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Ask GM Tech (Cam) Your Own Question
GM Tech (Cam)
GM Tech (Cam), Chevy Technician
Category: Chevy
Satisfied Customers: 29522
Experience:  GM Grand Master Technician 2007. 14 years experience.
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Chevy Suburban: Code p300, Misfiring..vehicles..idles rough

Resolved Question:

Chevy Suburban 2004 5.3 Liter, Code P0300, Misfiring, when idling low the vehicles idles rough. What can this be?
Submitted: 5 years ago.
Category: Chevy
Expert:  GM Tech (Cam) replied 5 years ago.
Hello, I'm Cam. Please include all the details about your issue so I can accurately advise you. I cannot see your vehicle so please be detailed.
What is the 8th digit of your VIN?
Customer: replied 5 years ago.
Z, it is a Chevy Suburban 2004 5.3 Liter, Code was P0300
Expert:  GM Tech (Cam) replied 5 years ago.
YOu need to test the fuel pressure, these are bad for low fuel pressure and causing a misfire. Spec is 48-55 psi and these are common for the pumps failing.
Customer: replied 5 years ago.
We are working on checking out fuel pump...
Expert:  GM Tech (Cam) replied 5 years ago.
Bookmark this page so you can easily navigate back to it, and so you know, you can reply at any time for follow up information regarding this issue, even after you accept my answer and I will reply. Please don't forget to click accept at some time as that is my only means of compensation for assisting you.
Customer: replied 5 years ago.
Fuel Pressure 42 PSI, when vacuum hose is disconnected from fuel pressure regulator it goes to 52 PSI...
Expert:  GM Tech (Cam) replied 5 years ago.
What is it with only the pump runing and does it hold when you turnit off?
Customer: replied 5 years ago.
42 PSI while running pump only
Expert:  GM Tech (Cam) replied 5 years ago.
Too low, you need a new pump.
Customer: replied 5 years ago.
The fuel pump has already been replaced that was the original repair & it came back misfiring....
Expert:  GM Tech (Cam) replied 5 years ago.
Ok then the fuel pressure regulator is dropping the pressure.
Customer: replied 5 years ago.

But the Fuel Presssure Regulator is not leaking...& the car starts right away with no problems..

Expert:  GM Tech (Cam) replied 5 years ago.
OK, but if the regulator is allow the pressure to cut out at 42 with the engine off, then it is too low and opening too early. It need not be leaking to be faulty.
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