FAQ: What is spark knock? What is KR (knock retard)?

Larry is correct about the load. One of the things I did to my PCM's shift program is have TCC release almost instantly upon application of throttle. This minimizes the extra load, reducing KR. Another thing is I increased my upshift RPM points, even with light pedal application. This puts you into higher RPM when you reach the next gear, which also lessons load to the engine. Last thing is programming downshifts to come earlier, so when you are in a high load/low RPM situation, downshifts happen more easily, again resulting in higher RPM (less load to the engine). In short, the engine resists the temptation to hold on to each gear as long as possible.

You would think this results in worse MPG, and it does if you don't drive economy in mind. But if you do, your MPG can be just as high as with the stock tune, minus the KR from high load situations. An additional benefit: the engine is much more responsive in every kind of driving.

Why didn't GM do it this way from the factory? At least two reasons: 1) It's a Buick, and high RPM doesn't feel soft and fluffy, 2) It forces the driver to attain higher MPG, so better consumer satisfaction for those who don't know how to drive economically.

at what coolant temp does the sensor start to record knock?

158ºF and above, unless you reprogram the PCM for a lower temperature (-40ºF)

Ok I have 0.0 KR when I hit high rpms it shows .3 to 3.0 at times depending on the gear is this a good or bad thing?

Johnny5 wrote:

Ok I have 0.0 KR when I hit high rpms it shows .3 to 3.0 at times depending on the gear is this a good or bad thing?

Not sure what you mean? KR is never a good thing. If the KR is not RPM related it could be false knock. When do you see this KR? It is normal to get a few degrees under WOT when the car is warm.

th3fr4nchi5e wrote:

Johnny5 wrote:

Ok I have 0.0 KR when I hit high rpms it shows .3 to 3.0 at times depending on the gear is this a good or bad thing?

Not sure what you mean? KR is never a good thing. If the KR is not RPM related it could be false knock. When do you see this KR? It is normal to get a few degrees under WOT when the car is warm.

I just got my scan gauge in monday and im trying to learn it.. So its says 0 KR but when im on the gas right before it goes in to the next gear on the throttle it spikes but other than that no kr my ignition advance is at -22 long term fuel is stationed at 16.9

Please don't freak out the new guy about KR. Johnny, your car is running normal, period. A bone stock Riviera WILL see sometimes 10* of KR on super hot days in 3rd gear or cruising uphill in 4th.
It's not going to explode, it's not going to die. It's normal.

3º of KR is within normal range (although not optimum), but 16.9 LTFT is definately not good for fuel trim. Sure a bone stock Riv may see 10º KR under load, but this is far from normal. Something isn't 100% for that to be happening. If you allow a car to run in 8-12º KR territory for enough time, pistons will frag.

Johnny5, your KR isn't too bad right now, but we should figure out why your LTFT is pegged at +16.9. Actually, I thought the max was +16.4, so that's a bit weird.

AND, the SES light would be on setting a Lean code if it really were pegged at 16%.....

Here's one for you....
Since we got the 104 plugs installed last weekend, my KR has virtually disappeared. BUT when it does arrive in temporary spikes, it spikes higher than ever before now.

Previously I would see momentary spikes of 9-10 degrees. Now I am seeing spikes up to 14!

The only thing changed were plugs. Overall, it's been a surprisingly awesome improvement for KR control. But these crazy spikes ive never seen before kinda scare me.

I am still not comfortable with driving it like I stole it without scanning the whole time.

Once I had a Mini AFC installed inline with my MAFF sensor. At some point the AFC stopped functioning and caused my LTFT to max at +16.4. The engine would hardly run when at idle, would buck while cruising at low RPM. But it never threw a DTC, or any code for that matter. I know it should have, but never saw the SES lamp.

charlieRobinson wrote:

Since we got the 104 plugs installed last weekend, my KR has virtually disappeared. BUT when it does arrive in temporary spikes, it spikes higher than ever before now.

Previously I would see momentary spikes of 9-10 degrees. Now I am seeing spikes up to 14!

There are other variables that are not constrained: fuel, barometer, ambient temp, engine loads. As these variables change from trip to trip, you'll get different levels of KR.

You're playing with fire running the 3.4" without a tune and breathing mods. I've never seen 14º KR, even with 3.2" pulley. 15º-ish is the max value, so basically your engine is "knocking" on the door to firey death. As winter comes, the air will be more dense, and you could see more. Be careful, charlieRobinson!

AA wrote:

Once I had a Mini AFC installed inline with my MAFF sensor. At some point the AFC stopped functioning and caused my LTFT to max at +16.4. The engine would hardly run when at idle, would buck while cruising at low RPM. But it never threw a DTC, or any code for that matter. I know it should have, but never saw the SES lamp.

  I reflashed my MAF tables 3 weeks ago back to stock LQ4. Lean code 2 days later.
Cars are stupid.....

Charlie....14* wtf? All we did was put 104's in it. That makes no sense whatsoever.

Quote :

Charlie....14* wtf? All we did was put 104's in it. That makes no sense whatsoever.

He squeezed in a 3.4" pulley when you weren't looking.

I was running the 3.4 with 605 plugs and had minor KR with smaller spikes

Now, with the 104s I see 0 KR but when it spikes it spikes harder than before with the 605s.

