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I have a 2000 chevy 2500 hd 6.0, throwing a p0300 random…

Customer Question
I have a 2000...

I have a 2000 chevy 2500 hd 6.0, throwing a p0300 random misfire when you are crusing along the check eng line flashes away, i put a fuel pressure gauge on it, and at idle its 54/58 needle jumping away, when i raise the rpm to 2000 the pressure goes from 50/56 needle jumping away the entire time have replaced fuel pressure regulator and vac line to it

Mechanic's Assistant: How many miles are on the vehicle? And when was the last time it was serviced?

109k

Mechanic's Assistant: What is the model of your '00 Chevy?

2500 hd

Mechanic's Assistant: Are you fixing your 2500 yourself? What have you tried so far?

Replaced fuel pressure regulator and vac line tune up

Mechanic's Assistant: Anything else you want the mechanic to know before I connect you?

I have a 2000 chevy 2500 hd 6.0, throwing a p0300 random misfire when you are crusing along the check eng line flashes away, i put a fuel pressure gauge on it, and at idle its 54/58 needle jumping away, when i raise the rpm to 2000 the pressure goes from 50/56 needle jumping away the entire time have replaced fuel pressure regulator and vac line to it

Submitted: 7 months ago.Category: Chevy
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Answered in 8 minutes by:
12/1/2017
Chevy Mechanic: Chris (aka-Moose), Technician replied 7 months ago
Chris (aka-Moose)
Chris (aka-Moose), Technician
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When you did these pressure readings was it misfire at that time?

Can you do these pressure readings while driving and tell me the pressure then as well as the terrain, speed, and rpm?

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Customer reply replied 7 months ago
pressure readings were taken in the garage idling, cant take them driving.the check engine light only comes on when truck is off idle, and averaging 2000-2700 rpm, when the check engine light comes on when you are driving if you hammer down wot, the light shuts off immediately, other wise it will flash away, so in the garage pressure gauge hooked up the pressure needle is alway bouncing was told it's supposed to be steady? if i unplug the vac line off the fuel pressure regulator pressure jumps to around 63 psi and high idle to the problem rage of 200/2800 the light dont come on, but if i leave the pressure regulator vac line on it does
Chevy Mechanic: Chris (aka-Moose), Technician replied 7 months ago

Does your fuel gauge have a hose where as you can run it out the back of the hood and zip tie the gauge to the wiper arm so you can view it while driving. I would hate to go this route that pressure is to blame for sure to find out we are barking up the wrong tree. Yes, it should be steady but is it too fluctuating during the misfire. That is what we need to know.

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Chevy Mechanic: Chris (aka-Moose), Technician replied 7 months ago

Thanks for checking that. Since the specs are 5562 and you are dropping below those specs with a new regulator, this should indicate the pump is not strong enough any longer and most likely the cause of the misfire.

Now that I have posted a partial or complete answer, you will see you can rate me. The deposit you have already paid is not transferred to me until you rate me. I would like to receive nothing less than 5-star excellent ratings. So if we are not there yet, please reply and let me help more. If you're not pleased, let me know because rating bad does not result in a refund, there are better options. Rating now will not close this post nor prevent replying. Thanks Chris

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Customer reply replied 7 months ago
Changed the fuel pump out, pressure is still jumping all over the place and check eng light still flashing crusing down the road.So far I've changed
Fuel pump & filter
Plugs & wires
Pressure regular & vac line to it
Chevy Mechanic: Chris (aka-Moose), Technician replied 7 months ago

You are running out of things to blame for incorrect fuel pressure. Have you monitored the pumps power and ground supply to confirm they are staying consistent and no resistance on the ground?

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Customer reply replied 7 months ago
checked that along with swapped the relay with another one,
Chevy Mechanic: Chris (aka-Moose), Technician replied 7 months ago

The only thing I can think of left would be to try another fuel pressure regulator.

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Customer reply replied 7 months ago
OK I just ran across the street to advanced auto, got a new regulator and still the same jumping pressure reading and flashing light when driving. ��
Chevy Mechanic: Chris (aka-Moose), Technician replied 7 months ago

It may come down to using aftermarket parts instead of OEM. There is nothing else left to control fuel pressure than the things we have discussed.

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Customer reply replied 7 months ago
Woukd a vac leak cause the pressure to jump around?
Chevy Mechanic: Chris (aka-Moose), Technician replied 7 months ago

If you had a vacuum leak you should be getting lean codes from air getting into the engine that has not been metered. It is worth checking though.

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Chevy Mechanic: Chris (aka-Moose), Technician replied 7 months ago

Hello, Chris here again,

I am checking in to make sure you got everything you expected from my answer. The option to rate my response or reply is still available. I want to make sure you were pleased with what you paid for.

Thanks Chris

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