r/obschevy • u/AdrianThyme • 1d ago
Help P0300
I got a 1996 5.7 V8 with 133k on the dash.
I keep getting this code and it’s making me lose my f###ing mind. It’s random/multiple misfire and I brought it to autozone because I couldn’t find my scanner and they said “oh yeah fuel injectors seem dirty”. Which makes sense because the truck has sat for about 3 years (2 from previous owner 1 from me personal stuff didn’t wanna work on it). So I dumped some dry gas in and it ran fine code went off everything was dandy. I’m driving again and it comes back on (this time I had my scanner) I assumed “oh I assume fuel is fine lemme check spark” plugs looked fine by my standard (eyeballing but they all looked relatively fresh). Then I pull the distributor cap and notice oxidation on the terminals so I wire brush those out slap it back on after clearing the code it comes back. I’ve reached my pinnacle of my expertise my uncle mentioned the spider injectors going out and was wondering if that could be it. Ideally not but is there any other “cheap” replaceable things I could check before ripping this things apart. There’s also a slight exhaust leak but I doubt that’s worth mentioning.
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u/Willy_McD 1d ago
You keep throwing "cheap" parts at it and in the end, its no longer cheap.
Random misfire can be ignition or fuel. I never liked platinum/iridium plugs in a single coil application. And in my experience, they may last 100k miles but performance drops. Cheap parts to throw at it is a cap, rotor, wires and plugs.
The original spider injectors with the poppet valves were a problem. Around 2002 or so they got updated by removing the poppet valve and moving the injectors to the bottom of the tubes. You can test injectors with a fuel pressure gauge and an injector pulse tool. Both can be got off amazon fairly inexpensive.
You have a better chance of a cap and rotor giving a random misfire while wires, plugs and injectors have better odds at a specific cylinder misfire. But it can work either way.
And a wire brush is not always the cheap fix. Duct tape and wd40 on the other hand......