Random misfire #4
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From: Utah
Random misfire #4 Trying to help a buddy diagnose his 00 T/A before he deploys to Iraq. The car does not like to start, but when it does sounds like its missing pretty bad (sounds like a huge cam). The car is bone stock...not even a K&N filter. So far a new coil pack, plugs, wires and front 02's have been added. All I can think of is either an injector is stuck open, or maybe mechanical issues....bent push rod or broken valve spring. Damn, maybe the crank sensor is going? I don't know what else to do here. Please chime in.
Thanks.
Thanks.
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From: So.Cal.
How did you determine it is #4...?
If injector is stuck open, you would see rail pressure drop during key on engine off; confirm by removing spark plug is it wet, can you smell gas.
If the injector is not stuck open, then: is spark plug firing (test for visible arc), is injector firing (test for visible spray pattern).
Perform compression test and compare cylinders.
Perform cooling system pressure test.
If injector is stuck open, you would see rail pressure drop during key on engine off; confirm by removing spark plug is it wet, can you smell gas.
If the injector is not stuck open, then: is spark plug firing (test for visible arc), is injector firing (test for visible spray pattern).
Perform compression test and compare cylinders.
Perform cooling system pressure test.
is it a stick? if so the push rod is possible. but the one's ive seen bent doesnt cause a miss. get some tools to test the inj. maybe its clogged or stuck open.
blown headgasket..........
do a compression test. that will narrow it down some
blown headgasket..........
do a compression test. that will narrow it down some
You replaced all those parts and it didn't fix anything??? What an idiot. (touche')
No need to be a jerk dude just because someone didn't give you the magic answer when you provided hardly any diagnostic information to help you with, but you are right, it could be an injector, valve spring, or bent push rod.. did you happen to check any of those things yet?
Also try these things below.
do a fuel pressure drop test to try to confirm the injector leak/being stuck
stethescope the injector to see if it is functioning
check the injector circuit for pwr/ground/signal from the PCM
check compression
report results and we can give you some actual answers.
Last edited by 00pooterSS; Jun 29, 2011 at 03:58 PM.
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From: Utah
You replaced all those parts and it didn't fix anything??? What an idiot. (touche')
No need to be a jerk dude just because someone didn't give you the magic answer when you provided hardly any diagnostic information to help you with, but you are right, it could be an injector, valve spring, or bent push rod.. did you happen to check any of those things yet?
Also try these things below.
do a fuel pressure drop test to try to confirm the injector leak/being stuck
stethescope the injector to see if it is functioning
check the injector circuit for pwr/ground/signal from the PCM
check compression
report results and we can give you some actual answers.
No need to be a jerk dude just because someone didn't give you the magic answer when you provided hardly any diagnostic information to help you with, but you are right, it could be an injector, valve spring, or bent push rod.. did you happen to check any of those things yet?
Also try these things below.
do a fuel pressure drop test to try to confirm the injector leak/being stuck
stethescope the injector to see if it is functioning
check the injector circuit for pwr/ground/signal from the PCM
check compression
report results and we can give you some actual answers.
Guess Im an idiot posting, seeing if anyone else has had this same issue...ya my bad
I think the person who assumes there's a magical answer is an idiot. No such thing with troubleshooting, but I guess that's the name of the game. But hell, I guess I got the needed attention I was looking for, so sometimes you have to be a dick. I know...
Either way, next were swapping his injector(s) and valve-train if that doesn't work. The PCM keeps throwing the 300 series code...Misfire #4. Well my buddy is giving back to our country, its the least I could do to help him out....
Guess Im an idiot posting, seeing if anyone else has had this same issue...ya my bad I think the person who assumes there's a magical answer is an idiot. No such thing with troubleshooting, but I guess that's the name of the game. But hell, I guess I got the needed attention I was looking for, so sometimes you have to be a dick. I know... Either way, next were swapping his injector(s) and valve-train if that doesn't work. The PCM keeps throwing the 300 series code...Misfire #4. Well my buddy is giving back to our country, its the least I could do to help him out....
I think the person who assumes there's a magical answer is an idiot. No such thing with troubleshooting, but I guess that's the name of the game. But hell, I guess I got the needed attention I was looking for, so sometimes you have to be a dick. I know... Either way, next were swapping his injector(s) and valve-train if that doesn't work. The PCM keeps throwing the 300 series code...Misfire #4. Well my buddy is giving back to our country, its the least I could do to help him out....Did you ever do a compression test on that cylinder? Have you tried a fuel pressure drop to see if pressure falls really quickly?
