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Ask GM Tech (Cam) Your Own Question
GM Tech (Cam)
GM Tech (Cam), Chevy Technician
Category: Chevy
Satisfied Customers: 29534
Experience:  GM Grand Master Technician 2007. 14 years experience.
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Chevrolet Blazer i have been getting a P0171, P0174, and a

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i have been getting a P0171, P0174, and a P0300. i have replaced the maf sensor, checked for vacuum leaks, replaced wires, plugs, rotor, dis. cap, fuel pressure regulator, fuel injectors (whole unit), cat converter, cleaned egr valve, and i am running out of ideas.

Welcome, and thanks for using Just Answer. I am Cam, and I will do my best to assist you. When you are finished please click on accept only if you are satisfied. I don't get paid unless you do.Please do not accept if you cannot leave positive feedback. I don't know if you are a tech or a just working on your own vehicle so we may have to fine tune the answer. I only know as much about your problem as you have told me in your post, so my answers will be based on what you tell me so please add all the details you can. About your vehicle, How about the fuel filter and fuel pump? What is the pressure? 99% of the time those 3 codes are together, it means the fuel filter is plugged or the pump is weak.

60-66 psi is the spec.


Customer: replied 6 years ago.
i have replaced the filter this year, i am working on my own car. i dont have a pressure gadge to test the fuel pressure, i have a code reader machine but i dont think it will tell me the pressure

No, there is not a fuel pressure sensor so you need to get a tool to read the pressure from the port on the rear of the intake fuel lines. I am confident that you will find the pressure is low.


Customer: replied 6 years ago.
i have a ff data

Rpm 2203
cac. load% 22.4
maf 5.93
map 21.9
coolant temp 181
St Ftrm1 0.8
lt ftrm1 13.3
st ftrm2 9.4
lt ftrm2 2.5
mph 26
fuel system 1 closed
fuel system 2 closed

Nope, we need the actual pressure. The fuel trims do indicate the lean condition.


Customer: replied 6 years ago.
the fuel pressure guages i see read only to 15 psi

Wrong type. You need a higher pressure one.


Customer: replied 6 years ago.
pressure reads 50 psi

Is that idling or just with the pump running?


Customer: replied 6 years ago.
with the pump only it was around 53 idling 50

That is too low. Pinch the return line and see if the pressure spikes over 75, if so, then replace the pressure regulator, if not then the pump and filter.


Customer: replied 6 years ago.
is there anyway that a vac. leak could cause low fuel pressure? I just would like to know before i spend another 200 or 300 dollars because i have replaced the filter and regulater.

No, low vacuum should cause higher pressure.


GM Tech (Cam) and other Chevy Specialists are ready to help you
Customer: replied 6 years ago.
i will give it a try, thank you.

No problem.


Customer: replied 6 years ago.
Well, it turned out that my random misfire was caused by the distributor and the other codes was from the vacuum leak