Jump to content

04 Sierra P0300


Recommended Posts

Does anyone have any advice where to start looking for a P0300?

 

Truck has LM7 with 188k on the clock. Runs fine until it starts to warm up or going up a grade and starts missing and spitting. Things I've replaced over the last year,  throttle body, maf, map, cats and all o2 sensors, plugs and wires. Replaced coils 2 years ago. Fuel pump was just replaced with a delphi, check engine light would go on and it would spit and sputter, wouldn't start one day so changed the pump and it started but still spits and sputters when its under a heavy load.

 

Haven't changed the cam or crank position sensor, pedal assembly, intake gaskets or injectors.

 

Its giving me a flashing p0300 when going uphill but them it turns off when I'm back on level ground and no extra stress is on the motor. Passed smog like a champ 4 months ago. No clue what could be going on.

Link to comment
Share on other sites

Get a live data scan tool on the truck to see exactly what cylinder(s) are misfiring. That will make it far easier to track down what to look at.

 

It could be just one cylinder or an entire bank of cylinders but it's hard to say right now.

Link to comment
Share on other sites

On 9/20/2020 at 7:30 PM, CamGTP said:

Get a live data scan tool on the truck to see exactly what cylinder(s) are misfiring. That will make it far easier to track down what to look at.

 

It could be just one cylinder or an entire bank of cylinders but it's hard to say right now.

+1 

Link to comment
Share on other sites

Misfire counter shows its all over. Sometimes it doesn't start and takes 2 or 3 tries to get it going. Also I noticed the Delphi pump I pump in it has a working pressure of 54psi and the spec on these trucks is 55 to 62. Could that be a possible culprit? I checked pressure while the line was primed and am only get about 50psi. Maybe a bad pump?

Link to comment
Share on other sites

Join the conversation

You can post now and register later. If you have an account, sign in now to post with your account.

Guest
Reply to this topic...

×   Pasted as rich text.   Paste as plain text instead

  Only 75 emoji are allowed.

×   Your link has been automatically embedded.   Display as a link instead

×   Your previous content has been restored.   Clear editor

×   You cannot paste images directly. Upload or insert images from URL.



×
×
  • Create New...

Important Information

By using this site, you agree to our Terms of Use.