HELP: 99 Camaro wont Start, Misfire, & P0300 code
HELP: 99 Camaro wont Start, Misfire, & P0300 code I have seen a lot of threads in regards to the infamous P0300 Code, and a bad misfire. I am currently in the process of trying to figure out what is wrong with my car.
The car is a 99 Z28. I have Headers, FTRA, Summit TB, Lid, K&N Filter, and 160,xxx miles.
Notes for story under long paragraph.
A little background about how it started. It started running rough, and black soot was coming out of the car because it was so rich. Had SRJ, and a couple of guys look at it and they found I had two Vacuum leaks. Both vacuum leaks were fixed and at the same time I had the injectors changed, thinking maybe I had a leaky injector. At first I thought maybe my issue was a fuel pump. After the vacuum leaks, and injectors car seemed strong again. Fast forward a couple of days, I pick up an LS6 intake from my buddy Tuesday night. Tuesday night/ Wednesday I work to install the intake (OSU i did break) Everything was failry straight forward on the install.
After I installed it i forgot to put the brake booster on, and it was running bad. I noticed it, and re-connected. Wednesday it was raining so I wasnt able to test the cars difference but there was not idle issues or misfires. The car ran great Wednesday until later that night it had a slight 15 sec stumble like it was fuel starved, then it was fine. All day thursday the car was perfect. Friday at 12 somthing on New Years the car stars the stumbling and dies coming off the freeway. Take me 5 time of starting, and throwing the car in Nuetral to get home.
To make a long story short, I put the LS1 intake back on thinking I screwed up the LS6 intake install. The car continued to not turn over. It was if i didint have fuel. I changed the Fuel filter, checked the fuel pressure which was about 48psi. Still nothing changed.. I looked over the car noticed Engine Sensor Fuse Blown, Changed it. The car would start and I could drive it, but it had a misfire. Ran the scanner came up with P0300 Code.
I then changed all the spark plugs, wires, (old plugs were black, carbon covered, only had these in about 5 months or less) O2 Sensors, put the ls6 intake back on, and double checked everything. Car now starts but shakes bad. This is where I am currently. Code still showed up after this.
Notes of this long story.
-Installed LS6 Intake was fine for Two days
-Car died, and I limped home
-Un-installed LS6 intake, put on LS1, still wouldnt start without me gasing it
-Changed Engine Sensor Fuse, Car then started but was misfiring P0300 code
-Changed spark plugs, old ones of 5 months were carbon covered, and smelled like fuel.
-Changed wires, LS6 intake re-installed, car still wouldnt start
-Changed 02 sensors, no real change
-Car vibrates really bad, gets worse in reverse, wont stay on, and eventually dies.
I am goining to continue on the trail to figure it out, and will keep this thread updated because it seems like a lot of people get this P0300 code, or the car acts funny. Any insight or suggestions is appreciated. I am going to have a real diagnostic done, and probaly a compression test. Thanks for reading, and any help given.
The car is a 99 Z28. I have Headers, FTRA, Summit TB, Lid, K&N Filter, and 160,xxx miles.
Notes for story under long paragraph.
A little background about how it started. It started running rough, and black soot was coming out of the car because it was so rich. Had SRJ, and a couple of guys look at it and they found I had two Vacuum leaks. Both vacuum leaks were fixed and at the same time I had the injectors changed, thinking maybe I had a leaky injector. At first I thought maybe my issue was a fuel pump. After the vacuum leaks, and injectors car seemed strong again. Fast forward a couple of days, I pick up an LS6 intake from my buddy Tuesday night. Tuesday night/ Wednesday I work to install the intake (OSU i did break) Everything was failry straight forward on the install.
After I installed it i forgot to put the brake booster on, and it was running bad. I noticed it, and re-connected. Wednesday it was raining so I wasnt able to test the cars difference but there was not idle issues or misfires. The car ran great Wednesday until later that night it had a slight 15 sec stumble like it was fuel starved, then it was fine. All day thursday the car was perfect. Friday at 12 somthing on New Years the car stars the stumbling and dies coming off the freeway. Take me 5 time of starting, and throwing the car in Nuetral to get home.
To make a long story short, I put the LS1 intake back on thinking I screwed up the LS6 intake install. The car continued to not turn over. It was if i didint have fuel. I changed the Fuel filter, checked the fuel pressure which was about 48psi. Still nothing changed.. I looked over the car noticed Engine Sensor Fuse Blown, Changed it. The car would start and I could drive it, but it had a misfire. Ran the scanner came up with P0300 Code.
I then changed all the spark plugs, wires, (old plugs were black, carbon covered, only had these in about 5 months or less) O2 Sensors, put the ls6 intake back on, and double checked everything. Car now starts but shakes bad. This is where I am currently. Code still showed up after this.
Notes of this long story.
-Installed LS6 Intake was fine for Two days
-Car died, and I limped home
-Un-installed LS6 intake, put on LS1, still wouldnt start without me gasing it
-Changed Engine Sensor Fuse, Car then started but was misfiring P0300 code
-Changed spark plugs, old ones of 5 months were carbon covered, and smelled like fuel.
