Yesterday I was just doing some routine maintenance oil change, air filter,etc. Then went to go wash my car and on the way back it starts acting up and SES light starts flashing. Checked the code and it is a PO300 multiple/random cylinder misfire detected. I have no idea what it could be, car ran fine on the way to the carwash, so either I got water on something i wasnt supposed to, or I also hit a pretty narly pothole on the way out so i could have jarred something loose, or something just decided to go out, i have no idea I didn't wash the engine/undercarriage anything like that just the outside of the car. Where would be a good place to start? what causes this?

 

You probably got the optispark wet somehow. Since your car has a vented optispark it should dry out and be fine.

 

I washed it yesterday afternoon and its still doing the same thing today, plus I've washed it a hundred times that same way and never had this happen before.

 

Start checking plugs and wires.

 

you have cps sensor check the wiring mine did the same thing. Ok heres the deal I have longtube headers it burned the wires coming down thw side because there so close. you have to get the wire routed away. if its not your cps wires or those wires on the side of the firewall its your opti..... what kind of headers are they I can guarntee you its the wires on the passenger side theres 8 one is to your cps i bet thats getting wet mine did the same thing i even bought a new cps sensor and harness still did it till I found the problem.....

 

My headers are pacesetter shorties and pacesetter off road y. both have ceramic coating. This is probably a dumb question, but where is the cps? How did you stop your wires from getting wet?

 

My 96 SS keeps giving me the P0300 code and it runs fine and I can't find what is causing the code to pop up. I have new MSD wires, replaced some EVAP stuff, new AIR check valves, new headers, new O2's, new cats. I've read it could be an ICM problem, ECM problem, injector problem, Opti problem. My car seems to run perfectly fine so I'm gonna keep an eye on it but not spend any more trying to solve it.

 

wish i could say the same, but my car is running like hell so I really need to fix it.

 

While it's dark, start it up, raise the hood and look for sparks around the wires.

 

Went out and fired it up, saw sparks right around the spark plug area, in a circular pattern. Pretty much a constant lit up circle that varied in brightness right around where the wires met the plugs. I noticed it on the second cylinder from the front, third cylinder from the back, on both sides. I dont know what cylinder #'s those are. There is also a noise present that wasn't there before from the sparks.

 

I think it is cylinders #4,and #3, correct me if im wrong

 

You've got a misfire. If the noise is a click/tic like noise, it's bad connection to the plug. Time to check condition of wires and plugs on those cylinders, and be sure the wires are securely snapped onto the plugs, and the plugs are tight.

Cylinders are numbered like this:

Driver's side are odd numbers, from front to rear: 1,3,5,7
Passenger side are even numbers, from front to rear: 2,4,6,8

 

What knid of plugs and wires are you running. Ive hade trouble with bosch platinums in the past so i went with NGK's and that solved my mifire problem. Also check you wire routing and make sure none of them are burnt or cut by the belt.

 

Guess I'll spend my weekend putting on new plugs and wires. I have bosch platinums as well and they haven't been changed since i put my headers in at least 4 years ago so it is a task that is well overdue. The wires are just some generic ones that were on it when i bought the car so it couldn't hurt to change those as well. I think im going to go with the NGK plugs, does anybody have any recomendations for wires? Any tips that would be helpful for changing the plugs and wires would also be appreciated.

 

Also, do you think i should replace the coil, coil wire or anything else while im down there?