Timing ...help!! 94 k1500, 5.7, $OD, 7427

[BigBanks78]

My dad was reading about a corvette with stock roller rocker arms had to make some knock sensors that were less sensitive so they wouldn't pick up rocker arm noise.

Notsaying thats your problem just that if you pull timing and you still have same knock go over mechanicals!!

i keep having software problems that turn out to be mechanical :-)

[dispoejoe95]

Big....It is certainly worth looking into.

Btw, Brian, I double checked and I have already made those changes for eliminating the EGR. I thought I had...I'm sure I read to do it on a thread somewhere in this forum.

Thanks for the suggestions guys.

[sturgillbd]

I would make sure the exhaust isn't rattling or rubbing against the frame etc. I would also make sure I wasn't running lean. If vehicle is in PE mode, you really need a wideband to know what your afr actually is.

[dud]

I have pretty much the same setup and the only difference with my problem was that I could actually hear
pinging.I turned off "Altitude Spark Bias" and the problem went away. Couldn't hurt to try. I found the answer
In this thread;
http://www.gearhead-efi.com/Fuel-Inj...=altitude+bias

[dispoejoe95]

I'm going to have to read that a few times to grasp it all...but i will try that and see what happens. Thanks!

I may have another issue though. Looking at my spark advance in my latest data log in Tuner Pro and I have 13 cells where the timing shows at over (I kid you not) 23000 degrees!! This has got to be a glitch but I'm not sure what's going on...maybe a bad ECM or distributor perhaps. I noticed this in one or two cells in past logs but didn't think much of it....but now in 13 cells, I have a growing problem! See attached, I copied the "running maximum" spreadsheet. Anyone seen this before?

[dispoejoe95]

So I looked at my spark advance table from my last datalog run and compared it to my timing table in my bin and it is approx. 10° off. Thinking "how could I have missed this before" I played back some older datalogs and my timing was right where it should have been. Long story short, I found that when I had unchecked or un-set backpressure EGR about a week or so back is when the timing table in my datalogs lost the 10°. I'm not exactly sure how they are tied together but the parameter comments on Altitude Spark Bias say "used with back pressure EGR". Maybe doing both (un set backpressure EGR and correcting spark bias) will eliminate my knock count issue. I'll try it this week along with a few other suggestions.

Also, if anyone is interested, in the cells where my timing says 23039°...I think this is where the timing is supposed to be a negative. Again, not exactly sure why it shows +23000...I'll need to figure this out next.

Thanks again for the help guys.

[Fast355]

So I looked at my spark advance table from my last datalog run and compared it to my timing table in my bin and it is approx. 10° off. Thinking "how could I have missed this before" I played back some older datalogs and my timing was right where it should have been. Long story short, I found that when I had unchecked or un-set backpressure EGR about a week or so back is when the timing table in my datalogs lost the 10°. I'm not exactly sure how they are tied together but the parameter comments on Altitude Spark Bias say "used with back pressure EGR". Maybe doing both (un set backpressure EGR and correcting spark bias) will eliminate my knock count issue. I'll try it this week along with a few other suggestions.

Also, if anyone is interested, in the cells where my timing says 23039°...I think this is where the timing is supposed to be a negative. Again, not exactly sure why it shows +23000...I'll need to figure this out next.

Thanks again for the help guys.

Really not sure why you would ever have negative timing with Vortec heads. The minimum value in my timing table is 12-16° on everythimg Vortec I have messed with. Anything under 10° is just not enough timing in my opinion.