P0300 code, engine misfiring at hyway speeds
#42
06-05-2014, 08:37 PM
This will help with the adapter:
http://i561.photobucket.com/albums/s...ps5c876ad4.jpg
80MPH, (hmmm) 197F coolant temp, (perfect) perfect fuel trims, (something wrong here if it was misfiring) open loop, (something wrong here too, should be closed). Clear 'em out and do again
Is that the only data your scan tool shows in freeze frame?
http://i561.photobucket.com/albums/s...ps5c876ad4.jpg
80MPH, (hmmm) 197F coolant temp, (perfect) perfect fuel trims, (something wrong here if it was misfiring) open loop, (something wrong here too, should be closed). Clear 'em out and do again
Is that the only data your scan tool shows in freeze frame?
Ok, i got all the parts, but I have to get another hose barb. the one i found at pepboys is different then the one you listed and also doesnt fit my fuel gauge. so, i am stopping by my local Grainger to pick up the one you listed. Only thing though, the screw end of my fuel gauge is similar to a tire gauge, as it as a button that has to be depressed for the pressure to enter the gauge. So i am not sure if this adapter set up is goign to work, unless the hose barb depresses the button... So, i guess I will find out tomorrow and post the results
#43
06-05-2014, 09:50 PM
The "button" in your tester is what depresses the schrader valve in the service port on the engine. The fitting you're getting at Grainger does not have a schrader in it, so fuel will flow through the connection. Don't worry, it'll work
#44
06-10-2014, 07:25 PM
Fuel pressure is too low, possibly causing both DTC's to show up. Fuel pressure must be within spec so the correct amount of fuel is discharged when the injector opens. If pressure is too low, not enough fuel is discharged and the engine will run lean.
Fuel pressure, when tested at the service port, is regulated pressure. It is not what the pump is capable of building. The reading is the lowest pressure of the fuel pressure regulator setting, or the maximum output of the fuel pump, (whichever is lower). Without further testing, a guess would be a faulty fuel pressure regulator. To find out for certain what the problem is, more testing is necessary. The next step is to find out if the pump is able to supply sufficient pressure. This is done at the fuel filter outlet. The nylon outlet line is disconnected from the filter, and the pressure tester is modified so that it will connect directly to the filter. All fuel pressure and flow must end at the tester, with no fuel allowed to the fuel metering block on the engine, (leave the disconnected nylon line dangling). While the pump is activated, the stabilized pressure must be 73psi to 108psi, and it must remain above 55psi for at least 10 minutes after the pump shuts off. Post both readings.
Fuel pressure, when tested at the service port, is regulated pressure. It is not what the pump is capable of building. The reading is the lowest pressure of the fuel pressure regulator setting, or the maximum output of the fuel pump, (whichever is lower). Without further testing, a guess would be a faulty fuel pressure regulator. To find out for certain what the problem is, more testing is necessary. The next step is to find out if the pump is able to supply sufficient pressure. This is done at the fuel filter outlet. The nylon outlet line is disconnected from the filter, and the pressure tester is modified so that it will connect directly to the filter. All fuel pressure and flow must end at the tester, with no fuel allowed to the fuel metering block on the engine, (leave the disconnected nylon line dangling). While the pump is activated, the stabilized pressure must be 73psi to 108psi, and it must remain above 55psi for at least 10 minutes after the pump shuts off. Post both readings.
#45
06-10-2014, 07:45 PM
The white nylon clip on the fuel filter comes off, then the 800-121 snaps onto the filter. To remove it, pull the spring loaded black collar back toward the fitting, and slide the fitting off of the filter. No clip is necessary with the 800-121.
73psi is the minimum allowed, which means your pressure is OK, but it's borderline. Post the pressure after waiting 10 minutes and we'll see where it ends up.
73psi is the minimum allowed, which means your pressure is OK, but it's borderline. Post the pressure after waiting 10 minutes and we'll see where it ends up.
#46
06-11-2014, 08:58 PM
The white nylon clip on the fuel filter comes off, then the 800-121 snaps onto the filter. To remove it, pull the spring loaded black collar back toward the fitting, and slide the fitting off of the filter. No clip is necessary with the 800-121.
73psi is the minimum allowed, which means your pressure is OK, but it's borderline. Post the pressure after waiting 10 minutes and we'll see where it ends up.
