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Back home let it idle more and seems to be clearing out, initial hiccup when cold start. I let it warm up then pulled out at the light got some light misfires that started and stopped.By the time I got home it stopped and let it idle and had a couple then stopped. Feeling optimistic
Get rid of the stock thermostat. Running way too hot for a performance engine. A 180 or 187 should make it happier. Have you added the coolant cross over to the rear of the heads?
Get rid of the stock thermostat. Running way too hot for a performance engine. A 180 or 187 should make it happier. Have you added the coolant cross over to the rear of the heads?
Get rid of the stock thermostat. Running way too hot for a performance engine. A 180 or 187 should make it happier. Have you added the coolant cross over to the rear of the heads?
The temps seems to stay higher after I changed my water pump a few months back
May have to get a gm pump not aftermarket
Had the OEM t stay in there too but it went from 190 to 210 f but that's a separate issue I guess
No rear ones there not drilled out on the head
It's definitely improved from at first but is still behaving erratic and inconsistent with the faults.
Registers about a 100 random misfires (mainly 1,4 and 7) in the first 15 seconds of running then clearing out as it idles
When decelerating it might buck then misfire but might or clear on its own or with a rev.
Let from lunch and it missed in start up and the light came on (first since putting pushrods,) I cleared it and the counts seemed to stop.Drove a few blocks it did it again , I got on the go pedal a quick rip and the let it idle and seemed to have little to no counts.
When to park as a slowed for the dip to pull in there was a flare of misfires about 60 then parked and idled. The idling cleared out the register misfire counts.
Maybe some junk or debris in the lifter or just defective lifters?
What if it's just carbon on the valves that did seat due to longer pushrods?
Stock is 195f or 91c . The first chart he showed 214 deg.. keeps emissions low along with performance. And increase knocking.
True but 214 isnt over heating on LS engines
Although it is warmer than normal it's not my issue
Cylinder that seem to misfire are 1,4 and 7 only
Linear to the former dod system
If it was knocking there would be counts on all.
Drove home started up had a few but as it idled they cleared out and history counts went back to 0
By the time I got home it had less than 100 counts with idling the history counter cleared and there were a few stray counts on 1 and 7 but less than 10.
Might add the rest off the marvel oil get it warm and change the oil.
Last edited by BJammin92; Dec 2, 2025 at 09:32 PM.
Did another slight stumble miss when pulling in. Pulled up the driveway aggressive when stopping suddenly it surged a little then smoothened out and cleared out the counts on its own. A few hair counts.
Lil by little improving. Cleared it self out idling in driveway
It’s looking more like a tuning issue than a mechanical problem. Or a vacuum leak, causing the tune to be off. Can you add the fuel/air ratio to your scan? And fuel pressure?
Could it be the plugs you put in the AFM tower are leaking on those cylinders? You have solid well know parts. It should just work.
It’s looking more like a tuning issue than a mechanical problem. Or a vacuum leak, causing the tune to be off. Can you add the fuel/air ratio to your scan? And fuel pressure?
Could it be the plugs you put in the AFM tower are leaking on those cylinders? You have solid well know parts. It should just work.
I believe if I had a tune or leak it would affect all cylinders equally right? Not 3 specific cylinders.
I feel those are sealed air tight. Plus the ls3 valley cover the o rings would seal any seepage if any.
I don't have a afr gauge installed.
I'll log a longer drive this weekend and send it to the tuner
I had to stop when tuning as the misfiring was significant in the beginning.
Not tune related, did oil change and ran it a few days. Now light is flashing occasionally. Stopped running it.
Compression test on good cylinder was 200 psi on the first whirl
#1 was 125 psi
Ran this scenario thru gpt , said possible bad lifters loosen the rocker one half turn and recheck compression
Loosened half turn and compression jumped to 210 psi
So ordered some morel 7717 lifters along with new trays, supposed to be the quality choice.
Either way I pulled the pushrods , cranked it over , reinstalled and compression went to 150 psi. Definitely funky lifters especially when I pulled the pushrods and cranked the engine, let it sit overnight and then #6 stopped misfiring and never gave a issue since.
Lifters here Wednesday and will get on it this weekend.
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