Random misfire, can't find problem
12-14-2016, 02:11 AM
#1
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Random misfire, can't find problem I have a 2000 trans am ls1. Headers, hot cam, and ls6 springs. No tune yet, but I drove it 5000 miles, without one, before it started doing this.While driving down the road I heard a loud pop that came from my exhaust. It literally sounds like a gun shot in my car. Then it didn't do anything for the rest of the drive home. The next day I was driving it to work and it did it again, But it kept doing it. If I hit the gas it quits misfiring and it seems to drive normal. But if I don't press the gas it keeps misfiring and it will then cut off. Rpm gauge will also quit working then it starts back randomly. Then I'll dump the clutch and it will start back. It was throwing a p0336 code so put a new CKPS in and it is still causing an issue. Maybe the wires? I checked them and they are fine. I thought maybe bad gas, so I put higher octane in it and still no change. I also put a new mass air flow on it and it is still doing the same. Also I took out the 02 sensors and cleaned them and still no change. It seems to do fine until it warms up.
P0336
P0412
P0102
P0443
P0300 (these are all the codes it is showing)
If anyone has any ideas please help! This is my daily and it is unbelievabley hard to drive like this. I have to keep it above 3700 just to keep it from misfiring.
P0336
P0412
P0102
P0443
P0300 (these are all the codes it is showing)
If anyone has any ideas please help! This is my daily and it is unbelievabley hard to drive like this. I have to keep it above 3700 just to keep it from misfiring.
12-14-2016, 12:27 PM
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Update I checked all the wires already but I will try again tonight. I also just replaced 1 02sensor it didn't change anything, I then swapped it to the other side and still no change.
12-14-2016, 04:33 PM
#6
Sounds like a crank sensor issue being that the tach acts up and it backfires. and the p0336 code is a crank sensor code. Try replacing the connector, it's called a pigtail.
I'd be most worried about p0102 and p0336. The other codes are emissions stuff and not a big deal. The p0300 will go away when you clear up the misfire issue.
I'd be most worried about p0102 and p0336. The other codes are emissions stuff and not a big deal. The p0300 will go away when you clear up the misfire issue.
12-16-2016, 10:37 PM
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Thanks for replying guys!
Okay, I checked the grounds (again) I even checked the back of the head. I unplugged that MAF for a bit. And neither of these things worked. I then also checked for voltage at the pigtail for the crank sensor. I was getting 11v from two wires. And the other is the ground. Is this right for that sensor? I also unplugged both 02 sensors (I don't have cats) it made no difference
Okay, I checked the grounds (again) I even checked the back of the head. I unplugged that MAF for a bit. And neither of these things worked. I then also checked for voltage at the pigtail for the crank sensor. I was getting 11v from two wires. And the other is the ground. Is this right for that sensor? I also unplugged both 02 sensors (I don't have cats) it made no difference
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12-17-2016, 03:57 AM
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Fixed! Kinda I went back into the garage, I pulled the whole harness going to the crank sensor. This included the signal off of the starter and the right side O2 sensor. I inspected all the wires and they were all good. Then I open the PCM were the wires are leading into and it was fine. I put it all back together and somehow it work. It's still misfires every now and then but it does not cut off while driving. also the check engine light went off( although it never came up again when it did misfire) I still need to track that down but I can definitely drive it back and forth to work now!
12-23-2016, 02:06 PM
#9
I went back into the garage, I pulled the whole harness going to the crank sensor. This included the signal off of the starter and the right side O2 sensor. I inspected all the wires and they were all good. Then I open the PCM were the wires are leading into and it was fine. I put it all back together and somehow it work. It's still misfires every now and then but it does not cut off while driving. also the check engine light went off( although it never came up again when it did misfire) I still need to track that down but I can definitely drive it back and forth to work now!
Sounds like a crank sensor issue being that the tach acts up and it backfires. and the p0336 code is a crank sensor code. Try replacing the connector, it's called a pigtail.
I'd be most worried about p0102 and p0336. The other codes are emissions stuff and not a big deal. The p0300 will go away when you clear up the misfire issue.
I'd be most worried about p0102 and p0336. The other codes are emissions stuff and not a big deal. The p0300 will go away when you clear up the misfire issue.
The pins in the pigtails get weak and don't make a good contact sometimes, one of the ways you'll know is by unplugging them and reconnecting. Try the pigtail, if you can't find one then you'll need to de pin the connecor and pry down on the tension tabs inside the connector with a tiny pick or a needle and see if that helps. Also the wires especially on gm cars i've found, will break right near the connector, the wiring itself inside the insulation, another reason it's good to try a pigtail. The way to tell if one is broken inside the insulation is to pull on it pretty good and see if it stretches, the wiring won't stretch but the insulation will, and the insulation will snap too right where the wire is broken. If that happens you'll need a pigtail or to repair that wire.
You can see why I really want you to try a pigtail lol.
Last edited by 00pooterSS; 12-23-2016 at 02:11 PM.
12-23-2016, 04:54 PM
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The pins in the pigtails get weak and don't make a good contact sometimes, one of the ways you'll know is by unplugging them and reconnecting. Try the pigtail, if you can't find one then you'll need to de pin the connecor and pry down on the tension tabs inside the connector with a tiny pick or a needle and see if that helps. Also the wires especially on gm cars i've found, will break right near the connector, the wiring itself inside the insulation, another reason it's good to try a pigtail. The way to tell if one is broken inside the insulation is to pull on it pretty good and see if it stretches, the wiring won't stretch but the insulation will, and the insulation will snap too right where the wire is broken. If that happens you'll need a pigtail or to repair that wire.
You can see why I really want you to try a pigtail lol.
You can see why I really want you to try a pigtail lol.
12-24-2016, 05:09 PM
#11
sorry I forgot to keep this updated. I did eventually try a new pigtail and it still was doing the same. I then took my car to a guy who tunes ls engines and he done a crank relearn. I've driven it 600 miles and no problem yet. I'm not sure why it would just go out when I was driving down the road. But so far so good!
Likely the connector or sensor failed and after you replaced it it needed the cam/crank correlation set. That's what he did it sounds like.
12-27-2016, 11:06 AM
#13
The only way I know is with a high end scanner, you go in and select the cam/crank correlation and the scanner commands the computer to enter a learning mode for the correlation between the two. I do it with a Snap on Solus Ultra. Smaller/lower cost scanners don't have that function.
12-27-2016, 02:06 PM
#14
The only way I know is with a high end scanner, you go in and select the cam/crank correlation and the scanner commands the computer to enter a learning mode for the correlation between the two. I do it with a Snap on Solus Ultra. Smaller/lower cost scanners don't have that function.
12-27-2016, 02:32 PM
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The other possibility is that the headers (maybe made
even worse by the duration of the hotcam) is making
fuel trim learning wander to a bad place and the "pop"
is the end of the bottoming-out. Clearing when you
high-idle it for a bit tends to point to sensor cooling
as a problem.
even worse by the duration of the hotcam) is making
fuel trim learning wander to a bad place and the "pop"
is the end of the bottoming-out. Clearing when you
high-idle it for a bit tends to point to sensor cooling
as a problem.
