Knock, Knock, Knocking on heavens door!

[EagleMark]

Well that's all I get with this new built cammed 5.3L 2000 LS engine. Even with a flushed tank on high octane fuel it's pulling 8* timing at WOT and pulling some timing even if not at WOT.

The knock sensor were replaced along with the harness from them during the rebuild because they were oil soaked and nasty.

Can't hear a ping. Even with Low Octane table it's pulling timing. Motor is a quite as could be.

Any ideas on how to diagnose them, things that could be done wrong, did we get some bad AC/Delco knock sensors, etc... any ideas. We've done all the regular stuff like looking for something loose or rattling...

[Fast355]

Well that's all I get with this new built cammed 5.3L 2000 LS engine. Even with a flushed tank on high octane fuel it's pulling 8* timing at WOT and pulling some timing even if not at WOT.

The knock sensor were replaced along with the harness from them during the rebuild because they were oil soaked and nasty.

Can't hear a ping. Even with Low Octane table it's pulling timing. Motor is a quite as could be.

Any ideas on how to diagnose them, things that could be done wrong, did we get some bad AC/Delco knock sensors, etc... any ideas. We've done all the regular stuff like looking for something loose or rattling...

Did you torque the sensors? IiRC the LS sensors are torqued a bit differently than the old 350s.

When I 0411 swapped my Express was showing knock like crazy. I have had knock retard turned completely off for over a year.

[brian617]

Are the rockers audible? I know a guy who gave up on aftermarket cams in favor of a GM cam because of all the noise he was getting. Even tried different length push rods recommended by the cam manufacture.

[EagleMark]

No, it's as quite as can be and the cam is in mild range. I've listened to everything my self from under hood to bottom of engine on a lift and we even brake/loaded the engine till the wheels spun. There's no noise. Motor was pro built and installed by owner of the repair shop so it's been gone over well. We're just scratching our heads with the knock?

Fuel was even checked yesterday...

[dave w]

I think it's too much oil in the combustion chamber. Check the plugs? How does the oil smell, gasoline ordor? To much oil in the combustion chamber will "rock" the piston around at / or near TDC.

dave w

[Fast355]

I think it's too much oil in the combustion chamber. Check the plugs? How does the oil smell, gasoline ordor? To much oil in the combustion chamber will "rock" the piston around at / or near TDC.

dave w

Might be onto something Dave. Does the engine have the newer design fixed orifice PCV valve?

[mecanicman]

How much timing we talking wot? What afr you at?

[Fast355]

How much timing we talking wot? What afr you at?

Also a valid point, but it seems as if he is trying to run the stock low octane map and there is not much timing there. The last 4.8 I tuned only used 28* of total timing at WOT.

[mecanicman]

Also a valid point, but it seems as if he is trying to run the stock low octane map and there is not much timing there. The last 4.8 I tuned only used 28* of total timing at WOT.

You must have better fuel, stuff out of the pumps here I usually end up more like 24-26

[steveo]

i helped tune a 5.3 the other day. they really dont seem to like (or require) a bunch of timing, probably because they have a pretty damn efficient combustion chamber. 28 degrees wot all-in is sooo much for that engine imo

[Fast355]

You must have better fuel, stuff out of the pumps here I usually end up more like 24-26


i helped tune a 5.3 the other day. they really dont seem to like (or require) a bunch of timing, probably because they have a pretty damn efficient combustion chamber. 28 degrees wot all-in is sooo much for that engine imo

Shell/Chevron 93 is the only thing I recomeend people around here to use. Well E85 is better in a Flex Fuel.

The truck I tuned was 4.8 with milled ported 243s in a RCSB truck.

The 5.3s I have tuned are as you guys have said 24-26* total. I think the short stroke/long rod makes the 4.8 want a little more timing.

The old L31 engines do not like a whole lot of timing with the stock cams either.

[Fast355]

We did however recently have some kind of gasoline reformulation. I had been running 89 octane, KNOCK FREE on 32-33* total timing in my Titan. Suddenly it was picking up knock activity at WOT, no actual timing retard yet though. Nothing more than a few months time and a noticeable change in gasoline quality. Computer even picked up the change and adjusted the ethanol % accordingly. I am thinking we are getting more than 10% in most batches here. I am glad that I logged it, moved up to 93 octane and retarded the timing 2*, before I hit it with the 75 shot.

[brian617]

I am thinking we are getting more than 10% in most batches here.

Buddy at Chevrolet dealer said he tested a truck with 14% recently (Walmart/Murphy station).

[EagleMark]

I'd have to look at the calibration but it is the stock High Octane table timing... by rights it should not be knocking, on stock motors that have been running high octane I've seen no knock retard to 1*. At one point in a log it was only getting 10* and pulling 8* timing.

The GM.ASPARK PID is still at 70% as well, so thats 70% High Octane and 30% low octane table for spark advance. Don't think the knock sensors were over tightened, the owner of the rig is a certified tech and owner of the shop as well as aware of knock sensors being sensitive to torque. He checked today and the were not AC/Delco but Delphi replacement sensors.

AFR is about 12.5, I've set it up VIA EQ Ratio at 1.16.

The oil is interesting! We'll be pulling plugs tomorrow for a look. This is a brand new motor and maybe 500 miles on it. No notice of any oil burning or loss. Also going to try turning off the knock sensors and see if they are the issue...

[ony]

maybe plugs to hot?

