2003 SS Running Rough PO300 Error Message
 

Hi, I'm a new member. Just bought my 2003 SS about 5 weeks ago. Love her, but she is having some problems I need help with.. I took her on a short trip (against wifes wishes with wife in car-see how this is going?) and halfway to the destination she started to sputter. The check engine light flashed and we pulled over.

I borrowed a reader from a oil change place and saw she was misfiring on multiple cyl. I changed the plugs and wires at their shop. It didn't fix the problem. I had to have her towed home and rent a car to finish my weekend trip.

So can anyone help me with some other ideas of what I can work on when I get home?!?! Thanks in advance (Really wish this wasn't my first post!)

Yhanks in advance

Without more data here are some starting points.

CTS
MAF
MAP
CMP
CKP
FPR
Fuel pressure
clogged exhaust
burnt valves

Thanks for the starting points. I also didn't mention the oil pressure gauge is moving when I rev the engine.

OIl gauge moving is normal. As long as you have at least 20psi at idle and no more than 60 at WOT. You may try finding out if it is a fuel or ignition issue causing the misfire.

Welcome to the forum. Just as an FYI, if you used BOSCH plugs, I recommend changing them again (BOSCH plugs are junk in GM v6's, Delcos are best).

You have a multiple cylinder misfire. Any idea which cylinders? If it's two cylinders, could be a coil pack, see if they share the same pack.

Otherwise, you're at air and fuel delivery. Make sure the air and fuel filters are new. After that, it may be best to check the fuel pressure. If you're not getting enough pressure, that can cause issues.

I had the same issue with my 2003 Monte about 4 weeks after I bought it. I spent about a month trying to figure it out. Turned out that someone had changes out eh intake manifold gaskets before I bought the car and stripped out the rocker arm bolt holes. Here is the thread form when I had my issue...

https://montecarloforum.com/forum/he...-13/cat-29239/

How did they strip the rocker bolt holes doing LIM gaskets? You don't even have to pull the valve covers off.

He has a 3400 powered Monte, not the 3800. When changing LIM gaskets on a GM 3100/3400, the valve cover attaches to the head and the LIM. Also, to get the LIM gasket out and the new one in, you need to remove the rockers and push rods.

A bit more involved then the GM 3800. And I remember mairj40's issue. That was just an odd ball situation. The last guy to mess with his ride must have cross threaded something or who knows....

I'd start with the simple things, plug wires, plugs, if no luck there then your Crankshaft Position Sensor, if no luck after that I would look at your injector drivers and your coil packs.

Got home today and started to trouble shoot the Monte. Looks like the 2nd coil pack is not having spark. I have the coil pack on order. Thanks all who gave advice. Hoping this will fix the problem. I will post results when I get it installed. Thanks again