Code PO300 – Check Engine Light Coming On
Reader Question
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 uns 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.
Hi there,
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.
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.
Blessings,
Austin Davis
Category: Check Engine Lights
About the Author (Author Profile)
Austin Davis is a consumer car repair advocate. "I just like helping people with their car repair problems". I hope this site was helpful to you. Please like me on Facebook and leave a comment or a review of my site. Google+Subscribe
If you enjoyed this article, subscribe to receive more just like it.
Yes that is a misfire code but the tech should have also looked and found out what cylinder or cylinders were misfiring to help narrow the search down for the fault it could be a bad injector bad coil or coil wire fouled plug coolant leaks from head gaskets or intake gaskets fuel pump not suppling enough fuel pressure causing multiple cylinders to miss under load could be water in the fuel rail or rust or dirt. Maybe its the MAS air flow sensor is faulty or just dirty and needs to be cleaned when the plugs were changed did they all look the same or were some white signs of coolant leaks or maybe there is a injector sticking on how is the exhaust back pressure is the converters or mufflers plugged the possibilities are endless without more information. The diagnosis skills of your local dealership or a trained trusted tech are required on this one for sure but if you had stated the year make model and mileage I could have narrowed the search a bit. Bet of luck
If your vehicle used Dexcool coolant, it could eat away at the intake gaskets resulting in coolant leaking into the cylinders causing multiple misfire code. This happened on my 99 Silhouette. Had to get an intake reseal job ($1300) and then found out about the class action about it (http://www.dexcoolsettlement.com/). It may not be the issue here but is one potential cause of the symptoms, especially if you are losing a bit of coolant over time and/or smell a little coolant when under the hood.
I think timing chain is a red herring. GO somewhere else for a second opinion, GM dealer would know about the dexcool issues and should have seen their share.