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Random Misfire P0300 started today in the RAIN

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Old 11-04-2010, 07:31 PM   #1
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Default Random Misfire P0300 started today in the RAIN

Is it the 02 sensors??? I've mostly been getting P0300. I got a Misfire on Cylinder #1 code, and a P0113 IAT sensor code. P0300 keeps coming up and its running like its only working on 3 or 4 cylinders. Its pretty bad. It's been raining constantly today and the misfire randomly started today. What do you guys think?

Car is 02 Z28
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Old 11-04-2010, 08:39 PM   #2
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any 1?
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Old 11-04-2010, 08:46 PM   #3
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If you have a misfire on Cylinder 1 then I am sure its cylinder 1. You probably have a fouled plug or a bad wire on cylinder 1. Check the wire first and make sure its on securely on the plug and on the coil pack.
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Old 11-04-2010, 08:50 PM   #4
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yeah the cylinder 1 code came on only once. Random Misfire comes on now. I'll check it again right now. Thanks for the advice.
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Old 11-04-2010, 08:51 PM   #5
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I would still check #1 first then if you don't find anything check the others.
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Old 11-04-2010, 09:15 PM   #6
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I just went out to check it/test drive it again. Was running fine for 1 minute then started missing again. I checked the code it random misfire came up again. Just P0300. When I had a 98 Z28 this same problem happened and it turned out to be the 02 sensors. I'll check cylinder 1 tomorrow. Should I try swapping the plug and plug wire to cylinder 2 and see if that code comes up? Fuel injectors are fine.
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Old 11-04-2010, 09:17 PM   #7
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its possible its an O2 sensor but but I would check the cylinder it called out first then if that doesn't fix it then check them all. Yes you could try swapping the plug wire to a different cylinder and see if it the code changes to a different cylinder. How old are the plugs and wires? If they are original then might be as good time as any to just replace them.
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Old 11-04-2010, 09:24 PM   #8
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I just got the car in May. The wires are gray and I believe they are original. Car has 76000 miles. Also, after driving it smells like burnt toast in the engine bay. It almost smells like a burnt clutch. Any ideas?
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Old 11-04-2010, 09:55 PM   #9
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I agree, check the number 1 cylinder first. How bad is the miss? Does it feel like one cylinder, or is it just running like total **** (like a whole bank is missing)?

If you had a way of logging the car, or even a handheld tuner where you could see the O2's mv readings you could easily rule those out. You could however wait till the car cools completely, crank it up and drive it before it warms up and falls into closed loop and see if it misses. If it doesn't miss at first and immediately does after its warm, then there you go. I just got a P0300 code today, because of a bad o2 senser...

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Old 11-04-2010, 10:03 PM   #10
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yeah it runs fine when its cold then goes into miss mode. Feels like a whole bank! Runs like total ****. 02?
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Old 11-04-2010, 10:14 PM   #11
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yeah it runs fine when its cold then goes into miss mode. Feels like a whole bank! Runs like total ****. 02?
Sounds like it to me.. You know anyone that has something you can check them with?
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Old 11-04-2010, 10:30 PM   #12
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I could bring it to a mechanic. Is there anyway I can check them? Can I switch the front ones to the back?
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Old 11-04-2010, 10:41 PM   #13
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I could bring it to a mechanic. Is there anyway I can check them? Can I switch the front ones to the back?
Front and rears are not interchangable. For what is costs a mechanic to diagnose it you could buy one. I would rather do that, I don't trust anyone with my car. You already have the misfire code. It may take some time to throw a code for the oxygen sensor, mine hasn't yet
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Old 11-05-2010, 08:53 AM   #14
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Oh okay...how bad is it to drive the car with misfires?
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Old 11-05-2010, 10:24 AM   #15
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Depends on how bad it is. Lockup with be disabled, and depending on your stall size will depend on how much extra heat is built in your tranny. Could foul plugs if its running rich on that bank...and being pig rich isn't the best thing for cats. You could remove the o2 sensors and see if they have any build up on them and clean them, worth a shot.
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Old 11-05-2010, 11:59 AM   #16
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Is it possible that the fuel filter is clogged? I ran my car on empty for a while a couple days ago. The fuel needle was way below E. I put a bottle of Techron Fuel System Cleaner in the tank hoping that would be my problem. Just now the car was running fine up and down the highway and all the power came back. When I went to start it again later the misfire came back and is constantly there. I think I may go with new 02s. Should I get 4 new ones?
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Old 11-05-2010, 02:21 PM   #17
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Is it possible that the fuel filter is clogged? I ran my car on empty for a while a couple days ago. The fuel needle was way below E. I put a bottle of Techron Fuel System Cleaner in the tank hoping that would be my problem. Just now the car was running fine up and down the highway and all the power came back. When I went to start it again later the misfire came back and is constantly there. I think I may go with new 02s. Should I get 4 new ones?
If you cant remember the last time you changed the filter I would change it. I would leave the rears alone until you get a code for them...I assume you have cats. You could buy one sensor and see if you get lucky the first try, then swap sides if the miss doesn't go away. I doubt both of them are bad.
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Old 11-05-2010, 02:42 PM   #18
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Quote:
Originally Posted by AgentLS1Z View Post
Is it the 02 sensors??? I've mostly been getting P0300. I got a Misfire on Cylinder #1 code, and a P0113 IAT sensor code. P0300 keeps coming up and its running like its only working on 3 or 4 cylinders. Its pretty bad. It's been raining constantly today and the misfire randomly started today. What do you guys think?

Car is 02 Z28
Does the car have headers? Water could be getting on the o2 sensor wires causing the misfire. When it rained, my last car would misfire occasionally. Turns out, my o2 sensor wire extensions connections were getting wet. If you don't have extensions it'd be worth checking the condition of the wires to make sure they're not getting water into the connections/wire itself.
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Old 11-07-2010, 03:30 PM   #19
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Does the car have headers? Water could be getting on the o2 sensor wires causing the misfire. When it rained, my last car would misfire occasionally. Turns out, my o2 sensor wire extensions connections were getting wet. If you don't have extensions it'd be worth checking the condition of the wires to make sure they're not getting water into the connections/wire itself.

No the car doesn't have headers.

I changed the fuel filter and the car was running good. But now the misfire is back. I'm not sure what the problem is but i'm leaning towards it being an 02 Sensor. I'll scan the codes again asap
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Old 11-07-2010, 03:51 PM   #20
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No the car doesn't have headers.

I changed the fuel filter and the car was running good. But now the misfire is back. I'm not sure what the problem is but i'm leaning towards it being an 02 Sensor. I'll scan the codes again asap
i have the same issue random missifres.

i changed the front o2s on both sides and still. changed fuel rails and fuel injectors and still also changed spark plugs and wires and still.

im beggining to think it may be ground related?
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1996, 96, code, coil, driving, egr, misfiers, misfire, misses, pack, rain, random, test, throws, z28

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