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My van started throwing a 300 multiple misfire code

Tiny
ZACKTHEMACK
  • MEMBER
  • 2004 CHEVROLET VENTURE
  • 150,000 MILES
I changed my spark plugs and wires, Coil, throttle positioning sensor, checked my vacuum lines, my fuel filter was only a month old so I haven't changed it. It idles very roughly and the exhaust is slightly smoky and white. If smooths out a little if I apply the gas but if I am at a light or stop sign I have to throw it in neutral and give it gas or it dies. When it dies it makes a noise like a backfire. Oh and there is a smell of raw gas. Please help. Im getting frustrated.
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Monday, July 2nd, 2012 AT 11:09 PM

8 Replies

Tiny
SATURNTECH9
  • MECHANIC
  • 30,870 POSTS
Have you checked to see if the cat was plugged?
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Monday, July 2nd, 2012 AT 11:14 PM
Tiny
ZACKTHEMACK
  • MEMBER
  • 5 POSTS
I am still seeing a good amount of white smoke out of the tailpipe if it was clogged would it still allow what appears to be a relatively unrestricted discharge? Also I discovered that the rubber hose connected to my pcv valve was pinching closed when the engine was running. I replaced that the with a more rigid one. Dont know how long it was doing that before I discovered that or what effect that it may have had
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Monday, July 2nd, 2012 AT 11:33 PM
Tiny
SATURNTECH9
  • MECHANIC
  • 30,870 POSTS
A pinched colasped pcv hose could cause engine surging while driving. You have white smoke out the tail pipe consantly while it runs?Also you cant always tell by feel etc by how much exhaust is coming out if the exhaust is clogged. You would have to use a back pressure gauge to measure exhaust pressure.
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Monday, July 2nd, 2012 AT 11:39 PM
Tiny
ZACKTHEMACK
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  • 5 POSTS
Yes the smoke is pretty much constant. It will only run for a few minutes then it shutters and dies.
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Monday, July 2nd, 2012 AT 11:49 PM
Tiny
ZACKTHEMACK
  • MEMBER
  • 5 POSTS
Oh and I have to be applying gas to both start it amd keep it running. If I let it idle it dies pretty promptly.
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Monday, July 2nd, 2012 AT 11:50 PM
Tiny
SATURNTECH9
  • MECHANIC
  • 30,870 POSTS
You could have a blown head gasket/cracked head?Have you looked for coolant in spark plug holes?
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Tuesday, July 3rd, 2012 AT 12:24 AM
Tiny
ZACKTHEMACK
  • MEMBER
  • 5 POSTS
That would suck. I changed the spark plugs and didnt notice any coolant. Im at my wits end.
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Tuesday, July 3rd, 2012 AT 12:46 AM
Tiny
SATURNTECH9
  • MECHANIC
  • 30,870 POSTS
That white smoke out the tail pipe scares me go to auto zone and rent a chemical block tester. That will tell you if you have exhaust gases in your coolant.
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Tuesday, July 3rd, 2012 AT 4:26 AM

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