The dreaded P0300 code has come!! Help!
05-10-2016, 11:59 AM
#21
Le Mans Master
Leaking FPR will cause SES with misfire and rich codes. So I would change it then a drive car at high RPM to "clean" it out second gear works to keep from speeding tickets. after 5 or so minutes drive normally see how it does. P0300 may not self clear quickly
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chstitans42 (05-10-2016)
05-10-2016, 12:22 PM
#22
Good job I would check the oil for fuel and change it.
05-10-2016, 12:59 PM
#23
TheCorvetteBen
Thread Starter
So I changed it out, and the code came back after about a five min drive. I checked the fuel pressure and it is at a constant 30 psi, cold, hot and or with the rpms up.
I also took a timing light to each spark plug wire and watched to flash at idle and also at higher rpm. I did not see a miss or skips in the flash from the timing light.
I also took a timing light to each spark plug wire and watched to flash at idle and also at higher rpm. I did not see a miss or skips in the flash from the timing light.
05-10-2016, 01:18 PM
#24
So I changed it out, and the code came back after about a five min drive. I checked the fuel pressure and it is at a constant 30 psi, cold, hot and or with the rpms up.
I also took a timing light to each spark plug wire and watched to flash at idle and also at higher rpm. I did not see a miss or skips in the flash from the timing light.
I also took a timing light to each spark plug wire and watched to flash at idle and also at higher rpm. I did not see a miss or skips in the flash from the timing light.
have you done the filter?
05-10-2016, 01:20 PM
#25
TheCorvetteBen
Thread Starter
I cleared it, drove for 5 mins and it came back. Might try it a few more times. Usualy it takes less time to pop back up, like 30 seconds in. I haven't changed the filter but plan on it soon.
05-10-2016, 01:22 PM
#26
should go to 40 plus as soon as keyed on.
Last edited by antfarmer2; 05-10-2016 at 01:23 PM.
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chstitans42 (05-10-2016)
05-10-2016, 01:55 PM
#27
Instructor
Hey, Ben. I'm not C4 or Corvette expert but I have a lot of general auto experience and with modern EFI cars. VW/Audis are torture devices for DITY mechanics, for the record.
No way an O2 sensor will cause a misfire. The knock sensor overreacting is a very likely culprit. I'm not sure what disconnecting it will do to the 'Vette computer, but I'd try that if it won't throw a code or try a new one. One trick is to just remove it from the block and set it aside still plugged in. '90s knock sensors were just way too sensitive.
I'd check your fuel pressure spec at idle too. 30psi seems really low for an EFI based system. The last check would be the dreaded opti-spark and water pump leak. I sure hope it isn't that for your sake.
And for the record I'm starting to read the C4 forum, because I'm seriously considering adding a '93 40th anny RR to the '78 25th anny the wife and I purchased from you in a year or two. We will see how much cash santa brings this Christmas. And how much is left after I finish up the Miata engine swap.
A bad fuel pressure regulator will almost always cause a lean or rich code in one bank on a V8 too, especially in a return to tank EFI system. You aren't getting one of these too?
Last thought.... getting this code under load could be an indication of spark blowout caused by a weak spark. You could have plenty of juice at idle so you wouldn't see the problem on a strobe in the driveway. The normal culprits for this are usually bad wires, plugs or a weak old ignition module (and I sure hope it's not the module).
Oh and keep your eyes peeled for '93 40th anniversary 6 speed cars with less than 100k miles on the odo.
No way an O2 sensor will cause a misfire. The knock sensor overreacting is a very likely culprit. I'm not sure what disconnecting it will do to the 'Vette computer, but I'd try that if it won't throw a code or try a new one. One trick is to just remove it from the block and set it aside still plugged in. '90s knock sensors were just way too sensitive.
I'd check your fuel pressure spec at idle too. 30psi seems really low for an EFI based system. The last check would be the dreaded opti-spark and water pump leak. I sure hope it isn't that for your sake.
And for the record I'm starting to read the C4 forum, because I'm seriously considering adding a '93 40th anny RR to the '78 25th anny the wife and I purchased from you in a year or two. We will see how much cash santa brings this Christmas. And how much is left after I finish up the Miata engine swap.
A bad fuel pressure regulator will almost always cause a lean or rich code in one bank on a V8 too, especially in a return to tank EFI system. You aren't getting one of these too?
Last thought.... getting this code under load could be an indication of spark blowout caused by a weak spark. You could have plenty of juice at idle so you wouldn't see the problem on a strobe in the driveway. The normal culprits for this are usually bad wires, plugs or a weak old ignition module (and I sure hope it's not the module).
Oh and keep your eyes peeled for '93 40th anniversary 6 speed cars with less than 100k miles on the odo.
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chstitans42 (05-10-2016)
05-10-2016, 07:04 PM
#28
TheCorvetteBen
Thread Starter
05-10-2016, 07:16 PM
#29
TheCorvetteBen
Thread Starter
Hey, Ben. I'm not C4 or Corvette expert but I have a lot of general auto experience and with modern EFI cars. VW/Audis are torture devices for DITY mechanics, for the record.
No way an O2 sensor will cause a misfire. The knock sensor overreacting is a very likely culprit. I'm not sure what disconnecting it will do to the 'Vette computer, but I'd try that if it won't throw a code or try a new one. One trick is to just remove it from the block and set it aside still plugged in. '90s knock sensors were just way too sensitive.
I'd check your fuel pressure spec at idle too. 30psi seems really low for an EFI based system. The last check would be the dreaded opti-spark and water pump leak. I sure hope it isn't that for your sake.
