Don Terrill’s Speed-Talk

If it has theintake "spider" then the fuel pressure is to low. The vortec uses much higher pressure. Don't overlook the filter either.

grant6395 wrote: ↑Thu May 03, 2018 10:13 am If it has theintake "spider" then the fuel pressure is to low. The vortec uses much higher pressure. Don't overlook the filter either.

No spider, it's an LS V8 Vortec, I believe normal running fuel pressure is 50 psi... Recent Wix filter and new fuel lines...I personally pulled the injectors and tried a set from my other truck that has no issues...But it didn't make any difference...
i have been told a "crank sensor relearn' might be the answer...

I have ran into the same issues with the misfire and fuel pressure. My money would be on it needs a fuel pump even though it is 45psi (seems like enough) is not enough.
Mitch

Truckedup wrote: ↑Thu May 03, 2018 9:08 am

gnicholson wrote: ↑Thu May 03, 2018 8:53 am The guy above is correct that it will set lean codes long before it will misfire from being to lean.

So what you are saying is PO300 is related to ignition issues or a mechanical problem more than actual fuel issues? I know how modern engine management works..but I'm from the thinking that if the engine pulls well under load and idles smooth, the ignition is doing it's job and the mechanical stuff must be ok.......

I would look at the long-term fuel trim table. There are all kinds of things that will set that code. Vacuum leaks dripping injectors ignition problems Etc.

S10LS2 wrote: ↑Wed May 02, 2018 10:44 pm

dirtracr5 wrote: ↑Wed May 02, 2018 10:25 pm No thats not low enough to cause a misfire. Use a scan tool capable of telling you which cylinder is misfiring as its happening then go from there.

Your way off man it is p0300 meaning multiple, not a p0302,304 etc etc. pressure is low enough for sure to cause"multiple" What do you think 45 psi drops to under load? It certainly does not go higher.

Gm vehicles almost always set a generic p0300. Use a scan tool to determine which cylinder or cylinders are causing the code. I am a GM tech. I work on these daily.

Truckedup wrote: ↑Thu May 03, 2018 9:08 am

gnicholson wrote: ↑Thu May 03, 2018 8:53 am The guy above is correct that it will set lean codes long before it will misfire from being to lean.

So what you are saying is PO300 is related to ignition issues or a mechanical problem more than actual fuel issues? I know how modern engine management works..but I'm from the thinking that if the engine pulls well under load and idles smooth, the ignition is doing it's job and the mechanical stuff must be ok.......

P0300 is a generic misfire code. You need a scan tool with a misfire counter or graph to see what cylinder is causing your issue. Then go from there with basic checks like spark, fuel and compression. Ive seen injectors, plugs, valve springs, cams, lifters, intake gasket leaks and piston/ring issues all cause misfires on these engines.

IF the motor doesn't have a noticable misfire then it probably has a buildup on the crank sensor wheel and is giving you a false misfire code, see this all the time as they get older, and whoever told you that it needs a crankshaft relearn is probably right. I work for a company with a fleet of 130 ls powered trucks in it, and i see it all the time. I would start there, especially if it shows in the misfire data random misfires on random cylinders with no rhyme or reason. If it was lean enough to actually misfire it would have lean codes in it also as already stated.

S10LS2 wrote: ↑Wed May 02, 2018 10:52 pm

peejay wrote: ↑Wed May 02, 2018 10:45 pm How old are the spark plugs?

Low fuel pressure will set lean codes LONG before it misfires. I've seen trucks running and driving at 9psi fuel pressure. (Okay, not running WELL, mind you...) If there are no lean codes present, and you don't have a scan tool to be able to watch live data while the problem happens, I'd first look at the spark plugs. 100k isn't a guideline, it's a "you mean you didn't have to replace them 40k ago? Wow, get those suckers out of there!" maximum.

Wow total bullshit, except for putting plugs and wires, its all a guessing game as the guy posts limited information. you can buy a scan tool for less then 100 bucks that will read live data.. Dont throw parts at it fix it. LOL 9 psi

As long as you have a smartphone, you can read live data for about $25. The app is free and the OBD2 adapter is around $25.

midnightbluS10 wrote: ↑Mon May 07, 2018 8:28 pm

S10LS2 wrote: ↑Wed May 02, 2018 10:52 pm

peejay wrote: ↑Wed May 02, 2018 10:45 pm How old are the spark plugs?