-Changed wires, LS6 intake re-installed, car still wouldnt start
-Changed 02 sensors, no real change
-Car vibrates really bad, gets worse in reverse, wont stay on, and eventually dies.
I am goining to continue on the trail to figure it out, and will keep this thread updated because it seems like a lot of people get this P0300 code, or the car acts funny. Any insight or suggestions is appreciated. I am going to have a real diagnostic done, and probaly a compression test. Thanks for reading, and any help given.
Last edited by EVERETTDREW; Jan 11, 2011 at 05:59 PM.
This is how my car sounds, this is somones elses video of there car. I will post a video of mine.
I fought a Misfire in my 99 GMC Sonoma a few years ago. I can't say it ran as rough as your T/A in the video, but here is my story...
Along with a PO300, I was getting a PO339, Crankshaft Position Sensor Intermittent Signal.
When I had first purchased the truck, I had replaced both the Cam and Crank Sensors with new ones from Autozone, in an attempt to revive some of the spunk I thought this 4.3L V6 was lacking.
So with this PO339 Code I figured the Crank Sensor had failed. I returned it to the Zone under warranty and replaced it with a new one. No luck. The misfire remained.
I did all the easy ****, like plugs, wires, cap, and rotor, still nothing.
Then I moved on to the more expensive parts. I replaced all my O2 Sensors, coil, MAF Sensor, even the PCM. I went to the extreme of tearing the intake off to replace the Intake Gaskets, thinking maybe I had a small vacuum leak. I was getting desperate. Nothing! I was still getting the misfire and the two codes.
I also recall, unplugging my CKPS and trying to start the truck, to see if it would run any better in Open Loop. No. It won't start at all without a signal from the CKPS.
So as a last-ditch effort I thought I'd try a new GM Crank Position Sensor. I went to the local dealership and Tom there gave me the best deal he could on a CKPS for my Sonoma. It still cost me $90.
Lo-and-behold the Sensor from GM did the trick. I'm not sure of the Magnet in the one from Autozone was just not strong enough to consistantly pickup the signal from the reluctor wheel or what the deal was, but the new Delco Sensor worked. No more misfire.
Not sure if this helps, but I thought I'd throw it out there.
The way your car has trouble starting reminds me of trying to start my pickup with the CKPS unplugged. It'd just turnover and turnover but never fire. Maybe that's a direction you can look into?
Be sure to post up when you figure it out. I'd love to know what fixed the problem for future reference. Good luck, man!
Along with a PO300, I was getting a PO339, Crankshaft Position Sensor Intermittent Signal.
When I had first purchased the truck, I had replaced both the Cam and Crank Sensors with new ones from Autozone, in an attempt to revive some of the spunk I thought this 4.3L V6 was lacking.
So with this PO339 Code I figured the Crank Sensor had failed. I returned it to the Zone under warranty and replaced it with a new one. No luck. The misfire remained.
I did all the easy ****, like plugs, wires, cap, and rotor, still nothing.
Then I moved on to the more expensive parts. I replaced all my O2 Sensors, coil, MAF Sensor, even the PCM. I went to the extreme of tearing the intake off to replace the Intake Gaskets, thinking maybe I had a small vacuum leak. I was getting desperate. Nothing! I was still getting the misfire and the two codes.
I also recall, unplugging my CKPS and trying to start the truck, to see if it would run any better in Open Loop. No. It won't start at all without a signal from the CKPS.
So as a last-ditch effort I thought I'd try a new GM Crank Position Sensor. I went to the local dealership and Tom there gave me the best deal he could on a CKPS for my Sonoma. It still cost me $90.
Lo-and-behold the Sensor from GM did the trick. I'm not sure of the Magnet in the one from Autozone was just not strong enough to consistantly pickup the signal from the reluctor wheel or what the deal was, but the new Delco Sensor worked. No more misfire.
Not sure if this helps, but I thought I'd throw it out there.
The way your car has trouble starting reminds me of trying to start my pickup with the CKPS unplugged. It'd just turnover and turnover but never fire. Maybe that's a direction you can look into?
Be sure to post up when you figure it out. I'd love to know what fixed the problem for future reference. Good luck, man!
I fought a Misfire in my 99 GMC Sonoma a few years ago. I can't say it ran as rough as your T/A in the video, but here is my story...
Along with a PO300, I was getting a PO339, Crankshaft Position Sensor Intermittent Signal.
When I had first purchased the truck, I had replaced both the Cam and Crank Sensors with new ones from Autozone, in an attempt to revive some of the spunk I thought this 4.3L V6 was lacking.
So with this PO339 Code I figured the Crank Sensor had failed. I returned it to the Zone under warranty and replaced it with a new one. No luck. The misfire remained.
I did all the easy ****, like plugs, wires, cap, and rotor, still nothing.
