LMM and P0336

jraymer

<--Tree Hugger
Oct 31, 2008
1,421
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Las Vegas, NV
Well some of you may remember me, so not, but after a 6 year so absence from forums I am back and in need of some ideas/fresh eyes.
I have been working on /diagnosing an LMM for the past few weeks and am at a loss. I installed an HSP twin kit almost a year ago and all went well truck ran great. Then about a month ago the truck was studded/gaskets and 30% nozzles installed. After that job truck was great and drove fine. The coworker that performed the head gasket and stud job had a valve cover leak on the passenger side. So he pulled it apart, fixed leak but ever since then there started the P0336 code and at times it will also throw 8 misfire codes, 90% of the time only the P0336 code will set.

The code will come on startup. Usually when hot while cranking, the truck will almost sound like is has bad fuel knock a couple times but then clear up within seconds and idle/run smooth. Sometimes times hot it won't knock at all and fire up just fine. I can drive the truck 40 miles with no codes and the truck running great, but once shut off and restarted, it will knock and knock and then start and idle fine and the code will be there.

Things I have done:
swapped cam and crank sensors.
Checked reluctor wheel, seems tight.
Crank is not broken.
tested crank sensor wiring.
Even made a new harness from crank sensor to ecm.
Swapped ECM's with another truck.
All of this stuff done with no change.
So I am here hoping some of you guys may have some ideas as I am at a loss.
Could an overfilling injector cause these issues? Or will bad cam sensor wiring cause a p0336 code or I would think it would be a different code.
Sorry for the long post.

Thanks!
 

Chevy1925

don't know sh!t about IFS
Staff member
Oct 21, 2009
21,171
4,955
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Phoenix Az
Welcome back Justin :hug: :D

are you sure the crank has not broke in a different spot besides the normal "behind the first main"? may have to throw a bar on the balancer and have someone listen to the oil pan as you rock the crank back and forth
 

jraymer

<--Tree Hugger
Oct 31, 2008
1,421
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Las Vegas, NV
He followed me...
Yea I will check the crank. It's just weird that it drives so well other than the code on startup. Freeway ripping and 30psi boost and all.
 

Chevy1925

don't know sh!t about IFS
Staff member
Oct 21, 2009
21,171
4,955
113
Phoenix Az
i dont remember who it was but there was someone on here that broke their crank back by main number 4 (might have been dale "LBZ") and it drive fine other than some codes it was throwing. only way he knew it was the crank was when they twisted the balancer back and forth and heard the clanking. but thats just off memory and it was a long time ago....
 

jraymer

<--Tree Hugger
Oct 31, 2008
1,421
0
0
Las Vegas, NV
Thanks Tom, yea it has been a bit for sure. Being around this stuff everyday got me a little jaded. As for this LMM, I haven't touched it. maybe next week I will poke around at it a bit.