Low fuel pressure will set lean codes LONG before it misfires. I've seen trucks running and driving at 9psi fuel pressure. (Okay, not running WELL, mind you...) If there are no lean codes present, and you don't have a scan tool to be able to watch live data while the problem happens, I'd first look at the spark plugs. 100k isn't a guideline, it's a "you mean you didn't have to replace them 40k ago? Wow, get those suckers out of there!" maximum.

Wow total bullshit, except for putting plugs and wires, its all a guessing game as the guy posts limited information. you can buy a scan tool for less then 100 bucks that will read live data.. Dont throw parts at it fix it. LOL 9 psi

As long as you have a smartphone, you can read live data for about $25. The app is free and the OBD2 adapter is around $25.

I have an iphone and an ipad...So can you recommend the OBD2 wireless adapter and a particular App?....Do they display all the info such as fuel trims,timing, O2 sensors and various other information?

Truckedup wrote: ↑Tue May 08, 2018 7:00 am

midnightbluS10 wrote: ↑Mon May 07, 2018 8:28 pm

S10LS2 wrote: ↑Wed May 02, 2018 10:52 pm
Wow total bullshit, except for putting plugs and wires, its all a guessing game as the guy posts limited information. you can buy a scan tool for less then 100 bucks that will read live data.. Dont throw parts at it fix it. LOL 9 psi

As long as you have a smartphone, you can read live data for about $25. The app is free and the OBD2 adapter is around $25.

I have an iphone and an ipad...So can you recommend the OBD2 wireless adapter and a particular App?....Do they display all the info such as fuel trims,timing, O2 sensors and various other information?

https://www.obdsoftware.net/software/obdfusion

I use this mostly on Mopar platforms but it works with all makes. Originally got it on amazon several years ago and worked with the developer on some issues i was having with it regarding instant and average fuel economy results it was displaying.
Since then It's been flawless. Frequent updates and always improved features. Has a built in performance timer, HUD display capability, etc. I use a bluetooth adapter but the latest version also connects with a WiFi adapter. Installed it on my kindle fire HD6, website says it is compatible IOS 7 or later.

Not sure on cylinder misfire counts graphing but I would be surprised if it wasn't capable. May want to check with them before purchasing.

Thanks, I sent an email to them..

I would do a crank re-learn. If you approach that way any scan tool that can do that also can give you a misfire graph. Tech 2 is still the best but many after market scan tools can also do this(Autell, Snap-on, Matco, etc... and also Efi live and HP Tuners shops have this capability.

V Remian wrote: ↑Thu May 10, 2018 8:27 pm I would do a crank re-learn. If you approach that way any scan tool that can do that also can give you a misfire graph. Tech 2 is still the best but many after market scan tools can also do this(Autell, Snap-on, Matco, etc... and also Efi live and HP Tuners shops have this capability.

Least expensive tool that can do a relearn, from what I find, is the Autel MX808 , 360-400 bucks....There's rumors that the Foxwell NT510 can do it, about 200 bucks....
People say you can just drive into a local shop or dealership and ask for a relearn, supposedly less than $100....

BLstangin wrote: ↑Fri May 04, 2018 1:40 pm IF the motor doesn't have a noticable misfire then it probably has a buildup on the crank sensor wheel and is giving you a false misfire code, see this all the time as they get older, and whoever told you that it needs a crankshaft relearn is probably right. I work for a company with a fleet of 130 ls powered trucks in it, and i see it all the time. I would start there, especially if it shows in the misfire data random misfires on random cylinders with no rhyme or reason. If it was lean enough to actually misfire it would have lean codes in it also as already stated.

X2 for cam/crank relearn...anytime I see random misfire codes with none other ( p0300 only),,,I do the procedure...
A loose timing chain will set that code as well,,,Especially during cruise conditions.....

What do you techs prefer to use to clean the crank sensor with so it wont screw it up?