Pinging and can't find out why

[EyesofThunder]

My 00 PAU is having a fair amount of KR, running 93 octane only (GM designs for 91), and I still get a fair amount that I can't seem to tune out, and even teh STONE STOCK tune has upwards 9 degrees KR, I don't think it did when I got it a few months ago. I have tried and tried, so I am thinking there must be something else at work. It is almost ALWAYS at the moment I enter PE mode.

I have replaced plug wires and 2 of the 3 coils when I got it.
I have gutted air box.
I have tried 160 stat, no help, went back to 195.
I am seeing it with intake air around 60F, so not hot out there, when hotter out, still seeing it around the same.
I have varied stations I get fuel from, typically I have a Shell I go to. But Mobil, Road Ranger, Walmart and Citgo (I typically avoid) still have the same problem, even in different regions.
I have used 10% ethanol and non, no change.
I have bumped up the VE tables too so that the transition time sees more fuel, no help.

Are we even getting 93 octane anymore? How do you check? I am ready to get me 5 gallons of race gas to try.

I am ready to go to E85 again and see what it does. I ran it before and I did see some KR, but not as much, but I want to see if now on stock tune if KR will go away with the current tune (stock) and conditions.

I did turn off EGR and it seemed a little better, (5 degrees instead of 9-10 KR) but that isn't the answer.

It is always in the same region. cyl air 500 mg/cyl to 600. And 2400-3800 rpm seem to be the most touchy range. Dropping timing below stock, no help. Adding fuel doesn't help either. Changing the point we enter PE mode seems vary it a small amount, but again, not the answer.

Thoughts? What is common on the 3800 SC that might cause pinging? Engine is 87K miles, 11K in the last 90 days, so it sees fair amount of miles. Plugs are stock, so I was planning on swapping them out to some NGK TR5's to see if that will help. 87K on stock platinums bad idea? The friend of mine who races a lo 10 sec Small Block Olds 67 Cutlass says to ditch platinums without question.

Edit: I attached a short datalog. I cannot get the Knock Counts PID to read at all. Not once. Does it even work? EFILive and MXScan both can't read it.

 

[Torque Overhaul]

Your long term fuel trims are showing lean, which could be one sign, also in stock forum most 3800S/C vehicles come with 2-7*.
Is there any kind of restriction in the exhuast similar to the GTP's? Where there is a u-bend in the piping where the rear O2 sensor is at? Also another thing to check is to see if your sway bar is hitting in the dp. Some even in stock form have had to flip them. Another thing to check out is the resonator. There was someone who did some testing a few months back and come to find out the mysterious KR ended up being the resonator.

 

[EyesofThunder]

Nope, the C/H bodies don't have the u-bend, glad of that. What is the dp? Not sure on that one. I will look at it.

I am running E85 this week, and doing some tuning with it and KR is reduced, not eliminated, but reduced, but I am running a bit more timing, but there is still a few cells that are actually as low as the stock table, and that is with E85.

I really really would be prefering to see the KS voltage and the Knock Counts, but neither I can. KC isn't working (always 0) and KSV is not available.

Something physically hitting during a resonance might be just it. Nothing is audible, but something could be doing it.

Your long term fuel trims are showing lean, which could be one sign, also in stock forum most 3800S/C vehicles come with 2-7*.
Is there any kind of restriction in the exhuast similar to the GTP's? Where there is a u-bend in the piping where the rear O2 sensor is at? Also another thing to check is to see if your sway bar is hitting in the dp. Some even in stock form have had to flip them. Another thing to check out is the resonator. There was someone who did some testing a few months back and come to find out the mysterious KR ended up being the resonator.

 

[TLIMITED]

My 00 PAU is having a fair amount of KR, running 93 octane only (GM designs for 91), and I still get a fair amount that I can't seem to tune out, and even teh STONE STOCK tune has upwards 9 degrees KR, I don't think it did when I got it a few months ago. I have tried and tried, so I am thinking there must be something else at work. It is almost ALWAYS at the moment I enter PE mode.

I have replaced plug wires and 2 of the 3 coils when I got it.
I have gutted air box.
I have tried 160 stat, no help, went back to 195.
I am seeing it with intake air around 60F, so not hot out there, when hotter out, still seeing it around the same.
I have varied stations I get fuel from, typically I have a Shell I go to. But Mobil, Road Ranger, Walmart and Citgo (I typically avoid) still have the same problem, even in different regions.
I have used 10% ethanol and non, no change.
I have bumped up the VE tables too so that the transition time sees more fuel, no help.

Are we even getting 93 octane anymore? How do you check? I am ready to get me 5 gallons of race gas to try.

I am ready to go to E85 again and see what it does. I ran it before and I did see some KR, but not as much, but I want to see if now on stock tune if KR will go away with the current tune (stock) and conditions.

I did turn off EGR and it seemed a little better, (5 degrees instead of 9-10 KR) but that isn't the answer.

It is always in the same region. cyl air 500 mg/cyl to 600. And 2400-3800 rpm seem to be the most touchy range. Dropping timing below stock, no help. Adding fuel doesn't help either. Changing the point we enter PE mode seems vary it a small amount, but again, not the answer.

