LLY: Need help...odd misfire at ~3,000rpm

[duratothemax]

Interesting.

Did you try swapping cam/crank sensors?

If the cam/crank sensors were swapped, it wouldnt even run at all. The thing is, my engine would run....it would just start to miss/sputter around 3,000rpm.

But just for grins I did put a CPS in the CKP position a few minutes ago. It would start and run, but barely...rattling/knocking etc...

Did you try a crank position relearn? .

there is no such thing on a duramax........


I ended up just cutting the sensor mount tab and using a washer on the bolt to re-clock the sensor. Yeah its ghetto and yes I would do this sort of thing to my own truck. There is no way in hell im going to go through the trouble of swapping front covers. Ill just run it like this, and if it shuts off on me while im driving sometime in the next couple days, oh well, its not like I wont know what the problem is.

Several pics. Of my unique front cover, the sensor in the "correct" position (well, 'correct' according to the cover, but in reality it wont start when its positioned this way), the sensor in the "wrong" position (but it starts/runs/revs fine with the sensor clocked here), and finally, my awesome fix.

ben

 

[SHOTZY]

Just finished reading this hole thread. After my build I had one hell of a time getting it to run. Btw they will run with the sensors swapped. I know this because mine did. Not well though. Would start shut off, start shut off. Then once I did this about a hundred times it actually puked its way to life. I actually was able to drive it. Next morning same sh*t. What our conclusion was that the heat from cranking caused the waves to align enough to run. Might be wrong on terminology there but you know what I mean. Now take a known cps and a known cks compare them, the clocking IS different. Now I'm not fimiliar with this front cover issue so I cant add anything there. But try swapping sensors. Good luck with this. I hate chasing this kind of sh*t.

 

[SHOTZY]

Just looked at your pics. IIRC the clocking should be straight up and down not rotated at all.

 

[DIESELMAFIAPER.LB7]

lol didnt read the second page gald to see you fixed it ben i deleted my comment

 

[duratothemax]

What our conclusion was that the heat from cranking caused the waves to align enough to run.

what heat is generated during cranking....?????

Now take a known cps and a known cks compare them, the clocking IS different.

Yes im aware of that.

But try swapping sensors.

I already tried that. It barely ran. If I had had the CKP and CPS sensors swapped for the past 6,000 miles there is NO WAY it would have run as well as it did. (it ran perfectly, up until ~3,000rpm where it would start to sputter/miss)

The conclusion/source of the problem here is that the front cover is apparently not a final-production piece. Its something else. Because production LB7/LLY CKP sensors do NOT have their tab/hole clocked correctly to work with the bolt hole in this particular front cover.

Im just going to run it like this until I finish getting the [second] built engine together. It runs just fine, right up smoothly to the rev limiter with my "elongated hole" and washer trick holding the CKP sensor in the front cover.....so I see no reason to mess with it.

Its going to be odd being able to floor it without sputtering and missing. Its been 6,000 miles and probably 8 months since my truck has completed a proper WOT upshift.

Now I just need to fix my bad front right wheel speed sensor to get rid of the ABS light thats been on for 6 months, figure out what the wailing/whooshing at high boost levels is (its not a boost leak, I think the turbo is on its way out) and OMG it will be like I have a brand new truck.

 

[Redbowties88]

is it possible that a medium duty could use a different ckp?

 

[duratothemax]

is it possible that a medium duty could use a different ckp?

no idea?

Someone (Johnny/gasuout??) will have to take a look at the picture of my front cover and confirm if, yes, its a medium duty cover, OR its something else.

I doubt the medium duty trucks use a different CKP sensor, but Ive definitely been wrong before.

 

[Redbowties88]

just thinking aloud, if so then it would be an easy fix as long as the kind of signals it sends are identical...

 

[JoshH]

If the cam/crank sensors were swapped, it wouldnt even run at all.

What is the difference between the cam and crank sensors? I thought it was just the way the tab was positioned? Maybe the cover you have is made so the same sensor could be used in both spots?

 

[Fingers]

The connector should be straight up and down.

You are missing the adapter plate that sits under the CKP sensor.

 

[duratothemax]

The connector should be straight up and down.

You are missing the adapter plate that sits under the CKP sensor.

ahh thats what I first thought too....but look closely...

On the normal 'production' front covers, when you remove the adapter plate, there is a much bigger hole (1"?) and two bolt holes. On this production covers, the adapter plate bolts to the front cover with 2 bolts, then the CKP sensor bolts to the adapter plate with 1 bolt.

If you remove the adapter plate on a production front cover, there is no way a CKP sensor will fit in it properly (and spaced out correctly)...this 'magic' cover I have was not designed to have an adapter plate.

 

[duratothemax]

see heres what a normal 'production version' LB7/LLY front cover looks like with the CKP sensor adapter plate removed.

 

[Fingers]

Just looked it up in the SI manual. The sensor is different for the medium duties. Note the connector orientation.

 

[duratothemax]

Just looked it up in the SI manual. The sensor is different for the medium duties. Note the connector orientation.

ah ha! Thanks for the picture. So apparently I have a medium duty cover. Who would have thought GM used a different style sensor on the medium duty trucks??? Doesnt make sense at all, from a cost-perspective...having two different sensors.

 

[SHOTZY]

what heat is generated during cranking....?????



Yes im aware of that.



I already tried that. It barely ran. If I had had the CKP and CPS sensors swapped for the past 6,000 miles there is NO WAY it would have run as well as it did. (it ran perfectly, up until ~3,000rpm where it would start to sputter/miss)

The conclusion/source of the problem here is that the front cover is apparently not a final-production piece. Its something else. Because production LB7/LLY CKP sensors do NOT have their tab/hole clocked correctly to work with the bolt hole in this particular front cover.

Im just going to run it like this until I finish getting the [second] built engine together. It runs just fine, right up smoothly to the rev limiter with my "elongated hole" and washer trick holding the CKP sensor in the front cover.....so I see no reason to mess with it.

Its going to be odd being able to floor it without sputtering and missing. Its been 6,000 miles and probably 8 months since my truck has completed a proper WOT upshift.

Now I just need to fix my bad front right wheel speed sensor to get rid of the ABS light thats been on for 6 months, figure out what the wailing/whooshing at high boost levels is (its not a boost leak, I think the turbo is on its way out) and OMG it will be like I have a brand new truck.

The heat was generated when it started and shut off. 10 minutes of this and it will get hot. Sorry didn't see where you swapped them. Glad you got it figured out.

 

[HEEPJEEP]

ah ha! Thanks for the picture. So apparently I have a medium duty cover. Who would have thought GM used a different style sensor on the medium duty trucks??? Doesnt make sense at all, from a cost-perspective...having two different sensors.

Fawking engineers....

 

[duratothemax]

Fawking engineers....

blow up.