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Old 10-19-2016, 12:12 AM   #1
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Default Need help po300 code

Changed plugs and wires,tested coils and fuel pressure, cleaned maf sensor and fuel injectors
What else can I do truck still has no power and runs very rough. I also changed the 02 sensors in front of the cat
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Old 10-19-2016, 01:46 PM   #2
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Check exhaust back pressure?

Any codes set?
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Old 10-19-2016, 01:52 PM   #3
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Quote:
Originally Posted by mamerson2003 View Post
Changed plugs and wires,tested coils and fuel pressure, cleaned maf sensor and fuel injectors
What else can I do truck still has no power and runs very rough. I also changed the 02 sensors in front of the cat
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Check exhaust back pressure?

Any codes set?
Only codes I get are po300 and po332 for the knock sensor. Is it possible that the cats are causing my problem
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Old 10-19-2016, 05:30 PM   #4
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I've seen a completely clogged cat cause low performance/sluggish, but never cause it to run rough.

How'* your coolant level?
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Old 10-29-2016, 03:53 PM   #5
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I've seen a completely clogged cat cause low performance/sluggish, but never cause it to run rough.

How'* your coolant level?
Coolant Level........good call, Mike. I've seen misfire symptoms occur with low coolant quite often.

One other thing to check is the dash temperature guage. If the coolant level is appropriate, but the dash guage indicates a "cold" temperature, the problem could be a bad coolant temperature sensor. With no coolant temp input, the ECM "thinks" the engine is running at -40 degrees causing random misfires to occur.

Had this prob on a TrailBlazer a while back when I replaced the head gasket.......forgot to reattach the temp sensor and didn't figure it out for a day. Reconnected the temp sensor and the misfires went away immediately.
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