Mechanics

MY VAN STARTED THROWING A 300 MULTIPLE MISFIRE CODE

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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Zackthemack
July 2, 2012.



Have you checked to see if the cat was plugged?

Saturntech9
Jul 2, 2012.
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

Tiny
Zackthemack
Jul 2, 2012.
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.

Saturntech9
Jul 2, 2012.
Yes the smoke is pretty much constant. It will only run for a few minutes then it shutters and dies.

Tiny
Zackthemack
Jul 2, 2012.
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.

Tiny
Zackthemack
Jul 2, 2012.
You could have a blown head gasket/cracked head?Have you looked for coolant in spark plug holes?

Saturntech9
Jul 3, 2012.
That would suck. I changed the spark plugs and didnt notice any coolant. Im at my wits end.

Tiny
Zackthemack
Jul 3, 2012.
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.

Saturntech9
Jul 3, 2012.