Hello, my vehicle is having issues. It threw a po300 code. Brought it into a local shop that I have dealt with for years and they ran diagnostics and came up with that code. After the diagnostic, I was told that the only thing that would cause it was the timing chain since all the electronics checked out. Previously I replaced the plugs,wires cap,rotor,fuel filter,air filter.
I had a friend replace the timing chain who is a retired gm mechanic.(He is not up to date on the computer stuff, but understands them somewhat). It does it most when you are driving on a flat surface or going down a slight incline when the engine isn’t under load.
It runs extremely bad when it is raining or damp outside. I also ran two tanks of fuel with Seafoam in them.It was doing this before replacing the parts listed.(Also replaced the camshaft position sensor).
I am not one who likes throwing parts at it. Could not find any vacuum leaks. It starts fine and seems to idle fine. I am at a loss of what else it could be. I’ve even looked at it in pitch black to see if I see any arcing and squirted some water around to see if it starts running rough to no avail. It has the vortech 4.3 V6 w/csefi. Thanks for your time.
That code is for multiple misfire issues, like spark plug wires etc. etc. so I would still be suspect of them. if you did not have this issue prior to the timing chain replacement…I would be highly suspect of a problem with its installation.
You can install a timing belt or chain incorrectly, but the engine will still start and run but you will have a loss of power issue, poor fuel mileage, check engine light on, rough idle speed and hard to start problems…but it will run.
We refer to this type of installation as “off a tooth” since the metal gears and the timing chain or belt are physically off just one tooth on the gear, causing the engine to be “out of time”.
Would be nice to have a qualified dealership mechanic at least diagnose this problem, anyone can repair it once you know for sure what the problem is. Might be worth a $100 check out charge at your dealership before you spend more money on this.
Sorry wish I could be more of assistance to you, but need more information to go farther.
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