Single engine knock when cranking

[Stalker L-67]

When starting the 2004, L67 engine in a kit car with a 1999 Pontiac GTP computer about half the time I get one loud knock when starting/cranking. I have looked but am unable to find the timing table for cranking/starting. I am sure somebody here knows where it is. I probably have looked at it many times but did not know what I was looking at. Oh, and yes the engine starts just fine other that the knock.

Thanks!
Scott

[murphinator]

one knock when cranking doesnt sound like a timing issue , mechanical maybe ?

as far as timing on a L67 under engine> spark control>spark advance

you have your high and low octane timing tables along with a couple spark correction tables


on a cold start your engine coolant temp correction table wouldnt be changing your timing only if you are getting into the mid to high cyl airmass would it start adding timing when cold - shouldnt affect it when cranking ? unless someone has changed the correction table at low rpm's to add timing ?

those L67 stalkers look like a lot of fun btw

[Stalker L-67]

It is definately engine knock I have heard it on other engines. I real nice "PINK" and then the engine starts just fine.

IAT spark table set to all "0".....Not my doing....... Might have to change this I just read that 10 degrees F = .5 octane.

AFR correction
8 deg @ 9.5:1
6 deg @ 10.5:1
5 deg @ 11.5:1

ECT timing does not come into play until below 32F

[murphinator]

have you tried saving your tune and pulling timing from say 1200 rpm down then to see if you can get rid of it with timing ? if it doesnt work just put the saved tune back in.

where this is a kit car that I am making an assumption you just got together what is in it for fuel since knock usually is due to timing or poor octane

you didnt put the year old lawnmower gas in it so you could finally hear it turn over did you

[IndeedSS]

You have not missed the startup timing tables because we don't have access to them. Apparently the cells in the Main table does not control the initial timing.

[bilemke]

You have not missed the startup timing tables because we don't have access to them. Apparently the cells in the Main table does not control the initial timing.

Yeah, there are separate fueling tables too.

[IndeedSS]

Yeah, there are separate fueling tables too.

Here we go again. Now all wee need is for Eddie to show up and post a picture of said table, so we can see what we can't access

[murphinator]

ok beyond all the "classified " "top secret" tables

what advice can we give the original poster to make his start up knock go away

[IndeedSS]

So it's one loud, as in audible, knock or ping? Is this only on cold startup? Can you get a scan of the startup? I'm sure you know how to do this, but when I scan startup, I make sure the key is in the on position, scanner is "Connected" and scanning then turn the engine over.

[GTPNoga]

I get this on my GTP engine sometimes. When the enigne is cold you might hear the wrist pins "rattle" once and thats it. Also check your flex plate to make sure it's not cracked too.

[Stalker L-67]

"So it's one loud, as in audible, knock or ping? Is this only on cold startup?"

Yes, that's it, now that I think about it, its probably about 5% of the time.

Good idea on scanning the start up, will do this during the week. Spent most of the day at a AutoX and am toasted........yes it was 77 and sunny all day with a slight breeze..........how is your winter going?

No flex plate! Flywheel hooked up to a T5.

Scott

[IndeedSS]

77 degrees and sunny? It was 0 here a few days ago and didn't even make 30 today.

[GTPNoga]

I don't think it's anything tune related. There might be a rod bearing that is out of spec and depending on what stroke it's in when the engine is turned off will make it seem like only 5% of the time it's happening.