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Code P0300 after replacing thermostat

Tiny
JAYB1214
  • MEMBER
  • 1996 CHEVROLET S-10
  • 6 CYL
  • AUTOMATIC
  • 192,000 MILES
I changed the thermostat on my truck. When I started it up I got a p0300 code. Could I have knocked something loose anywhere?
Saturday, April 9th, 2011 AT 11:55 AM

11 Replies

Tiny
JDL
  • MECHANIC
  • 16,098 POSTS
That is a random misfire, you might have got something wet. Are there any driveability issues? Why were you checking codes, any particular reason?
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Saturday, October 3rd, 2020 AT 11:43 AM
Tiny
JAYB1214
  • MEMBER
  • 7 POSTS
It will barely go down the street. I did not check the code until the engine light came on.
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Saturday, October 3rd, 2020 AT 11:43 AM
Tiny
JDL
  • MECHANIC
  • 16,098 POSTS
Did you have the light before you worked on it? How long since a tuneup? Use a gauge and check fuel pressure. Plugs--plug wires, distributor cap and rotor all okay?
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Saturday, October 3rd, 2020 AT 11:43 AM
Tiny
JAYB1214
  • MEMBER
  • 7 POSTS
I changed the plugs and wires and it ran okay for about a day then back to the same thing.
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Saturday, October 3rd, 2020 AT 11:43 AM
Tiny
JDL
  • MECHANIC
  • 16,098 POSTS
How about the fuel pressure? Some of the national brand autostores used to loan out a fuel pressure gage. Do you have the spider fuel system on this? They are noted for problems.
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Saturday, October 3rd, 2020 AT 11:43 AM
Tiny
JAYB1214
  • MEMBER
  • 7 POSTS
I am not really sure. Is there a way to tell?
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Saturday, October 3rd, 2020 AT 11:43 AM
Tiny
JDL
  • MECHANIC
  • 16,098 POSTS
The Napa parts book shows you have the spider fuel system.
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Saturday, October 3rd, 2020 AT 11:43 AM
Tiny
JAYB1214
  • MEMBER
  • 7 POSTS
Okay, I will not be able to do anything until Monday. Thanks for your time.
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Saturday, October 3rd, 2020 AT 11:43 AM
Tiny
JDL
  • MECHANIC
  • 16,098 POSTS
No problem, have a good evening.
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Saturday, October 3rd, 2020 AT 11:43 AM
Tiny
GLYN ROB
  • MEMBER
  • 2 POSTS
I am having the p0300 code too. Engine starts and runs great. 2003 s10 4.3 I have changed about every part except the ICM and spider injector. Soon as I get a fuel pressure tester I will check that. On my obd2 reader it shows ignition advance at 17 degrees idle and 45 degrees driving.
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Saturday, October 3rd, 2020 AT 11:43 AM
Tiny
KEN L
  • MASTER CERTIFIED MECHANIC
  • 47,643 POSTS
I have seen the spider injector, weak fuel pump and the MAF sensor cause this code. Do not worry about the timing that sounds normal. Here is how you can check the fuel pump:

https://www.2carpros.com/articles/how-to-check-fuel-system-pressure-and-regulator

(55-62 psi)

Please run down this guide and report back.

Cheers, Ken
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Saturday, October 3rd, 2020 AT 11:43 AM

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