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Category: Chevy
Satisfied Customers: 26083
Experience:  ASE certified tech ADVANCED LEVEL SPECIALIST. Wisconsin certified emissions state inspector
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Multiple cylinder missfire P0300, 02 silverado, plugs and

Customer Question

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: 6 months ago.
Category: Chevy
Expert:  AMEDEE replied 6 months ago.

Hello and welcome!

My name isCustomerand I can assist you with your question.

Expert:  AMEDEE replied 6 months 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!

Customer: replied 6 months ago.
Expert:  AMEDEE replied 6 months ago.

And the VIN?

Customer: replied 6 months ago.
Expert:  AMEDEE replied 6 months ago.

Thank you for the vin!

One minute while I pull up your vehicle.

Expert:  AMEDEE replied 6 months ago.

Can you feel the engine misfire?

Customer: replied 6 months ago.
Expert:  AMEDEE replied 6 months ago.

At what engine rpm's?

Expert:  AMEDEE replied 6 months 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.

Expert:  AMEDEE replied 6 months 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.

Customer: replied 6 months 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
Expert:  AMEDEE replied 6 months ago.

Thank you for that information.

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

Customer: replied 6 months ago.
MAF has been cleaned
Expert:  AMEDEE replied 6 months 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.

Expert:  AMEDEE replied 6 months ago.


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!