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Multiple cylinder missfire P0300, 02 silverado, plugs and

Customer Question
multiple cylinder missfire P0300 JA: What...
multiple cylinder missfire P0300
JA: What is the model/year of your Chevy?
Customer: 02 silverado
JA: Are you fixing your Silverado yourself? What have you tried so far?
Customer: plugs and wires have been replaced, did the fuel pump a little while ago. just tested all coils today.. seem to be fine
JA: Have you ever replaced the fuel pump, or is this the original?
Customer: fuel pump is replaced ^^
JA: Anything else you want the mechanic to know before I connect you?
Customer: my evap system test failed. Emission leak.
Submitted: 1 year ago.Category: Chevy
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Answered in 20 minutes by:
1/3/2017
Chevy Mechanic: AMEDEE, CHEVY TECHNICIAN replied 1 year ago
AMEDEE
AMEDEE, CHEVY TECHNICIAN
Category: Chevy
Satisfied Customers: 27,086
Experience: ASE certified tech ADVANCED LEVEL SPECIALIST. Wisconsin certified emissions state inspector
Verified

Hello and welcome!

My name isCustomerand I can assist you with your question.

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Chevy Mechanic: AMEDEE, CHEVY TECHNICIAN replied 1 year ago

I will try my best to answer all of your questions.

However, before we get started, please let me mention a few things.

1. If at any point you would like to speak on the phone, please feel free to request a phone call on your end and I can call you right away.

2. If you dont understand any technical terms or anything that I mention (component tests or theory or operation), please let me know and I will provide you with a more in debt explanation or answer.

3. Please understand that I am here to help you anyway I can.

Can you feel the engine misfire? If so, what rpm's does it misfire at?

Can I start by getting the codes in the computer and the VIN?

Thank you!

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Customer reply replied 1 year ago
P0300
Chevy Mechanic: AMEDEE, CHEVY TECHNICIAN replied 1 year ago

And the VIN?

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Customer reply replied 1 year ago
2GCEK19T421161848
Chevy Mechanic: AMEDEE, CHEVY TECHNICIAN replied 1 year ago

Thank you for the vin!

One minute while I pull up your vehicle.

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Chevy Mechanic: AMEDEE, CHEVY TECHNICIAN replied 1 year ago

Can you feel the engine misfire?

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Chevy Mechanic: AMEDEE, CHEVY TECHNICIAN replied 1 year ago

At what engine rpm's?

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Chevy Mechanic: AMEDEE, CHEVY TECHNICIAN replied 1 year ago

The most common cause of a P0300 random cylinder misfire condition on this engine are the following..

Faulty secondary ignition components..
dirty MAF sensor
leaky intake manifold gaskets
Plugged or restricted Fuel injectors

If these things have been done and or verfied as OK or good, then the next most likley possible cause would be to do a crankshaft position sensor variation re learn procedure.

Here is the relearn procedure..

Crankshaft Position System Variation Learn

Block the drive wheels.
Apply the vehicles parking brake.
Cycle the ignition from OFF to ON.
Apply and hold the brake pedal.
Start and idle the engine.
Turn OFF the A/C.
Place the vehicle's transmission in Park (A/T) or Neutral (M/T).

Important: While the learn procedure is in progress, release the throttle immediately when the engine starts to decelerate. The engine control is returned to the operator and the engine responds to throttle position after the learn procedure is complete.

Slowly increase the engine speed to the RPM that you observed.
Immediately release the throttle when fuel cut-off is reached.

With a scan tool, enure that it displays in Learn Status: Learned this ignition. Now the procedure is completed successfully.

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Chevy Mechanic: AMEDEE, CHEVY TECHNICIAN replied 1 year ago

I am glad I can help!

It has been a pleasure working with you. Please dont forget to honor your good faith deposit by rating my answer as "5 STAR SERVICE" for assisting you today.

Keep in mind, we can still continue this conversation at no further cost to you even after you rate my answer. Just reply back to me using this page and I will get it and get back to you ASAP!

Also, if you are a member or if you have a subscription to the site, you still need to rate my answer in order for me to get credit for assisting you with your question.

Please let me know if you have any further questions.

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Customer reply replied 1 year ago
It backfires a little bit at about 1500- 2000 rpm, cant really feel it then jst hear it. You can feel it and the CEL will flash sometimes while excelerating and mostly only at highway speeds. 80-120 km/h. It just seems to hav a little bit of a rough idol, an inconsistent exhaust flow with a lot of emission. Very bad fuel mileage. While driving around town. Cant handle highway speeds for some reason unless you hit the gas just right it wont miss
Chevy Mechanic: AMEDEE, CHEVY TECHNICIAN replied 1 year ago

Thank you for that information.

Were all of those things done/replaced that I mentioned above?

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Customer reply replied 1 year ago
MAF has been cleaned
Chevy Mechanic: AMEDEE, CHEVY TECHNICIAN replied 1 year ago

Ok, then that leaves the other things I mentioned above.

Glad I can help! Please dont forget to honor your good faith deposit by rating my answer as "5 STAR SERVICE" for assisting you today.

You should see the rating system towards the top of the page.

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Chevy Mechanic: AMEDEE, CHEVY TECHNICIAN replied 1 year ago

Hello!

It'sCustomerfrom just answer.

I am just checking in to see how things turned out and if you need further assistance.

Please let me know!

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AMEDEE
AMEDEE
AMEDEE, CHEVY TECHNICIAN
Category: Chevy
Satisfied Customers: 27,086
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Experience: ASE certified tech ADVANCED LEVEL SPECIALIST. Wisconsin certified emissions state inspector

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