Then I moved on to the more expensive parts. I replaced all my O2 Sensors, coil, MAF Sensor, even the PCM. I went to the extreme of tearing the intake off to replace the Intake Gaskets, thinking maybe I had a small vacuum leak. I was getting desperate. Nothing! I was still getting the misfire and the two codes.
I also recall, unplugging my CKPS and trying to start the truck, to see if it would run any better in Open Loop. No. It won't start at all without a signal from the CKPS.
So as a last-ditch effort I thought I'd try a new GM Crank Position Sensor. I went to the local dealership and Tom there gave me the best deal he could on a CKPS for my Sonoma. It still cost me $90.
Lo-and-behold the Sensor from GM did the trick. I'm not sure of the Magnet in the one from Autozone was just not strong enough to consistantly pickup the signal from the reluctor wheel or what the deal was, but the new Delco Sensor worked. No more misfire.
Not sure if this helps, but I thought I'd throw it out there.
The way your car has trouble starting reminds me of trying to start my pickup with the CKPS unplugged. It'd just turnover and turnover but never fire. Maybe that's a direction you can look into?
Be sure to post up when you figure it out. I'd love to know what fixed the problem for future reference. Good luck, man!
Along with a PO300, I was getting a PO339, Crankshaft Position Sensor Intermittent Signal.
When I had first purchased the truck, I had replaced both the Cam and Crank Sensors with new ones from Autozone, in an attempt to revive some of the spunk I thought this 4.3L V6 was lacking.
So with this PO339 Code I figured the Crank Sensor had failed. I returned it to the Zone under warranty and replaced it with a new one. No luck. The misfire remained.
I did all the easy ****, like plugs, wires, cap, and rotor, still nothing.
Then I moved on to the more expensive parts. I replaced all my O2 Sensors, coil, MAF Sensor, even the PCM. I went to the extreme of tearing the intake off to replace the Intake Gaskets, thinking maybe I had a small vacuum leak. I was getting desperate. Nothing! I was still getting the misfire and the two codes.
I also recall, unplugging my CKPS and trying to start the truck, to see if it would run any better in Open Loop. No. It won't start at all without a signal from the CKPS.
So as a last-ditch effort I thought I'd try a new GM Crank Position Sensor. I went to the local dealership and Tom there gave me the best deal he could on a CKPS for my Sonoma. It still cost me $90.
Lo-and-behold the Sensor from GM did the trick. I'm not sure of the Magnet in the one from Autozone was just not strong enough to consistantly pickup the signal from the reluctor wheel or what the deal was, but the new Delco Sensor worked. No more misfire.
Not sure if this helps, but I thought I'd throw it out there.
The way your car has trouble starting reminds me of trying to start my pickup with the CKPS unplugged. It'd just turnover and turnover but never fire. Maybe that's a direction you can look into?
Be sure to post up when you figure it out. I'd love to know what fixed the problem for future reference. Good luck, man!
I thought the 48 PSI seemed low also. But someone told me it was ok. I will re-check the pressure now that the car can stay on. And I will see what the pressure reads over a period of time. Thanks for this input.
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Verdad Gallardo Started taking the plugs that I just installed on Saturday out and there already getting fouled. Smell like gas and have carbon on the end. They were dry. I am going to try some different coilpacks this weekend.
This is good to know. Once o get the plugs back in I will verify psi. Maybe this is a dumb question will a dying pump cause the car to run rich? I'm going to add a newer pcv pipe hoping that maybe it will fix something since mine was brittle. Also going to try a buddies coil packs.
The pcm is trying to over compensate (dumping more fuel) because it's not getting the proper psi.. Try the coil swap if you want, but these coils hardly ever go bad.. GM fuel pumps are another story.. Start with the obvious, once you varify the low psi at the rail again.
I will check the fuel pressure today, idling and under load.
When I took the MAP sensor off this last time one of the orange rings at the bottom was coming off, maybe that is an issue.
These are the stock injector sizes below:
1998: 28.6 lb/hr
1999-2000: 26.4 lb/hr
2001-2002: 28.8 lb/hr
The true size of the injector for my car is 22, and for 98,01,02 is 24. Will this make a big differcne and make my car run more rich since it is in my computer to run for 22? Or am I reaching to far on this?
When I took the MAP sensor off this last time one of the orange rings at the bottom was coming off, maybe that is an issue.
These are the stock injector sizes below:
1998: 28.6 lb/hr
1999-2000: 26.4 lb/hr
2001-2002: 28.8 lb/hr
The true size of the injector for my car is 22, and for 98,01,02 is 24. Will this make a big differcne and make my car run more rich since it is in my computer to run for 22? Or am I reaching to far on this?
Well if you get the P0300 misfire code then you might get nervous. Turns out I have a badly bent intake valve, and a bent pushrod on number cylinder #7. Had Chris and Jason check it out in OC. Looks like its time to start getting the parts together. Just wanted to updat this thread since I know other people have this issue. What casued this to happen, im not sure.
Dredging up an old thread. I am having a similar misfire issue with P0300. Fuel pressure is at 52 psi measured on the schrader valve on my fuel rail. Is that too low?
