lm7 p0300 random misfire need help
11-17-2016, 06:25 AM
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lm7 p0300 random misfire need help I recently installed a 5.3 in my 02 Avalanche . I put 799 heads with beehive springs new gm lifters and a 212 / 218 cam and new chain set and high flow oil pump . I first started it up had misfire cyl #2 . then after that came up random each time . came with a cracked #8 coil but I swapped that one . anything I swap from my old engine worked with no check engine lights at all so I know they functioned correctly. I'm trying to sort this out quickly because it's my daily. and its going to get colder here in Jersey soon
So far I checked for vaccume leaks ,
heard every injector clicking and checked they were connected (clicked on )
rechecked torque on intake .
I'm going to pull plugs again today and check and gap.
check wires too both plugs and wires are new
I was thinking I heard somthing about cam sensor seeing I upgraded heads and cam
I have a few things to sort out still like shim starter , change tranny lines . I knicked one grinding off exhaust stud . replace cheap autozone exhaust studs (again)
Any help I greatly appreciated and I thank you in advance
So far I checked for vaccume leaks ,
heard every injector clicking and checked they were connected (clicked on )
rechecked torque on intake .
I'm going to pull plugs again today and check and gap.
check wires too both plugs and wires are new
I was thinking I heard somthing about cam sensor seeing I upgraded heads and cam
I have a few things to sort out still like shim starter , change tranny lines . I knicked one grinding off exhaust stud . replace cheap autozone exhaust studs (again)
Any help I greatly appreciated and I thank you in advance
11-17-2016, 10:24 AM
#2
If it is a completely different engine than what was originally paired up with the PCM then you need to do a CASE relearn. Also called a Crank Sensor relearn. Cam sensor has nothing to do with causing or detecting misfires. That cam could also be causing the stock misfire calibration in the PCM to be detecting false misfires.
11-17-2016, 08:22 PM
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I will look into that right now .I dropped off at the tranny shop tonight to replace both tranny cooler lines and noticed the check engine light went off . cant remember if I erased code or not . I did erase a few times maybe I get lucky . I doubt it , Either way I'm almost there . I actually impressed myself on this job . I'm a part changer not a mechanic I did learn don't mess with your daily driver. I was almost heart broken when at one point I wanted to give up , Wasn't sure last Saturday if I was buying a new truck or not . It wasn't about the money it was that I took a truck I love tried to make it better and the thought of it going to the junkyard and that I killed it was really beating me up . My wife said cant you take it to a shop ? I said no, noone will touch this , wires all over everything all apart . whew I kept thinking I can't count on any help, Im on my own and dont want to let myself down
11-20-2016, 02:13 PM
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its the same engine from a 5.3 02 chevy avalanche . I took a nice 40 mile ride CE light went off ran smooth there then on way home after stop for 3 hrs at my Moms upon restart to drive home CE came back on , when I got home I read codes again and p0300 came back and also p0102 so I changed coil packs to origional engines coil packs that did run fine on origional engine cycled key 50 times codes still come up . Truck will be driving to work tomorrow. up for suggestions
11-22-2016, 06:26 AM
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no its the same converter .installed 41-962 plugs dropped one cant find it. got 41-110 irridiums on the way gonna check the ground by mass air flow possibly replace other 7 injectors already replaced #2 injector compression is good , new valve job
recap .... replaced lm7 with exact lm7 my ecu 799 heads with beehive springs , 212 218 cam . everything ran fine before swap no ce lights no mis no P0300 no p0102 . compression good valve job done by reputable shop nicks machine South River N.J.
anything I take off old engine should be fine .I put a half bottle of seafoam in the tank seems like a very mild misfire but to me a misfire is a misfire . She holds Idle I just don't want to take it to the stealership so they can throw parts at it and walk out with the same miss 1500.00 later after I did all the hard work
recap .... replaced lm7 with exact lm7 my ecu 799 heads with beehive springs , 212 218 cam . everything ran fine before swap no ce lights no mis no P0300 no p0102 . compression good valve job done by reputable shop nicks machine South River N.J.
anything I take off old engine should be fine .I put a half bottle of seafoam in the tank seems like a very mild misfire but to me a misfire is a misfire . She holds Idle I just don't want to take it to the stealership so they can throw parts at it and walk out with the same miss 1500.00 later after I did all the hard work
11-22-2016, 10:10 AM
#7
If it is a completely different engine than what was originally paired up with the PCM then you need to do a CASE relearn. Also called a Crank Sensor relearn. Cam sensor has nothing to do with causing or detecting misfires. That cam could also be causing the stock misfire calibration in the PCM to be detecting false misfires.
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11-22-2016, 10:24 PM
#9
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Jimmy: 2xLS1 is saying that your PCM needs to be tuned to have the misfire tables adjusted (desensitized). Any tuner should know how to do that. Who tuned for your cam? That person/service should be able to handle it.
The CASE relearn is a completely different thing, although someone with e.g. HP Tuners could do both. The CASE relearn is performed with an appropriate scanner in the car with the engine running and car drivable.
The CASE relearn is a completely different thing, although someone with e.g. HP Tuners could do both. The CASE relearn is performed with an appropriate scanner in the car with the engine running and car drivable.
11-22-2016, 10:36 PM
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It runs and drives . I made an appointment next week at dealer to diagnose and crank relearn . I put in cam myself I put longblock together myself . I guess I will have to have it tuned afterwards. Damn . But thank you I appreciate you gentlemen helping me .
11-27-2016, 10:05 PM
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12-08-2016, 03:30 PM
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Well she's all done . 262 dynoed to the wheels.3 sumthing . I guess I built a slug . They had problems connecting to tuning software due to the idiot I let hook up my aftermarket stereo to wrong wire . I pick it up tomm. Price was fair at tune time 700+ considering rewire stereo. They are ok with me .
It was my first build just messing around .
It was my first build just messing around .
12-08-2016, 04:00 PM
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Good to hear.
I'm confident everything you learned in the process is priceless.
Thank you for updating the thread; when people forget to post the result, it is frustrating to those who tried to help.
I'm confident everything you learned in the process is priceless.
Thank you for updating the thread; when people forget to post the result, it is frustrating to those who tried to help.
12-09-2016, 04:44 PM
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Yes lugnut. I can build an engine . I'm happy with it she runs strong now my avalanche got a new lease on life . Still probably cheaper than getting a 5.3 longblock replaced at shop . Thank you for the help and confidence