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1998 Chevy Blazer Code P0108

Tiny
JAMESJAM
  • MEMBER
  • 1998 CHEVROLET BLAZER
Engine Mechanical problem
1998 Chevy Blazer 6 cyl Four Wheel Drive Automatic

Help, I have a code P0108. We tested the Map sensor and found it was bad. We replaced it and still get the code. I have check all the wires and found nothing wrong. I dont know where to go from here? There are no other codes. The blazer will start and run good when cold. Thats about 300 yards. Then starts missing very bad untill it stalls. The cat conv has been removed and fule pressure is good. The fuel filter has been replaced. Help.
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Thursday, August 14th, 2008 AT 8:39 PM

15 Replies

Tiny
MASTERTECHTIM
  • MECHANIC
  • 4,749 POSTS
On the fuel tank there is a sensor that looks exactly like a map sensor. Its a fuel tank pressure sensor. Unplug it and see if it runs good. I have seen these short out and bring down the 5v reference on the map sensor causing it to die. Let me know
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Thursday, August 14th, 2008 AT 8:47 PM
Tiny
JAMESJAM
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  • 10 POSTS
Will I haft to drop the tank?
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Thursday, August 14th, 2008 AT 9:03 PM
Tiny
JAMESJAM
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  • 10 POSTS
Ok I know I haft to drop the tank but is there a easier way?
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Thursday, August 14th, 2008 AT 9:17 PM
Tiny
MASTERTECHTIM
  • MECHANIC
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Ou dont have to drop the tank, you should be able to reach up and unplug it
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Friday, August 15th, 2008 AT 6:04 AM
Tiny
JAMESJAM
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  • 10 POSTS
I found the sensor and unplug it It still runs rough.
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Friday, August 15th, 2008 AT 3:24 PM
Tiny
MASTERTECHTIM
  • MECHANIC
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Have you checked cap and rotor? Coolant temp sensor? If wiring to sensor and the sensor are good then check the egr valve for a piece of carbon bouncing around in it. Also lightly pull on wires to map sensor to make sure the wire is not broken inside the insulation.
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Friday, August 15th, 2008 AT 3:39 PM
Tiny
JAMESJAM
  • MEMBER
  • 10 POSTS
The cap and rotorare new. The erg valve was pulled and clean and all the wires seem ok, I havent gone thru the check on the temp sensor, but I did unplug it and it didnt make any differance. I am at a total loss. Do you think I should perform the test on the temp sensor, even if it didnt make any differance?
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Friday, August 15th, 2008 AT 5:17 PM
Tiny
MASTERTECHTIM
  • MECHANIC
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I would recheck test on map sensor and make sure all the voltages are correct. You either have a loss of engine vacuum at the map port, wiring from pcm to map or bad pcm I would suspect. Its hard to give a real accurate diagnosis without driving vehicle but the 108 we need to get to the bottom of. Do you have access to a scan tool to actually watch map voltage to see if it is working at all? Thats what I would do next.
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Friday, August 15th, 2008 AT 8:07 PM
Tiny
JAMESJAM
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  • 10 POSTS
Ok, after working on the wireing and going back over the everthing else, I dont have a engine code any more. I have run and run it no code. However, when it gets warm it still cuts out. I cant rev the motor. I did drive it and it went much further. I am pulling a spark plug to see the condition. Do you have any Ideas now?
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Sunday, August 17th, 2008 AT 10:16 AM
Tiny
JAMESJAM
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  • 10 POSTS
Plugs look good
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Sunday, August 17th, 2008 AT 10:26 AM
Tiny
JAMESJAM
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  • 10 POSTS
We have discovered that the coil voltage is 8 volts, I think its should be 12 volts what should I do?
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Sunday, August 17th, 2008 AT 12:00 PM
Tiny
MASTERTECHTIM
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Now we are onto something. You need 12 volts atleast. Run a jumper wire from the battery and see if it runs. Then we can chase that circuit
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Sunday, August 17th, 2008 AT 6:42 PM
Tiny
JAMESJAM
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  • 10 POSTS
Theres is two wires on the coil, The red or pink wire is pos. And the white is the neg. I hook them up to the battery and a large spark. Just like it was a direct short. Is this ok?
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Sunday, August 17th, 2008 AT 7:33 PM
Tiny
JAMESJAM
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Ok I got brave and put the wires on and for some reason it wouldnt start. I dont know why?
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Sunday, August 17th, 2008 AT 7:46 PM
Tiny
MASTERTECHTIM
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The pink wire is the battery feed wire. With key on does this wire have 12 volts? With the connector unplugged?
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Tuesday, August 19th, 2008 AT 6:23 AM

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