  #1  
Old 06-13-04, 08:51 AM
jeff moralez
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2001 gmc sierra stepside pops

through the carborator and wont start. The other day my daughter said that her truck was dieseling and studdering as she puts it. Then she goes to Office depot and noticed after she turned it off, spitting and sputtering briefely.When she came out it would not start .I checked and get spark to all cyls and the fuel rail has gas spewing out of the shrader valve when depressed and key is on.There was a big o tire shop that had a diagnostic tool when hooked up it displayed bad o2 sensor and throttle posistion sensor(old codes I imagine because my daughter does no maintenance). .I didnt think this would keep it from starting but bought a throttle sensor and before installing I compared the new readings to the old one and they were Identical so its a good sensor.If you turn it over it spits and backfires through the carb like it is out of time. It also seems to hit once or twice like it wants to start then it acts like it is out of time and then abrubtly hits against ityself and the engine stops turning over momentarily then it will turn over some more spitting and back firing through the carb but wont start.I understand that there is also a crank sensor and cam sensor ,could one of these be causing the trouble? I have also taken the distributor cap and rotor out and inspected . the module is out also for bench testing however the local auto parts cant check this particular module so maybe Ill buy one and try that. Could I have a bad computor sending the wrong firing order?This is a 4.3 v-6 with 38k miles. Thanks to all that can lend a clue.
Jeff
 
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  #2  
Old 06-13-04, 11:30 AM
billys68ss's Avatar
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First of all you dont have a carburetor.... You have a throttle body.... totally different animals.
Second.... if it is backfiring then you have a timing issue, or internal failure.
Since you said that it had some diagnostic trouble codes why not post them here before you throw any more parts at it and let us see if we can help you out. Just because your daughter doesnt do maintenance doesnt mean the codes are "old" They are there because something is amiss.
With 38k miles, do you have any warranty left? Not sure about GM's warranty.
Hope this is helpful to ya,
Billy
 
  #3  
Old 06-13-04, 02:02 PM
jeff moralez
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The trouble codes were throttle sensor and o2 sensor. No waranty. No misfire codes. Ill check back later .Thank you.
jeff
 
  #4  
Old 06-15-04, 02:01 PM
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Check the fuel pressure with a guage,pushing on the valve to check for fuel is not a valid test.You should have 60-66 psi with the key turned on,cycle the key several times waiting 10 seconds between on and off.If you can't get 60 psi it won't start.At that point remove the air intake hose and spray carb cleaner in the intake.It it fires and then dies I would bet on a fuel pump.I would check the fuel filter first however.
 
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