Well, let me start by saying that i have searched and read almost every misfire topic that was posted and have a fairly good idea what i need to do, but i have a few questions that are specific to my situation. I have an auto scanner OBDII and it gave code P0300-random/multiple cylinder misfire.

- It has an exhaust leak somewhere, sounds like crap. i have located where the previous owner had, and this will sound stupid, used a cut beer can and electrical tape to try and repair the exhaust pipe. the holes are appox, 10 inches past the cat converter. here are some pics of where the beer can was and the holes.....





So, the symptoms of the car are like, rough idle, (also to note, the guage reads 1000 rpm at idle, while the scanner is showing just approx 795 at idle and the same while accelerating the guage and scanner vary about 2-300 rpms. So could that be a problem? And while in gear, it feels like i am driving in 1st gear while using 3rd or 4th gear, it will accelerate but it is real sluggish if pressed hard on the gas pedal, if i let off, the exhaust note calms down and it accelerates a little better, but still feels like a 4 cylinder at best.

I have not checked the plugs/wires/coil in detail yet because the previous owner said he just replaced them with platinum wires and plugs. given the condition and quailty of the "repair" of the exhaust, i will double check his work. I am underneath the car now doing the exhaust repairs at the moment because even if it is not a direct connection to the misfire, it still needs attention.

So, should i cut out that part of the pipe and replace it because it is dented in, possibly causing restriction? or just repair it with the kit at autozone?

This is a 1997 3.8L V6 with manual transmission. If you need more info, just let me know. I have a scanner and multimeter to help troubleshoot further, and the haynes repair manual. I don't have or know how to use a timing light or do anything with fuel injectors, seems to advanced for me!

Thanks for any and all help! I am not an expert and am open to all advice! Thanks again!

 

Please let me know if anything looks out of place. Is that how the wires are supposed to lay like that? The plugs look like a real pain to get to! Is it easier/possible to access them from underneath the vehicle? I have a 3 ton hydraulic floor jack and (2x) 2 ton jackstands.Thanks!

 

Here are some videos of the engine running, as well as video of scanner reading and dash. Also, the cat converter sounds like a tin can with rocks in it that you are shaking around. i tried to hold it externally to see if it was loose, but it made no difference in sound. And although you can't see from the video, there was some smoke coming from engine compartment and it smelled like burned oil. i opened the engine cap and smoke was coming from it, not much but small cloud. also the neck that holds the oil fill cap was a little loose. the engine temp was getting hot too, like almost 230 F. Normal stuff? i don't know.

http://tinypic.com/player.php?v=2q3w2v5&s=5

http://tinypic.com/player.php?v=34rydsl&s=5

If you need anymore pics or videos of anything in order to help, just let me know and i'll get it posted. Thanks!

 

The PO300 random misfire code is one of the more vague, broad-based error codes you can get. And even though it says "random/multiple", it still could be only one cylinder with the problem. It can mean bad: plugs, wires, oxy sensor, fuel pressure, fuel injector(s), fuel injector wiring. Flip a coin and pick one!
Let's assume it's not plugs and wires since those were changed by the p.o., probably he was chasing the same problem?
The hole in your exhaust wouldn't have any effect on engine diagnostics, but might as well fix it right anyway. I've done a temporary quick fix with a can like that before, but with hose clamps, not tape. With a crushed pipe, I would cut it out and splice in new.
A good part of your problem might be here where you said "the cat converter sounds like a tin can with rocks in it that you are shaking around..." Bang on the cat with your fist. If it sounds like there are chunks of "something" rattling inside, then your cat is bad. Sometimes the insides of a cat can break apart, and chunks could be facing any which way, which will restrict exhaust flow greatly. I've had it, I've seen it, and even wondered how in the hell did the engine breathe at all. I would check the cat out first. Your whole issue could be with a bad/plugged cat.

 

Your Random misfire does not sound to be your cat you neither have an spark or a fuel problem If any of you coils have any type of build up rust corrison on them they need to be replaced you can not clean them . Same follows your spark plug wires. The way the 3800 motor is installed in the camaro there is not enough air flow to cool the ignition system . I used exhaust header wrap on my plug wires to help keep cool . To check you fuel injectors you can make a very simple led tester light with a bi led from radio shack and resisitor and just soilder wires to it and i used paper clips as my probes cost me 2 dollars comes in handy when testing modules light will change colors as they communicat. As for your spark plugs platium plugs are susposed to be good for 100,000 miles they only last about 30,000 at best in the 3800 i reccomand using stock ac delco . Now as for you exhaust if your o2 sensors are bad they can cause a lean condition and they will not be enough fuel in the cyclinders to fire completely . But is not easily dia without a tech 2 module. Your best bet to slove you misfire is to try to isolate the problem by figureing out what cylinders are misfireing an easy safe way with the motor running at a idle you can unplug your fuel injectors just simply push in on the metal clip and pull. this will not harm your motor any question just ask

 

thanks for all the info! I bought the cat converter today, i am going to cut out the old one and clamp in the new one and use muffler and tailpipe repair putty to seal it more. Is that a good idea or is it necessary to take it to a muffler shop? As for the O2 sensor, how do i test it or how do i know if it is bad?

I also bought wires today and 3 new coil packs, which i will also install tomorrow. I am going to check the fuel filter as well. What am I looking for in the filter to tell if it needs replaced?

Thanks again for the help!

 

You fuel filter should be replaced every 20,000 or so miles when you remove it most of the time the gas will have a rust color this is normal . Make sure you relive the fuel pressure from the line first. Pressure relife valve is located on your fuel rail on the passenger side. As for your cat that could work using the muffler mend most muffler shops will weld it on for 30 or so. Your o2 sensor could be ohmed out but is very unreliable the specs for them normaly range a 500 ohm difference between good and bad. Pcm normallly will kick a R or L bank fuel trim or lean condition when bad.

 

Well, good news is I fixed the misfire problem. It was the front coil pack that was no good. I checked it by removing the wires 1 at a time on all the coil packs. the 1st 2 wires, did not change the engine at all, meaning it didn't try to cut off. the other wires did. so i cleared the code, run it up and down the road, and it ran like a champ. So, I was basically running on 4 cylinders until i corrected it. Made a huge difference!

I changed the fuel filter, replaced the air filter with K&N. could not/lost interest in changing plugs n wires cuz they are a pain to do, even with the car jacked up and going in from underneath. didn't change the cat converter, cuz the O2 sensor is rusted/stuck into it and i cannot free it. it does sound a lot better now though after the misfire was corrected, so maybe it is good after all, i don't know.

Thanks for all your help, I feel the 200 hp now!