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FIX IT MAN, Master Technician
Category: GMC
Satisfied Customers: 17406
Experience:  Master Automotive Technician
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I have a 2008 GMC Sierra 2500hd, and I have been having

Customer Question

Hello There! I have a 2008 GMC Sierra 2500hd, and I have been having problems with a random misfire I ran the scanner and all I have is P0300 and I noticed that if I disconnect the Barometer air pressure sensor runs better or smoother but of course gets
me more faulty codes. I have tried change fuel injectors, coils # ***** # ***** because when I have a misfire the computer detects misfire on those cylinders also I have replace the cam sensor ,crack position sensor, wire set, 2 oxygen sensors, and also barometer
pressure sensor. Fuel pressure is 60 psi. and all cylinders are about 195 to 200 psi except for # ***** is 170 to 175 psi, also all injectors are receiving pulse I test them all, also coils have spark so any idea what can be any good help will be appreciated thanks
Submitted: 2 years ago.
Category: GMC
Expert:  FIX IT MAN replied 2 years ago.

Hello, my name is***** for the question. I am assuming this is a 6.0 liter engine? Also, how many miles are on it? Can you actually feel the misfire and if so when does it typically occur?

Customer: replied 2 years ago.
Hello Bobby,
yes you are right is a 6.0 gas motor and the truck has 95,500 miles on it, and when misfire is most when its on idle but also loose power when I push the gas.
Customer: replied 2 years ago.
also with the Barometer pressure sensor plugged the rpms come down to 600 and unplugged goes up to 750 rpms so I have checked most possible air leaks but no luck.
Expert:  FIX IT MAN replied 2 years ago.

Thank you. I have one other question. Does your scan tool read live engine data? If it does can you tell me what the fuel trim readings are when the engine is running?

Customer: replied 2 years ago.
let me hook it up and see but do you need any thing else other than the fuel trim?
Expert:  FIX IT MAN replied 2 years ago.

That is all I need right now. It will give me a good idea of where to start.