73psi is the minimum allowed, which means your pressure is OK, but it's borderline. Post the pressure after waiting 10 minutes and we'll see where it ends up.
Ok, re-did the test. again the initial fuel pressure coming out of the fuel filter was at 75-76 psi. after 10-12 mins it dropped to 55-56 psi.
the engine light has come on again with the P0300 random misfire code.
all I/M Monitors were listed as ready
the freeze frame numbers are as follows:
abslt tps 45
rpm 2306
calc load 38.4
maf 65.66
map 91
coolant 199 deg
st ftrm1 2.3
lt ftrm1 -3.2
st ftrm2 5.4
lt ftrm2 2.3
speed 67 mph
fuel sys 1/2 closed
So, what is my next step?
#47
06-11-2014, 09:40 PM
Both the pressure and the leakdown are within specs, but they are both borderline. Any change for the worse, and she'll need a new fuel pump.
Fuel trims have been all over the place, with this last one, LTFT bank 1 is the only one that's screwy, and it's not all that bad. The others are a bit lean, while LTFT B1 is a tad rich. Bank 1 is cylinders 1, 3, and 5. If your scan tool showed live misfire data, it would tell exactly who's misfiring... no guess work involved.
Back in post #24, Camshaft retard and worn distributor bushings were mentioned, have you had them checked? If not, that's the next place to go... gotta make sure they're good.
Fuel trims have been all over the place, with this last one, LTFT bank 1 is the only one that's screwy, and it's not all that bad. The others are a bit lean, while LTFT B1 is a tad rich. Bank 1 is cylinders 1, 3, and 5. If your scan tool showed live misfire data, it would tell exactly who's misfiring... no guess work involved.
Back in post #24, Camshaft retard and worn distributor bushings were mentioned, have you had them checked? If not, that's the next place to go... gotta make sure they're good.
#48
07-01-2014, 09:47 AM
Both the pressure and the leakdown are within specs, but they are both borderline. Any change for the worse, and she'll need a new fuel pump.
Fuel trims have been all over the place, with this last one, LTFT bank 1 is the only one that's screwy, and it's not all that bad. The others are a bit lean, while LTFT B1 is a tad rich. Bank 1 is cylinders 1, 3, and 5. If your scan tool showed live misfire data, it would tell exactly who's misfiring... no guess work involved.
Back in post #24, Camshaft retard and worn distributor bushings were mentioned, have you had them checked? If not, that's the next place to go... gotta make sure they're good.
Fuel trims have been all over the place, with this last one, LTFT bank 1 is the only one that's screwy, and it's not all that bad. The others are a bit lean, while LTFT B1 is a tad rich. Bank 1 is cylinders 1, 3, and 5. If your scan tool showed live misfire data, it would tell exactly who's misfiring... no guess work involved.
Back in post #24, Camshaft retard and worn distributor bushings were mentioned, have you had them checked? If not, that's the next place to go... gotta make sure they're good.
As luck would have it, the truck was running fine that day, the engince light was off. they stated they couldn't find any codes and took it for a test drive and it ran fine. so, they didnt charge me for the check.
sure enough all that day and the next day, she ran like new, then the third day it started again with the misfiring at speeds around 65-70 mph. The engine lights comes on, then goes off. So, with the holiday weekend coming up, i can only bring it to the mecahnic on a friday or saturday because of work. I will wait to see if the engine light stays on and either take it back to STS or maybe another mechanic.
#49
11-02-2014, 09:38 PM
So that's it? I'm dying to hear the end of the mystery! Although my 'symptoms' are not identical, I've read all the posts on this thread (and others) to learn the solution to misfire problems with 4.3L engine. I for one, would appreciate knowing if you (serpico1) were able to resolve your misfire issue.
#50
11-04-2014, 08:13 AM
Well, It basically just stopped happening. Although, I did find that the boot connector for the vaccum line that runs to the PCV valve was cracked and although at normal idle it didnt seem to be leaking, if you jiggle the vaccum line, then you could hear the hissing and the engine would start running rough. So, I replaced it. dont know if that was the cause, but the engine has been running fine ever since. So, maybe at the higher speed, the vaccum line started to vibrate and the leak caused the misfiring. Thats all I can assume. Although, i find it strange that it was happening at almost the same speed and rpm everytime.