First off I have a 2000 Z-28 M6. My problem all started out of the blue. I had been raining on my car all day, i started it up and took off from work. About a mile from work my car started running rough, real rough. To the point where i could only go about 25 mph. My SES light started flashing on and off rapidly. Lucky my grandparents house was near by and I have an extra car there. I took it there until I could work on it. The next day I barrowed a Code Reader from work and got 2 codes, the first was that on the left bank, the upstream o2 sensor had high voltage, the second was the downstream sensor had low voltage. I cleared them and started the car back up. The car was still idling rough. Then the SES light came on and i got another code, this one was totally different from before. It was random cylinder misfire. After work, me and a coworker went to work on it somemore. I bought a spark tester from work and i had a code reader with me. We went and the first thing we did was clear the code. THen we started the car up. Still running rough. We checked all the wires with the tester and they all had spark. Another code came up, cylinder 1 misfire. We cleared that and went to drive it. The car ran well until a couple of blocks away and it started running rough again. We kept the car running and pulled over, my coworker went and checked the spark while i checked the code. THe code again was random multiply cylinder misfire. Then i cleared the code and sat there for a couple of minutes. I put the car into first gear and took off, she ran fine. I took the car back to my grandparents house for the night. The next day i drove the car to work, at first the car ran rough, then i sat at a stop light and then she ran fine. At work i took out #1 and #3 plugs (easiest to get to) and they looked fine, except that 3 had a chip in it. So I drove the car for about a week without changing the plugs, (had to fine time). The car would run fine then right when i start it up, it would run rough. I changed the plugs, I put 41-985 iridium delcos in, but what i took out wasnt. THey were 41-952, which delco doesnt make nemore. They changed it to a 41-932. So i thought that was the problem in the begining. So after I spent 2 hours changing my plugs, i took my car out for a drive. She ran better then she did when i first got her. I thought that i solved my problem, negative. I let her sit for a couple of hours and unitl i had to go back into town. I let her warm up for about 3 minutes, during that time, the car started misfireing again, this time worse then before, and again the SES light was flashing on and off like the first time. I turned the car off, then right back on, and she was fine. The next day i drove it to school, it ran fine. THen after school, i went to the mall, when i went to leave the mall, the car felt like it was missing half the cylinders. I could hardly accelerate. It got so bad, that when i pressed the gas, the car almost died on me. Luckily my grandparents house wasnt far. SO i turned off the car, then back on, and she was fine. I have ran out of ideas on what it could be. Some people said it could be the coils, plugs, injectors, or maybe the fuel pump. The plugs are out of the question, and maybe the coils. If any of you have ne ideas on what it could be, please let me know. Cause i have no idea.

 

Did any water get in the PCM ?? Take it out and check the terminals for corrosion.

 

if u got codes for bad o2's then u shouldnt have ignored it. o2's will definately cause a misfire condition and if u had more then 1 o2 go bad then this sounds like a probably cause. if ur worried about fuel then get a pressure guage for the rail and hook it up and see what its running at. but i would doubt u have a fuel delivery problem. check o2's, thats a huge factor.

 

im having this exact same problem....raining all day....same thing man. im gonna change out the first bank o2 and see what happens. i also have the random misfire and times the car barely wants to move and others it feels fine. at lights is when i find it messing up and wanting to die.

 

hahah just saw that this is a pretty old post!

 

Its cool man, ,I was just reading this post also and I was having the same issue. Rained cats and dogs and my car started to misfire. Changed the o2 sensors and it was fine for awhile then started again. I first thought I needed a tune because I just installed longtubes. But still did it, changed plugs and wires and it seems fine untill the car goes on a 10-15 minute trip then it misfires again. I'm also getting a ticking sound also so I'm thinking maybe an exhaust leak. But can an exhaust leak cause misfire?

 

If this problem is happening after the car goes into closed loop it might be an air leak in the intake tract. Had the same problem with my vette, said it was a bad o2, turned out to be a leak in the intake.

 

Ouch. That sucks. Minus the ticking sound, My story is the same as scof0elife... I was just getting ready to order some O2s online...

I put on a new intake too... Man, I don't want it to be an intake leak... That would be a bitch!

Now I dont know what to do.

 

I know man, what to do what to do

 

just did longtubes+full exhaust, and plugs+wires, and my egr is leaking...and im getting the random misfire thing, and a low idle go up and down from ~700 down to 500 at stop lights...is this just the egr or could it be the o2 sensor...check engine light is on with codes;P0300,P0160,and P0140

 

Don't know...

Man, I don't want to take off my intake! Someone wave a magic want and fix my problem please.

 

Did you ever figure this out? Im having this same problem over HERE in this thread.

 

You know, I got to thinking about it. If it is unmetered air coming in through the intake tract (I did put on an LS6 intake...), then if I swap the bank 1 and bank 2 sensors around (it only says bank 1 is bad), then that should tell me if it's really bad or not. Duh.

 

I fixed this problem on mine last night, turned out just to be the stocker o2 sensor that I hadnt replaced yet.