1996 Chevy Astro 4.3 L V-6 with 72,000 miles

Tiny
2HOWARDS
  • MEMBER
  • 1996 CHEVROLET TRUCK
In the morning I have an intermittent hesitation. This is more pronounced if I pull a trailer. 2 times the check engine light has come on and my wife has driven it straight to a parts store and the scanner reports a P0300 and only a P0300. Upon restart the light is out and it is random as to when it will happen again (2 times in 8 months). 15 minutes of driving will clear this condition up unless you are at highway speed pulling a trailer then a slight miss or surge can be felt (no dash lights come on). I do have some factory manuals (bought used) and have worked on cars in the past. Here is what I have checked. Fuel filter within the last 10,000 miles. A fuel sample was taken and it is clear. Fuel pressure during the event (remains steady between 45 and 60 lbs depending on load). Pulled the plugs and when I did the wires broke so new wires, cap, rotor and plugs. (AC plugs, NAPA wires cap and rotor).
Switching unit (GM part). Knock sensor does produce voltage as per the factory test. I did not check the crank signal however the car is running so I figured that it would more e severe concerns if that was a problem. Checked coil using resistance test and it passes. Fluid levels are ok and not overdue for service. Spraying water on the engine does not create the problem.
Is it possible to disconnect the lock up T/C to see if this is the problem? Condition is not limited to 1st gear. This will happen in any gear until it’s warmed up then the problem disappears. To aggravate the problem I pull my trailer. I did pay the local dealer to look at it but after 2 hours Diagnostic time they said to bring it back when it is more consistent.
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Monday, January 22nd, 2007 AT 11:01 PM

3 Replies

Tiny
CARUNDELL
  • MEMBER
Hey 2,
A p0300 (random misfire) can be a toughy to diagnosis. Let me do some research and will get back to ya with some other things to test!

Chris
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Tuesday, January 23rd, 2007 AT 4:46 AM
Tiny
ASTRO
  • MEMBER
You say this problem starts out when engine is cold, then after warm-up it's fine. This leads me to believe the vent holes in the distributor housing are clogged.
I have a 2000 and ran into same. GM put out a service note about this problem. If your van's distributor-housing has screens in these vent holes, remove the screens. If you don't have screens, like mine, I simply ran a drill bit through the holes to clear out the little plastic pieces that are "stair-stepped" in there. Condensation forms in the distributor cap at night, and it's still there in the morning, if it can't breathe, it can't dry out. Hope this helps!
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Monday, March 19th, 2007 AT 6:16 PM
Tiny
TUSCANO1
  • MEMBER
I have the same problem with my Blazer, it is a small valve in the transmission, I forget what it is called, but my brother-in-law is a tranny specialist for GM, and he told me it was an easy job to do and inexpensive, he's fixing mine next week.
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Friday, September 7th, 2007 AT 4:52 PM

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