Thoughts? What is common on the 3800 SC that might cause pinging? Engine is 87K miles, 11K in the last 90 days, so it sees fair amount of miles. Plugs are stock, so I was planning on swapping them out to some NGK TR5's to see if that will help. 87K on stock platinums bad idea? The friend of mine who races a lo 10 sec Small Block Olds 67 Cutlass says to ditch platinums without question.

Edit: I attached a short datalog. I cannot get the Knock Counts PID to read at all. Not once. Does it even work? EFILive and MXScan both can't read it.

Had the same problem on a 04 GTP,started with a light ping and got worse over a weeks time and then the fuel pump quit all of a sudden.Replaced fuel pump and cured all of the pinging!!!!

 

[EyesofThunder]

I hope not! I'll toss a gauge on and see what happens.

What is fuel press on the L67?

The Datalogs aren't showing whacked out LTFT's, which is what I would expect.

Had the same problem on a 04 GTP,started with a light ping and got worse over a weeks time and then the fuel pump quit all of a sudden.Replaced fuel pump and cured all of the pinging!!!!

 

[murphinator]

you didnt mention fuel filter in your maintenance items , ac delco is preferred in the l67 community , a lot of parts store brand filters limit flow too much and cause lean conditions

 

[Torque Overhaul]

Nope, the C/H bodies don't have the u-bend, glad of that. What is the dp? Not sure on that one. I will look at it.

dp = Downpipe

 

[EyesofThunder]

I bought the car used, 76K on it, the maint records indicated it was done, (markings on the car), but I haven't looked at the brand, IIRC it was silver (like that helps...)....

you didnt mention fuel filter in your maintenance items , ac delco is preferred in the l67 community , a lot of parts store brand filters limit flow too much and cause lean conditions

 

[chris mccord]

My first GTP had a 3.4 set up..for a while.. and had KR issues. I ditched the stock plugs for Autolite 103's and the KR was all but gone. Those are pretty cold for a stock set up but 104's would probably fix you up.

 

[EyesofThunder]

I just picked up a set of TR6's last night, will try them over the TR5's gapped @ 0.050" now.

What is recommended gap? I tend to lean towards a tad narrower than stock. I read an Welcome to article! Search Results Powered by OXiDE search ....radical results (TM)that I found yesterday and it seems to think I don't need colder, but I can't seem to get away from the idea that I should have colder.

In all honesty running too cold on a modern EFI engine, do you REALLY get plug deposits like we used to on carbonators?

My first GTP had a 3.4 set up..for a while.. and had KR issues. I ditched the stock plugs for Autolite 103's and the KR was all but gone. Those are pretty cold for a stock set up but 104's would probably fix you up.

 

[chris mccord]

I ran the 103's with the 3.4 pulley at .050. and drooped KR to almost 0. I don't know how much colder 104's are than stock but they should work. I run 103's now but I tighten the gap between .045 and .035 depending on how much boost I'm running. I'm running between 10 to 13 psi between the different pulleys I use. I assume the KR you are seeing is at WOT.

 

[EyesofThunder]

Just tossed in my TR6's I picked up last night, startup was fine. I haven't driven yet, but seems to do just fine so far....

So I'll take it out later today and play. I still have 1/2 tank E85, so I will toss in the rest 87 octane and then bring timing back to where it should be and go from there.....

Most KR is near WOT, not 100% of it. Attached is my histo of where the knock is. I am NOT showing knock retard from 2 degrees and lower.

I still can't get Knock Counts to work and I don't have a PID for Knock Sensor Voltage which I would very much rather have.

Important things I think to note:

1. Knock most often occurs right @ 125 kPA or higher when in PE Mode. This corresponds to when GM turns on the fuel pump to high speed mode. Do I have a lag there? My next time out if the cooler plugs is to see if that is something. I tried once before, but I think the LTFT learned it out, so I will bring in PE mode sooner and then see if that helps.
2. Most often knock (larger knock) shows up EXACTLY at the point PE mode comes in, and that very often correlates to when the high speed pump kicks in. Correlation? Meaningful? I have moved PE mode in to 37% throttle, no real improvement except I still got knock, but not at the exact same point PE mode kicked in and not quite as much, but honestly with KR it is hard to tell.
3. Was running stock NGK GM installed plugs, and TR5's (stock #2238) with a 0.050" gap, no change. But I rarely see knock in the first 10 min of engine operation from cold start, very very rare. But after that, it is easy to get if I get into it any at all, as you can see, even from lower rpms, but higher cyl/air.

I ran the 103's with the 3.4 pulley at .050. and drooped KR to almost 0. I don't know how much colder 104's are than stock but they should work. I run 103's now but I tighten the gap between .045 and .035 depending on how much boost I'm running. I'm running between 10 to 13 psi between the different pulleys I use. I assume the KR you are seeing is at WOT.

 

[EyesofThunder]

I just drove it, had 50% tank of E85, so I topped off with the rest 87 octane, so that puts me right at 96 octane.

STILL have some KR. Even timing is within 1 degree of stock.

I am ready to go OL and see if this is a AFR issue. If my O2's are weak or off (I will verify them with my datalog to see if they "think" they are good) and base fueling is lean and that is causing my problems.

GRRRRRR

 

[EyesofThunder]

Did find something tonight, I changed PE mode to not happen till 80% throttle, and it stopped the pinging completely. But if I pushed up to 80%, I got KR.

So the problem seems like PE mode isn't working despite what the PCM thinks.

Ideas?