And for the record I'm starting to read the C4 forum, because I'm seriously considering adding a '93 40th anny RR to the '78 25th anny the wife and I purchased from you in a year or two. We will see how much cash santa brings this Christmas. And how much is left after I finish up the Miata engine swap.
A bad fuel pressure regulator will almost always cause a lean or rich code in one bank on a V8 too, especially in a return to tank EFI system. You aren't getting one of these too?
Last thought.... getting this code under load could be an indication of spark blowout caused by a weak spark. You could have plenty of juice at idle so you wouldn't see the problem on a strobe in the driveway. The normal culprits for this are usually bad wires, plugs or a weak old ignition module (and I sure hope it's not the module).
Oh and keep your eyes peeled for '93 40th anniversary 6 speed cars with less than 100k miles on the odo.
No way an O2 sensor will cause a misfire. The knock sensor overreacting is a very likely culprit. I'm not sure what disconnecting it will do to the 'Vette computer, but I'd try that if it won't throw a code or try a new one. One trick is to just remove it from the block and set it aside still plugged in. '90s knock sensors were just way too sensitive.
I'd check your fuel pressure spec at idle too. 30psi seems really low for an EFI based system. The last check would be the dreaded opti-spark and water pump leak. I sure hope it isn't that for your sake.
And for the record I'm starting to read the C4 forum, because I'm seriously considering adding a '93 40th anny RR to the '78 25th anny the wife and I purchased from you in a year or two. We will see how much cash santa brings this Christmas. And how much is left after I finish up the Miata engine swap.
A bad fuel pressure regulator will almost always cause a lean or rich code in one bank on a V8 too, especially in a return to tank EFI system. You aren't getting one of these too?
Last thought.... getting this code under load could be an indication of spark blowout caused by a weak spark. You could have plenty of juice at idle so you wouldn't see the problem on a strobe in the driveway. The normal culprits for this are usually bad wires, plugs or a weak old ignition module (and I sure hope it's not the module).
Oh and keep your eyes peeled for '93 40th anniversary 6 speed cars with less than 100k miles on the odo.
05-10-2016, 07:18 PM
#30
TheCorvetteBen
Thread Starter
http://vid170.photobucket.com/albums...pszx5gx6fe.mp4
^^^^VIDEO
Click on the image above and it will take you to a video of the fuel pressure when the engine is running. you can see the fuel pressure while the engine is hot, at idle, and then revved a little. When I was clearing out the hose I noticed that the gas was a yellow color. Kinda odd,
^^^^VIDEO
Click on the image above and it will take you to a video of the fuel pressure when the engine is running. you can see the fuel pressure while the engine is hot, at idle, and then revved a little. When I was clearing out the hose I noticed that the gas was a yellow color. Kinda odd,
Last edited by chstitans42; 05-11-2016 at 09:36 AM.
05-10-2016, 09:01 PM
#32
05-10-2016, 10:06 PM
#33
Melting Slicks
The knock sensor overreacting is a very likely culprit. I'm not sure what disconnecting it will do to the 'Vette computer, but I'd try that if it won't throw a code or try a new one. One trick is to just remove it from the block and set it aside still plugged in. '90s knock sensors were just way too sensitive.
This matches my theory,
05-10-2016, 11:10 PM
#34
Melting Slicks
What about this;
"How the car runs: I have had this car for 2 weeks, and during the test drive and also during the 200 miles I have driven the car, it has ran just flawlessly. this recently came up about a week ago. The strange part is at idle, it runs smooth as a top. Once you get between 1500-2500 rpm you can hear and feel the miss, engine runs rough, not much power at all. Also today while doing a test drive I heard a little popping coming out of the tail pipe. Basically I have a miss under load."
OP has something amiss! no pun..
"How the car runs: I have had this car for 2 weeks, and during the test drive and also during the 200 miles I have driven the car, it has ran just flawlessly. this recently came up about a week ago. The strange part is at idle, it runs smooth as a top. Once you get between 1500-2500 rpm you can hear and feel the miss, engine runs rough, not much power at all. Also today while doing a test drive I heard a little popping coming out of the tail pipe. Basically I have a miss under load."
OP has something amiss! no pun..
05-10-2016, 11:52 PM
#35
TheCorvetteBen
Thread Starter
05-11-2016, 06:22 AM
#36
05-11-2016, 03:41 PM
#38
Instructor
I did some poking around and found out the fuel pressure spec is 43 psi from the factory. Since you are at 30, you will drop pressure under load and you are having a lean knock. Lean is dangerous. I wouldn't drive your 'Vette until you get this solved.
You should start with the easy stuff, the fuel filter, and then you will have to go in the tank and check the pickup, pickup sock, and fuel pump itself. You will also want to make sure the tank is clean. My guess is being an older car you have some tank corrosion that's causing this problem. It's a real pain to fix this problem. If you have rust in your tank, it'll be easier to replace it than try to fix it.
https://www.corvetteforum.com/forums...-big-pics.html
You should start with the easy stuff, the fuel filter, and then you will have to go in the tank and check the pickup, pickup sock, and fuel pump itself. You will also want to make sure the tank is clean. My guess is being an older car you have some tank corrosion that's causing this problem. It's a real pain to fix this problem. If you have rust in your tank, it'll be easier to replace it than try to fix it.
https://www.corvetteforum.com/forums...-big-pics.html
05-11-2016, 04:50 PM
#39
Much easyer to clean the tank than replacing it.
05-11-2016, 08:21 PM
#40
TheCorvetteBen
Thread Starter
I figured it was a fuel issue seeing it just came after running so great for a while. Next step is the fuel filter, and then check psi. then pickup sock, check psi and then pump itself, then check psi
