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Engine misfire cruising on the highway

Tiny
MICHAELCOX1
  • MEMBER
  • 2000 CHEVROLET SILVERADO
  • 19,300 MILES
Why does my engine misfire when I'm cruising on the highway. This usually occurs when I'm climbing a gradual hill. If I give it gas the vehicle jumps

i have replaced all sensors! Fuel pressure is 50 psi where it is suppose to be lost!
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Friday, October 5th, 2012 AT 12:40 AM

19 Replies

Tiny
SATURNTECH9
  • MECHANIC
  • 30,870 POSTS
Have you looked at the plugs and wires?Is I worse with the ac on?
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Friday, October 5th, 2012 AT 12:51 AM
Tiny
MICHAELCOX1
  • MEMBER
  • 10 POSTS
Hi thank you! I replace the fuel pressure sender, map sensor, all four O2 sensors, fuel pressure reading is 50psi, spark plugs changed 3000 miles ago, I put a computer on it and it said my barometric pressure voltage is 4.25 which I think its suppose to be reading.5 volts. So i'm very lost can you help me? Oh yeah it idles with a little miss and when I first get on the fuel slowly it bucks and chokes misses bad. Then when I kick it down to the next gear it runs fine. But when its in overdrive going up a hill it does the same thing until it kicks into the lower gear. Any help would be appreciated.
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Friday, October 5th, 2012 AT 12:57 AM
Tiny
MICHAELCOX1
  • MEMBER
  • 10 POSTS
Can anyone help please only vehicle I have to get to work and pick up the kids from school
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Friday, October 5th, 2012 AT 1:24 AM
Tiny
SATURNTECH9
  • MECHANIC
  • 30,870 POSTS
When is the baro sensor reading 4.25 volts at idle or with the key on engine off?
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Friday, October 5th, 2012 AT 3:10 AM
Tiny
MICHAELCOX1
  • MEMBER
  • 10 POSTS
At idle or on the throttle
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Friday, October 5th, 2012 AT 11:19 AM
Tiny
SATURNTECH9
  • MECHANIC
  • 30,870 POSTS
Do you have any codes in the computer?
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Friday, October 5th, 2012 AT 1:51 PM
Tiny
MICHAELCOX1
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  • 10 POSTS
No not at all. Im lost.
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Friday, October 5th, 2012 AT 3:51 PM
Tiny
SATURNTECH9
  • MECHANIC
  • 30,870 POSTS
So it never changes from 4.25 volts?
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Friday, October 5th, 2012 AT 4:34 PM
Tiny
MICHAELCOX1
  • MEMBER
  • 10 POSTS
No not at all. So it's at max all the time thinking it needs max fuel.
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Friday, October 5th, 2012 AT 5:21 PM
Tiny
SATURNTECH9
  • MECHANIC
  • 30,870 POSTS
What size engine do you have?
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Friday, October 5th, 2012 AT 5:45 PM
Tiny
MICHAELCOX1
  • MEMBER
  • 10 POSTS
5.3
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Friday, October 5th, 2012 AT 6:19 PM
Tiny
SATURNTECH9
  • MECHANIC
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Here's the crazy part I dont see a baro sensor listed for it.I dont see any trouble codes listed for it ethier.I looked up component locations didnt list on for it. What is the map reading at idle?
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Saturday, October 6th, 2012 AT 1:07 AM
Tiny
MICHAELCOX1
  • MEMBER
  • 10 POSTS
I don't either. Some one said it was run by the map sensor. But I put in a new map. And did not change anything.
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Saturday, October 6th, 2012 AT 1:34 PM
Tiny
SATURNTECH9
  • MECHANIC
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What does the map. Sensor read at idle?
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Saturday, October 6th, 2012 AT 1:53 PM
Tiny
MICHAELCOX1
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I will have to check again lol
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Saturday, October 6th, 2012 AT 1:59 PM
Tiny
SATURNTECH9
  • MECHANIC
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Let me know
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Saturday, October 6th, 2012 AT 2:20 PM
Tiny
MICHAELCOX1
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1.25 v
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Saturday, October 6th, 2012 AT 3:14 PM
Tiny
MICHAELCOX1
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1.25
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Saturday, October 6th, 2012 AT 3:41 PM
Tiny
SATURNTECH9
  • MECHANIC
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Thats about what it should be. How are the spark plug wires?
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Sunday, October 7th, 2012 AT 2:46 AM

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