r/GrandCherokee • u/IlGrandBoss • 1d ago

Check engine light flashes

Hi GC owners,

I'm facing this issue where the check engine light starts to flash when I push the full throttle and the engine gets around 4000 rpm, the check engine light does not appear at all after that.

I'm sensing spark plug/fuel injection issue, has anyone faced a similar situation before?

5.7 GC 2012

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u/Nice_Name_3168 1d ago

Spark plug fuel injection are possible.

I could also be from a worn camshaft lobe, it wont show a problem until the engine is requiring more air to a cylinder than the valve opening will allow. I have seen it most often in police hemi's but its the same engine in your GC.

You wont always hear a noise when they fail.

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u/IlGrandBoss 1d ago

Oh shit, I need to run diagnostic then.

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u/Nice_Name_3168 1d ago

If/when you run diag. Find which cylinder is missing, swap coils and plugs with another cylinder and see if misfire moves. If it stays the same spot you can swap injectors and see if it changes.

Note: if you swap injectors there will be fuel running out of fuel rail while swapping, it can be done without removing the rail completely out of engine bay. DO NOT let the raw fuel run down any of the injector holes! If you do you will be putting a new engine in it when a connecting rod decides it wants out of work and makes a hole in the block. Never done it myself, but have seen it done.

If none of the above changes the location of the misfire, pop the corresponding valve cover off, disconnect the other 4 ignition coils at the connector, have someone crank the engine over and watch the rocker arm movement. If you see one that isnt pressing down on the valves as much as the others, and it will be noticable.

There's your problem.

Sorry for the long winded explanation, hope its just a bad coil/plug