Coil#4,6,7 NO FIRE! Crank Sensor? Reluctor Wheel? Tech Guru's Inside!!!
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Coil#4,6,7 NO FIRE! Crank Sensor? Reluctor Wheel? Tech Guru's Inside!!!
I don't know what in the hell is going on here so maybe someone else has an idea.. Cranked the car (408 lsx '98 pcm/harness) and it runs, but runs like total crap. So we checked all the coils.. #4, 5 & 7 there is ZERO Fire.. So we swap all of the coils over to another set of coil brackets with different wiring and still the same thing.. So we swap coils with my '07 silverado and still the same thing.. I get another '98 computer and swap it and still the same freakin thing. So we break out the multi-tester and start checking the wires. Every coil has a HOT wire and every one of them is HOT.. Every coil has a ground wire and they are all grounded. So we check the signal wires from the computer to the coils. The dead coils did nothing when we spun the engine over. The coils that were firing would jump up immediately on the scanner. We checked all of the wires for "continuity" and that checked out great. We then checked the signal wire at the pcm and it was dead as hell just like it is on the other end at the coil itself. So we are pretty sure that the computer, wiring harness and the coils are all in perfect working order.
Could this be the crank sensor?? If the crank sensor is bad would any of the coils fire? I always assumed that when the crank sensor went bad it wouldn't fire any of the coils.
I am also leaning towards it being a problem with the reluctor wheel on the crankshaft. This crank was repaired and the wheel was removed and re-installed after being repaired. Does this sound like the problem? If so then my only choices are pulling the engine out and taking it apart completely to have the wheel fixed or to put a carb/distributor on it and call it a day like I should have done from the beginning.
The only thing I have changed with this setup since it ran a year ago is changed from relocated ls1 coils back to valve cover mounted TRUCK coils and I had the crank repaired which required them removing the reluctor wheel and freshened the engine.
PLEASE somebody with some knowledge in this area help me out here!!! If it could possibly be the crank sensor then I will swap it with an extra that I have. But I just figured that a crank sensor goes bad and doesn't just half *** work. Any and all help is appreciated..
--Matt
Could this be the crank sensor?? If the crank sensor is bad would any of the coils fire? I always assumed that when the crank sensor went bad it wouldn't fire any of the coils.
I am also leaning towards it being a problem with the reluctor wheel on the crankshaft. This crank was repaired and the wheel was removed and re-installed after being repaired. Does this sound like the problem? If so then my only choices are pulling the engine out and taking it apart completely to have the wheel fixed or to put a carb/distributor on it and call it a day like I should have done from the beginning.
The only thing I have changed with this setup since it ran a year ago is changed from relocated ls1 coils back to valve cover mounted TRUCK coils and I had the crank repaired which required them removing the reluctor wheel and freshened the engine.
PLEASE somebody with some knowledge in this area help me out here!!! If it could possibly be the crank sensor then I will swap it with an extra that I have. But I just figured that a crank sensor goes bad and doesn't just half *** work. Any and all help is appreciated..
--Matt
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sounds like you guys did just about every test you can do. I think you may have it narrowed down to that reluctor wheel on the back of the crank. Pull the oil pan and see if any of them are bent or damaged.
#4
I think this may be a cam position sensor problem. That has more say into when cylinders actually fire than the CKP sensor does, since it knows what stroke the engine's on. So check into that too.
And I don't think the car would fire up if the CKP sensor was bad, unless like you said only certain teeth on the wheel are bad.
Do you have access to a scope so you can see what kind of signals the two sensors are putting out, that would help you out a lot.
And I don't think the car would fire up if the CKP sensor was bad, unless like you said only certain teeth on the wheel are bad.
Do you have access to a scope so you can see what kind of signals the two sensors are putting out, that would help you out a lot.
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We are gonna use a TECH II tool on it later this week and see what kind of signal the crank sensor is putting out.. Hopefully that will tell me something..
#6
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I had a horrible problem on a brand new ls1 conversion I did and had misfires and ran like total crap. After changing everything possible including wiring harnesses and pcm, I ran a "crank relearn" in HPTuners. It would barely even run well enough to do it but as soon as i did *BOOM* instantly ran perfect and fixed all the horrible problems with misfires and dead cylinders and barely running...
Try a crank relearn
Try a crank relearn
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Thanks that sounds like a good idea, but I don't think I can get it to run long enough to do it.. The only way it will run now is if you hold the rpms up around 2500 or so and I HATE doing that with it running this rough..
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I kinda thought I would get a little more help than this from all the techies, but I guess not. I changed the crank sensor and it did nothing different. We did realize that its only the #4 and #7 coil that isn't firing.. All of the other coils work fine. So we are pretty much pointing our fingers at the reluctor wheel..
Obviously thats the only thing left to blame.. Apparently the crankshaft repair specialists have fucked my engine up and now I'm left with a very nice EFI setup that I can't even use due to someone else's screw up. Whats new about that.. This engine has been a nightmare from the beginning. Bought it from a sorry M'Fer that was suppose to be trust worthy on this board and ended up being a worn out piece of **** and after a year of getting it all fixed and straightened out this is what stems from that...
Anybody got a bullet they don't mind me eating??
Obviously thats the only thing left to blame.. Apparently the crankshaft repair specialists have fucked my engine up and now I'm left with a very nice EFI setup that I can't even use due to someone else's screw up. Whats new about that.. This engine has been a nightmare from the beginning. Bought it from a sorry M'Fer that was suppose to be trust worthy on this board and ended up being a worn out piece of **** and after a year of getting it all fixed and straightened out this is what stems from that...
Anybody got a bullet they don't mind me eating??
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I haven't done that yet, but it is on the agenda before I do anything with the motor.. I don't have anybody local to come to my house and do anything with HP Tuners. As soon as I get somebody over here we are gonna try that, but its gonna be hard to keep the engine running while we do it..
If that doesn't work then I am out of options.. I'll be pulling the computer, harness and the intake/tb setup that I have grown to like so much and trading it all for a distributor and carb and calling it a day..
#13
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We've seen where 1,4,6,and 7 would be the only ones firing (or the opposite cylinders). It ended up being the reluctor wheel installed backwards on the crankshaft. Shoot me a PM if I can help you figure it out!
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I think this may be a cam position sensor problem. That has more say into when cylinders actually fire than the CKP sensor does, since it knows what stroke the engine's on. So check into that too.
And I don't think the car would fire up if the CKP sensor was bad, unless like you said only certain teeth on the wheel are bad.
Do you have access to a scope so you can see what kind of signals the two sensors are putting out, that would help you out a lot.
And I don't think the car would fire up if the CKP sensor was bad, unless like you said only certain teeth on the wheel are bad.
Do you have access to a scope so you can see what kind of signals the two sensors are putting out, that would help you out a lot.
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Thanks man I'll definitely get with you about this if we can't figure it out this week. my buddy is gonna bring his TechII over tonight or tomorrow hopefully and we are gonna check the cam and crank sensor to see what kinda signal they are putting out.. Appreciate the help..
#18
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Yea, when we looked at one that had the wheel on wrong, it had strong and steady signal IIRC, but it was the wrong signal all together and the PCM was freaking out.
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And I am positive that the only coils not firing is 4 and 7..