ok so the story goes like this, I filled my tank on my 96 LT1 up on sunday, drove around 50 miles without a problem, parked it till this morning. This morning i started it up and it would not idle properly as well as it would stumble at all RPM ranges and hesitate really badly. It threw some codes and the check engine light was actually flashing during part of it. I have the following codes, P0131, P0300, and P0303.

P0131 - O2 sensor circuit low voltage (bank 1, sensor 1)
P0300 - Random/multiple cylinder misfire detected
P0303 - Cylinder 3 Misfire Detected

the P0303 only shows up when it happened (i have a logger that stores the codes as the occur). the other 2 show up every time the car starts.

Now I replaced that O2 sensor back in march with a new AC delco unit cause it was doing a similar things, it would not idle correctly although it didnt miss or hesitate. I was thinking it was the opti, as my car has 90k on the original opti but nothing is leaking and it didnt get wet. What bothers me is that it was running perfectly fine when i shut it off on sunday and now it runs horrible. I was thinking that I got some gas with water which would make sense cause it was hesitating like it was starving for fuel so i put in some dry-gas and now the miss and hesitation seems to be gone but that O2 sensor is now not working.

I can visually see my driver side exhaust putting out more "smoke" than the passenger which would make sense as that O2 sensor controls the air/fuel ratio and that bank would be running really rich.

Would bad gas cause a misfire enough to ruin a O2 sensor? why does this side seem to keep destroying them and i replaced the other side a year ago and it is still fine.

I have only driven about 20 miles since i added the drygas and i have not been able to get it to hesitate again which makes me think it was bad gas

sorry about the long post but this whole thing is really weird as one day it is fine and it sat for 2 days and it runs like crap

thanks

 

This might sound a little silly, but there could be water in the fuel. I had this problem once with a tank of gas...the water will settle to the bottom of the tank as it seperates from the gas. I have a fuel fressure guage with a bleeder hose on it (about $40). I bled some of the fuel out and let it settle for an hour and found that the water had settled to the bottom of the jar.

 

that is what i was thinking and that is why i bought the drygas...it seems to run much better after that, but would that misfire be enough to destroy an O2 sensor?

 

I don't think you were putting enough water throught he system to cause an O2 sensor to go "bad". I've had bad fuel 3 time and had to bleed a couple of gallons each time to make sure I got all of the water out, and I have never had to replace an O2 sensor. Not sure what's causing them to go bad.

 

anyone got any ideas about the 02 sensor?

 

Did you check your voltage alt?
See if the charging system is up to par.
You need to check the vaccum in the engine and see if the cat on the one side might be clogged.
Put your hand at the back of the exaust and have someone rev up the engine.
See it it blows your hand away on both sides.
Engine should have 14 inches of vaccum.

 

voltage seems to be good, it does put out 14.4 volts, i can bring it to be tested if need be...as for the exhaust, at idle they both seem to flow similar out the back, i will need to get a friend to rev it for me

just curious, why would a bad alternator cause o2 sensors to die?

 

it still is not running perfectly smooth, but i had another cylinder 3 misfire detected this morning.

what does this sound like? a fouled plug? opti? anyone?

 

Well I would be looking at the plug to see whats up.Mabey a wire?

 

just got home so i am going to let it cool and i will pull that plug and see how bad it looks

 

Check Your A/f Ratio, If You Can. A Rich Running Car Will Kill An O2 Quickly. When The Car Misses, That Is Raw Fuel Going Into Your Exhaust. That Will Kill O2's And Cat's. I Would Absolutly Check Plugs And See If They Are Fouled. Also, If You Have Water Settled In Your Tank And It Makes Its Way Into The Combustion Chamber And Into Your Exhaust, It Will Kill The O2. Mabye You Should Try Draining Your Tank, Just To Be Safe. Good Luck And I Hope You Find This Info Usefull.

 

i pulled the plug and it was covered in carbon, which is what i expected...i cleaned it/regapped it and put it back in. it seemed to run a little better but im sure that it will get refowled up fairly soon as i can smell it running really rich.

what is the best way to drain my gas tank? should i siphon it out?

 

Your alt should drop back into the 13 volt area if the battery is good.
How many miles do you have on the car?
You have 3 O2 sensors check the wires under the car and see if the wires going to them are not burnt or conectoin good.
Remember a rich condtion is a lean motor.
Does your cruise control work?

Best way to remove the gas is to remove the gas door lid and all 10 bolts and suck it out that way.
If the battery is good you can remove the schrader valve screw on the fuel rail install a threaded 6 an line and turn the key on.

 

I had the same problem with a misfire. Turned off the lights and had a look at the plugs and wires and sure enough, I had a wire that was lighting up. Moved the wire with a zip tie, cleared the code and the problem was solved.

 

the battery and alt are good
there are 4 O2 sensors, but i will not be able to check them all until tonight, but i know one does not work (B1, S1) as i am logging its voltage and it stays pretty much between 0-.1 volts and sometimes comes back online and then returne to almost always that low of a voltage. The cruise control does work. I am probably going to get all the fuel out, change the O2 sensor that does not work properly and clean the plugs tonight...hopefully that will cure this problem

i am a little confused on what you said a rich condition was a lean motor, but it is running too rich which is too much fuel, which would leave lots of carbon in the combustion chamber (it did on the cylinder that keeps misfiring). If it was too lean it would be running very hot and that spark plug would not have been covered in carbon. how is a rich condition a lean motor?

 

If the o2 sensors read a lean condition they will tell the computer to richen the motor.
I would also check for vaccum leaks.

 

From now on, post what year vette you are talking about.