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engine runs rough w/random misfire.4.3vortec
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Brian Stults
New User
Sep 14, 2011, 3:27 PM
Post #1 of 4
(5109 views)
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engine runs rough w/random misfire.4.3vortec
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i have a 2000 astro w/4.3liter vortec v-6. my van was running great driving down the road one day and then just died. i coasted into a residential neighborhood and stopped near a mechanics house. he walked over and we worked on the van and he took the coil from a camaro in his driveway and put it on my van and it started right up. ran great for another 3 months then suddenly died again one day except this time it started again. i drove home and the next day (weather had changed from nice warm day to cold and rainy overnight) when i started it there was a loud noise (kind of like if you leave the parking brake on and start driving) when i put it in reverse and the motor was running very rough. the noise stopped soon after i started driving but hasn't stopped missing. i have changed plugs, wires, distributor cap, ignition coil, and rotor, and it still misses terribly throughout driving. i took the timing chain cover off to see if it had jumped time but the chain looks fine and i'm not sure it would be possible for it to jump time on this van. put new timing chain cover on and am wondering if i should replace the ignition control module? and what about the crankshaft positioning sensor?
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Hammer Time
Ultimate Carjunky
/ Moderator
Sep 14, 2011, 3:44 PM
Post #2 of 4
(5099 views)
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Re: engine runs rough w/random misfire.4.3vortec
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All "crank, no start" conditions are approached in the same way. Every engine requires certain functions to be able to run. Some of these functions rely on specific components to work and some components are part of more than one function so it is important to see the whole picture to be able to conclude anything about what may have failed. Also, these functions can ONLY be tested during the failure. Any other time and they will simply test good because the problem isn't present at the moment.
If you approach this in any other way, you are merely guessing and that only serves to replace unnecessary parts and wastes money.
Every engine requires spark, fuel and compression to run. That's what we have to look for.
These are the basics that need to be tested and will give us the info required to isolate a cause.
1) Test for spark at the plug end of the wire using a spark tester. If none found, check for power supply on the + terminal of the coil with the key on.
2) Test for injector pulse using a small bulb called a noid light. If none found, check for power supply at one side of the injector with the key on.
3) Use a fuel pressure gauge to test for correct fuel pressure, also noticing if the pressure holds when key is shut off.
4) If all of these things check good, then you would need to do a complete compression test.
Once you have determined which of these functions has dropped out,
you will know which system is having the problem.
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We offer help in answering questions, clarifying things or giving advice but we are not a substitute for an on-site inspection by a professional.
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Brian Stults
New User
Sep 14, 2011, 4:01 PM
Post #3 of 4
(5081 views)
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Re: engine runs rough w/random misfire.4.3vortec
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okay i will need more tools to do all of that but maybe this would be useful info. i had the van running one day and pulled the spark plug wires from the left side of the dist. cap i believe 1,3,and5 cylinders and the van continued to run the same
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Hammer Time
Ultimate Carjunky
/ Moderator
Sep 14, 2011, 4:09 PM
Post #4 of 4
(5078 views)
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Re: engine runs rough w/random misfire.4.3vortec
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You may have a leaking fuel pressure regulator but that will require some testing to find out.
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We offer help in answering questions, clarifying things or giving advice but we are not a substitute for an on-site inspection by a professional.
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