And no... you didn't get the attention because you were a dick, you got it because the first 25 people that viewed that you were complaining about, decided not to post because your info is pretty vague and their answers would be guesses, the others threw out vague guesses as did I. Did it help? Doesn't appear to have because you still haven't tested any of the things you guessed it might possibly be. So instead of crying on the internet go do something and come back with info we can use.
And we all want to support our troops, but name dropping your buddy for being in the service and trying to help him all while acting like a douce, does not make you look like any less of a douce.
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Thread Starter
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From: Utah
As for testing components, make sure you just swap one thing at a time so that you know which exact component caused the misfire, I would swap the injector only! then retest, then try the spark plug only, and so on. You would be surprised how many bad spark plugs I have seen out of the box, I have not seen it from NGK, but on several other brands and quite a few AC Delco's. If you swap multiple things at once then you don't know which one was the culprit.
Did you ever do a compression test on that cylinder? Have you tried a fuel pressure drop to see if pressure falls really quickly?
And no... you didn't get the attention because you were a dick, you got it because the first 25 people that viewed that you were complaining about, decided not to post because your info is pretty vague and their answers would be guesses, the others threw out vague guesses as did I. Did it help? Doesn't appear to have because you still haven't tested any of the things you guessed it might possibly be. So instead of crying on the internet go do something and come back with info we can use.
And we all want to support our troops, but name dropping your buddy for being in the service and trying to help him all while acting like a douce, does not make you look like any less of a douce.
Did you ever do a compression test on that cylinder? Have you tried a fuel pressure drop to see if pressure falls really quickly?
And no... you didn't get the attention because you were a dick, you got it because the first 25 people that viewed that you were complaining about, decided not to post because your info is pretty vague and their answers would be guesses, the others threw out vague guesses as did I. Did it help? Doesn't appear to have because you still haven't tested any of the things you guessed it might possibly be. So instead of crying on the internet go do something and come back with info we can use.
And we all want to support our troops, but name dropping your buddy for being in the service and trying to help him all while acting like a douce, does not make you look like any less of a douce.
Being a douche huh? Well, I guess it comes down to the whole principal of things right? Isn't it a courteous kind of thing to reply to someone who needs a hand?
I think so. I don't see it as 25 people not responding because of a vague question. I see it as 25 people who don't know "how" or "want" to come up with any suggestions. Which brings me to my next point. Why have a forum in the first place, if all everyone is going to do is ignore each other. Its my fault really...shouldn't assume others would want to share their knowledge. Either way, thanks for chiming in, always love positive feedback 
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Verdad Gallardo Vague...guess that's why I created a post to begin with. Needed other ideas...area's to look at. Besides the basic essentials that we already went through. We will be checking compression, fuel pressure etc. As far as name dropping goes...trying to help a friend Being a douche huh? Well, I guess it comes down to the whole principal of things right? Isn't it a courteous kind of thing to reply to someone who needs a hand? I think so. I don't see it as 25 people not responding because of a vague question. I see it as 25 people who don't know "how" or "want" to come up with any suggestions. Which brings me to my next point. Why have a forum in the first place, if all everyone is going to do is ignore each other. Its my fault really...shouldn't assume others would want to share their knowledge. Either way, thanks for chiming in, always love positive feedback
Being a douche huh? Well, I guess it comes down to the whole principal of things right? Isn't it a courteous kind of thing to reply to someone who needs a hand? I think so. I don't see it as 25 people not responding because of a vague question. I see it as 25 people who don't know "how" or "want" to come up with any suggestions. Which brings me to my next point. Why have a forum in the first place, if all everyone is going to do is ignore each other. Its my fault really...shouldn't assume others would want to share their knowledge. Either way, thanks for chiming in, always love positive feedback Only a handful have the answers and the ones that do help, a lot of times people click the thread to read your post and learn from what you posted, some are just curious. So sometimes you are just going to have to be patient and realize that not all of LS1tech is full of GM engineers hiding their answers from you while laughing like mad men at your suffering.
You already had a list of things it could be that we would all tell you to check, but you didn't check them, so how in the world can we possibly help you? Do you part and then we can do ours.
Soooo have you checked any of that stuff yet?
