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P0300 after repairs


Topic starter

2013 Cadillac Escalade ESV 6.2l

I had a lifter collapse, did a lifter job had the heads done put back together runs great as you drive but when you get to a red light or stop sign I get a missfire on cylinder #4, not all the time but a check engine light with code po300 pops up then when you start to drive it goes away on its own. New plugs, wires, swap coils new fule injectors and I also swapped fule injectors no change, I went back to the dod or afm I did not do the delete on the dod or afm

5 Answers
Posted by: @graycady

number 4 is the only one that don't make a difference

that just means it's misfiring. You still don't know why. If there's no spark, then of course turning off the fuel won't make a difference, right?

It might be a clogged injector, but it could also be a bad spark plug, bad coil, no compression etc.

The way you test things is by process of elimination.

so swap the injector with another cylinder and see what happens

swap plugs, coils, etc.

We have a whole article dedicated to troubleshooting misfire in the FAQ on our front page.


Cylinder 4 & 6 are neighbors so hopefully you don't have a failed head gasket between them.


problems that show up at idle, but not at speed are also related to vacuum leaks, so it could bad intake gasket as well, which a smoke test would reveal.


p0300 is a random misfire, which could be more than just cyl #4. I would use your diagnostic tool to get an actual misfire count for each cylinder.


bad lifters usually ruin the camshaft, so the engine may never run right.

Topic starter

Only misfires on 4 and 6. 6 starts a while after 4 misfires. I used the scanner tool to shut off each fule injector one by one number 4 is the only one that don't make a difference in idle when it's shut off, so I'm thinking maybe bad fule injector??? I'm getting power to all the wires to the fule injectors. Thoughts?

Topic starter

Ok changed fuel injectors, Cadillac started but real rough idle I pushed on the gas and it smoothed out a little let off the throttle and it died, I tried to start it back up and it just cranked and cranked I did that three times no start. On the fuel rail I relieved pressure but there was no pressure I don't believe there is a fuel filter I think there's a fuel strainer on the pump so I got to drop the tank, does that sound like the culprit for the problems I've been having this whole time after the lifter job? Camshaft looked good still throwing code p0300 and stable track code comes up on the dash just didn't know if a clogged strainer or if my pump was going out I have not checked fuses yet and I did not have somebody there with me to turn the key to see if the pump turned on I'm doing that later today. Also put new plugs wires and coils on I'm getting spark on all cylinders I put the snap on scanner on to see which cylinders it was four and two

This post was modified 5 days ago 2 times by graycady

well you're ignoring all of my suggestions and throwing parts at the problem instead of diagnosing, so you're going to end up poor and none wiser. I gave you all the advice you need. Measure your fuel pressure. Good luck.

Topic starter

I have been trying your suggestions checked fule pressure Put a new timing chain, gears, chain, camshaft, bearings camshaft position sensor all the 2nd time I took it apart to get the heads refurbished so had to get new gaskets, nothing changed ran just the same, still misfiring on cylinder 4 then the code po300 pops up then I start getting missfire on cylinder 6 sometimes it goes away on 6 and moves to cylinder 2, I have swapped coils plugs and wires and injectors and nothing changes consecutively with what I'm changing, some times 8 6 2 and 5 are all missfireing after number 4 starts missfireing after the code 300 comes up number 4 hits around 150 to 170 misfires before any other misfires start and the misfires on all the other cylinders misfires 2 -12 times in that cycle nothing

This post was modified 3 days ago by graycady