[EagleMark]

UPDATE: Pulled the intake manifold and replaced the knock sensors over the weekend.... damit.... no change!

We've been waiting for the engine builder as he was gone on vacation last week. Find out he's using a Delta cam? Anyway they grind there own and he's used a lot without issue. They are just ground to whatever specs and this one is a Comp Cam (get cam specs... I've seen them and it's like a .214 and .218 @ .050 with a 114 lobe center) nothing radical and a good truck cam. But for some reason he's been grinding a lot off the bottom and reminded him that it needed longer pushrods, like .025 longer and that should quite down the valvetrain noise. It's a little noiser if you have a stock engine running next to it and can go back and forth to listen or you'd never notice it. So waiting for them to change and check again...

Then I'm reading some archive threads about some of these 1999 and 2000 truck OS and engine cals and seems there are a bunch that are just over sensitive and pull timing! There was a whole slew of dog slow trucks out there and I guess still is! All are about the same too, up to 8* knock retard timing. Just some? Not all? And no where did I see OS or Engine Cal number mentioned? So who knows?

But the cure to all of them is to upgrade to a 2002 OS 12212156. I guess I should have known better and just started there. Hopefully most of the work I did data logging and adjusting the VE, then MAF and also did the IAC logs so it's got a good cold/hot start was not a waste of time. Building a new cal for it today so I'll be ready if it's still doing the Knock Retard thing after the pushrod change!

[brian617]

UPDATE: Pulled the intake manifold and replaced the knock sensors over the weekend.... damit.... no change!

We've been waiting for the engine builder as he was gone on vacation last week. Find out he's using a Delta cam? Anyway they grind there own and he's used a lot without issue. They are just ground to whatever specs and this one is a Comp Cam (get cam specs... I've seen them and it's like a .214 and .218 @ .050 with a 114 lobe center) nothing radical and a good truck cam. But for some reason he's been grinding a lot off the bottom and reminded him that it needed longer pushrods, like .025 longer and that should quite down the valvetrain noise. It's a little noiser if you have a stock engine running next to it and can go back and forth to listen or you'd never notice it. So waiting for them to change and check again...

Thats the same problem my buddy ran into. Non adjustable rockers, ground base = longer pushrods. Even then the way the ramps on the cam are ground can still affect how audible the valve train is. He was using a mild Comp cam grind.

[Skinny Pedal]

Where is the timing reduction coming from? Knock, torque reduction, burst, trans............ Also, be sure the octane scaler isn't automatically hitting the percentage you gave based on the tune. I've chased similar before and it ended up being a combo of different timing reduction requests.

[mecanicman]

All aftermarket cams are ground on a smaller base circle, sure its so they can sell you pushrods. I have chased that as knock once before, might be gone when they are correct length. I would try throwing fresh gas at it as well, different source.

[steveo]

All aftermarket cams are ground on a smaller base circle

that's a completely false statement.

[EagleMark]

Where is the timing reduction coming from? Knock, torque reduction, burst, trans............ Also, be sure the octane scaler isn't automatically hitting the percentage you gave based on the tune. I've chased similar before and it ended up being a combo of different timing reduction requests.All torque management is off except for gear changes. Burst knock was off. The retard showing in the log always pulled GM.ASPARK PID %. So pretty sure it was knock retard... but that's a good point and should look further.

With the engine builder admitting the push rods need to be longer and it won't be as noisy and the finding of the 99-00 Truck Knock issue I think we have an answer....

[mecanicman]

that's a completely false statement.
Ok, all aftermarket ls1 cams I have installed(should have included ls1 in first statement) have had a smaller base circle. Curious which ones do not ?

[Fast355]

Ok, all aftermarket ls1 cams I have installed(should have included ls1 in first statement) have had a smaller base circle. Curious which ones do not ?

The Comp cams for the modern Hemi engines are the same. They use the smaller base circle of the 6.1.

[EagleMark]

It's fixed! Installed the 12212156 OS from same 2002 GMT800 truck and copying all the tune work over to it, was still within 8% on fueling, I had it within 3%. Added 2* timing to the pull and cruise areas and not a bit of knock retard!! :jfj: Truck sure pulled better! :jfj:

Checking the log it was only getting 20* at WOT so going to raise that up a bit to 24*.

Push rods showed up when I was done and they are still going in but we know now it was not noise, it was one of the 99-00 OS Engine cals that suck. Truck drives overall much better!

[dave w]

Thanks for the update!:thumbsup:

Question / Question / Question so what about using the 12212156 OS in the 09354896 PCM??? I've read it's not a good idea to install an '0411 OS into a 09354896 PCM.

dave w

[mecanicman]

Thanks for the update!:thumbsup:

Question / Question / Question so what about using the 12212156 OS in the 09354896 (tel:09354896) PCM??? I've read it's not a good idea to install an '0411 OS into a 09354896 (tel:09354896) PCM.

dave w

Same PCM as 0411, different service number. My 99 Sierra runs 09354896 with 12212156 no problem

[EagleMark]

Nice! Wonder how many other PCMs can be used in place of the 0411 ?

[84Elky]

Reply deleted due to fix not previously noted.

[1BadAction]

I know you've "fixed" it, but what do your IATs look like? Some cals are terrible about pulling timing vs air temps, I'd look into that also to see whats going on.

[EagleMark]

Well since it was in 60's and raining yesterday I had no IAT issues... when it was pulling timing it was warmer days but I had zeroed that table out wondering if it was a cause? It is back to stock now.