Bad Misfire
12-11-2012, 01:09 PM
#1
Staging Lane
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Bad Misfire Hey guys, I've been having some issues with my car (2000 Trans Am WS6). Randomly driving home the other night I went to accelerate from a stop sign and the car started shaking and seemed like it lost like half its power. I knew it was a misfire but the surprising thing is when I pressed the gas a little more it just *sprung* out of it like nothing ever happened. Then it started doing it again and this time the SES light came on and started flashing. Long story short I've been trying not to drive my car much but if I have to (its my dd) it seems like it only has the problem when its cold or just starts to warm up. Once its hot the misfire goes away and all is well. I'm kinda stumped here (no I haven't got it scanned yet, plan on doing that Thursday) but do you guys have any ideas? I searched on here but couldn't find anything that related to my exact problem.
Btw its got new ACDelco iridium plugs and new MSD wires. The car also has headers but I checked the wires and they aren't burnt from what I could see and they are all tight.
Here's a quick vid.
http://www.youtube.com/watch?v=Xp0re...ature=youtu.be
Btw its got new ACDelco iridium plugs and new MSD wires. The car also has headers but I checked the wires and they aren't burnt from what I could see and they are all tight.
Here's a quick vid.
http://www.youtube.com/watch?v=Xp0re...ature=youtu.be
12-11-2012, 09:47 PM
#3
Staging Lane
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Umm.. not sure actually, since I've owned the car (about 7 months I've never replaced them). Thinking about it that might be the problem, when the car is dead cold it doesn't misfire, when it starts to misfire it warms up and when its fully warm it quits misfiring again. O2s don't work until the car is warmed up right? Thanks for the reply
12-11-2012, 10:17 PM
#5
Staging Lane
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Well after doing some more research, I don't think a bad o2 will cause a misfire so yea its probably a coil. My scanner will be in tomorrow so I'll let you guys know what I find.
12-12-2012, 05:46 PM
#6
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Ok, after hooking my scan tool up to the car I got two codes, P0300 and P0152. So I cleared the codes then started the car and waited for it to start misfiring again and when the SES light came on I shut the car off and read to see what code it was and it was a P0306... So I know its #6 cylinder that's causing the misfire. As far as the P0152, which is '02 Sensor Circuit High Voltage (Bank 2 Sensor 1)' Would a misfire on #6 cause that to misread or fail entirely?
12-12-2012, 10:22 PM
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Ok, after hooking my scan tool up to the car I got two codes, P0300 and P0152. So I cleared the codes then started the car and waited for it to start misfiring again and when the SES light came on I shut the car off and read to see what code it was and it was a P0306... So I know its #6 cylinder that's causing the misfire. As far as the P0152, which is '02 Sensor Circuit High Voltage (Bank 2 Sensor 1)' Would a misfire on #6 cause that to misread or fail entirely?
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12-12-2012, 11:40 PM
#8
Ok, after hooking my scan tool up to the car I got two codes, P0300 and P0152. So I cleared the codes then started the car and waited for it to start misfiring again and when the SES light came on I shut the car off and read to see what code it was and it was a P0306... So I know its #6 cylinder that's causing the misfire. As far as the P0152, which is '02 Sensor Circuit High Voltage (Bank 2 Sensor 1)' Would a misfire on #6 cause that to misread or fail entirely?
When they start to fail....YES...they do cause misfires. They cause a rich condition which causes misfires, hesitation, stumbling and loss of power, then when you press the gas pedal and open the TB blade you lean it out and it takes off strong.
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12-14-2012, 01:05 AM
#9
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So I pulled all 8 spark plugs out and re gapped them to .040, put them back in and tested the coil packs with a multi meter. I put one of the prongs on first pin and the other prong on the other three to check resistance. Pins 2 and 3 on the good coils read around 120 ohms and the 4th pin read about 70 ohms. When I checked #6 pins 2 and 3 were at about 36 ohms and the 4th one was like 15... So I'm picking up a new coil tomorrow in the morning and I'll update you guys to see if it cures my problem. If not, I'll get a new O2 sensor.
12-14-2012, 01:49 AM
#10
So I pulled all 8 spark plugs out and re gapped them to .040, put them back in and tested the coil packs with a multi meter. I put one of the prongs on first pin and the other prong on the other three to check resistance. Pins 2 and 3 on the good coils read around 120 ohms and the 4th pin read about 70 ohms. When I checked #6 pins 2 and 3 were at about 36 ohms and the 4th one was like 15... So I'm picking up a new coil tomorrow in the morning and I'll update you guys to see if it cures my problem. If not, I'll get a new O2 sensor.
.040 is more of a nitrous gap. Its not terrible, but its definitely not optimal for N/A engines.
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12-14-2012, 12:52 PM
#11
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Well the coil didn't fix the problem... So I guess I need to pick up an O2 sensor, just ACDelco?
And yea about the spark plug gap... do you think it'll be fine with the .040 gap? or do I need to purchase a nitrous kit lol jk.
Autozone carries Denso, I'll just get one of those.
And yea about the spark plug gap... do you think it'll be fine with the .040 gap? or do I need to purchase a nitrous kit lol jk.
Autozone carries Denso, I'll just get one of those.
Last edited by av8er1555; 12-14-2012 at 01:06 PM.
12-14-2012, 09:29 PM
#12
Well the coil didn't fix the problem... So I guess I need to pick up an O2 sensor, just ACDelco?
And yea about the spark plug gap... do you think it'll be fine with the .040 gap? or do I need to purchase a nitrous kit lol jk.
Autozone carries Denso, I'll just get one of those.
And yea about the spark plug gap... do you think it'll be fine with the .040 gap? or do I need to purchase a nitrous kit lol jk.
Autozone carries Denso, I'll just get one of those.
Hahaha....yea, a 250 DP shot will do it.
Go to rockauto.com or amazon.com
Get the Denso 02 sensors...they're the best. They sell for $35-$45 each at those sites. Densos are EXACTLY what you will get in the AC Delco box at any GM dealership. They use Denso 02 sensors as their own.
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12-15-2012, 01:02 PM
#13
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Update: Got the O2 sensor in and all is well 
I had no idea that a failing O2 could cause a car to run that bad lol. So thanks everyone for the help!
I had no idea that a failing O2 could cause a car to run that bad lol. So thanks everyone for the help!
01-01-2013, 04:22 PM
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was the miss just in #6? I have been fighting with my 5.3 (2004 avalanche) for a couple weeks now. miss fire in #6. i can watch it real time on my Diablo tuner. Ive swapped plugs, wires, coils, injectors, compression is around 170, got good pulses on the injectors, and good spark. I just did a intake manifold gasket today and the miss hasn't moved or changed. Im at a loss.