Thats the conundrum.

I've told you before that I was never able to run my 3.4 safely until I had at least the 1.9 rockers installed. I don't know why you think your car is any different.

Also, maybe you have a spark plug wire leaning on something that's only getting touched under full throttle? Do your wires have sleeves over the contact/rub points?

Ah. He did have a wire that was touching the rear O2 when I installed the rear plugs. I re-routed it away from the 02. But, it was turning white. Maybe the insulation is shit and grounding on the lift bracket now?

The 3.4" was on it when he came over. We scanned and logged. NEVER even saw 9* let alone 14*. This was all before we realized that we (apparently) can't tune a '99.

I have 0 KR @ WOT with ~10psi

No problems.

But sometimes, out of no where, I will see a spike thats 8-14 (14 was just the highest I've seen)

It lasts for less than a second then drops back to 0.

I know the knock sensors are microphones so could it be something thats NOT detonation?

That is suspicious. When does the spike occur, and how long does it last? If it's false KR, could be something metal making contact with the engine when you shift. You have to experiment, log, and graph against other parameters to figure out false KR. It's rare.

Shift points are also where real KR generally forms. You go from high RPM to high load near instantly, so KR spikes in that area are pretty common.

Assuming it's real, there are the variables I mentioned. If you change nothing else right now and put those 605s back in, you'll still see 14º, maybe more. You can't expect the car to run exactly the same every time, because of the variable out of your control. That's why we tune for 0º KR, so your worst case scenario will be 3º.

Example: my engine is tuned for 0º KR. At WOT on the 2-3 shift, going uphill, I might see .3º some days. Other days, I see 1.5º on level road. One day I was seeing 3º quite a bit and was like WTF, so being near the end of my tank I filled up at a different station and it went back to zero KR.

At one point out of curiosity I had a fuel pressure gauge attached to the fuel rail and ran it under the edge of the hood and taped it down above a windshield wiper. It was very interesting to watch the FP while I was driving. It may be worth doing something like that to see if you have a FP drop when you see the KR spikes. Logging would also show a lean spike if that were the issue.

Do you have anything to log multiple parameters with?

Question Charlie....was your Traction Control ON when you saw this spike?

If it was, turn it OFF and see if it still spikes. Just a shot....

deekster_caddy wrote:

At one point out of curiosity I had a fuel pressure gauge attached to the fuel rail and ran it under the edge of the hood and taped it down above a windshield wiper. It was very interesting to watch the FP while I was driving. It may be worth doing something like that to see if you have a FP drop when you see the KR spikes. Logging would also show a lean spike if that were the issue.

Do you have anything to log multiple parameters with?

I do and I will.

Abaddon wrote:

Question Charlie....was your Traction Control ON when you saw this spike?

If it was, turn it OFF and see if it still spikes. Just a shot....

Yes. I will experiment with it off.

This is all relatively new, so I will need some more time to experiment to get a better idea of whats going on.

Abaddon wrote:

AND, the SES light would be on setting a Lean code if it really were pegged at 16%.....

It is illuminating at night very ugly ses Po441 it will not go off either I looked on YouTube for a relief sign but nones given its running lean you can smell it

Johnny, the link below is directly related to P0441.

https://rivperformance.editboard.com/t7197-p0441-1441-evap-emission-canister-purge-keeps-coming-back

It's certainly possible that the affect of your P0441 concern just might be why your car is running lean. You may have a vacuum leak in the EVAP system, or something is wrong with the Purge system. Either of the 2 problems can cause the engine to run lean. Read that thread....

Abaddon wrote:

Johnny, the link below is directly related to P0441.

https://rivperformance.editboard.com/t7197-p0441-1441-evap-emission-canister-purge-keeps-coming-back

It's certainly possible that the affect of your P0441 concern just might be why your car is running lean. You may have a vacuum leak in the EVAP system, or something is wrong with the Purge system. Either of the 2 problems can cause the engine to run lean. Read that thread....

I seafoamed it one day and no white smoke came out so driving it after 4 days coming home the car started to sputter at the stop sign all my lights came on and I put it in neutral to keep it from killing.... so got it on my street punched it a bit and it back fired huge clouds oof white smoke filled the streets and I parked and let for about 5 minutes till the smoke cleared cut it off and back on ses was on ever since

You guys with tuners.. are you able to change the KR noise floor variable in your tunes?

I am reading http://www.zzperformance.com/blog/kr-graph3-what-the-pcm-believes-to-be-real-knock/

the article about KR at ZZP and they say that the knock sensor/microphones can really pick up engine/trans noise and misinterpret it as real KR.

The solution this guy had was to change his KR noise floor so that the false KR would be too low to register.

So, can you guys confirm this is doable with HP tuners and the like?

Thank you!

ZZP wrote:

So What’s The Bottom line: why do I want to change the KR noise floor?
The point to all of this really is to show where the knock voltage is at idle, which in my car is at about 1V Peak. Prior to DHP changing my noise floor, I was getting HEAVY KR by just accelerating away from a stop normally. It was terrible. Every time I accelerated: even lightly, I got substantial KR (10-15 degrees). I never had it that bad until right after my trans was rebuilt. Since then it has been very bad. DHP asked me what my noise floor was on the knock sensors, and from my scope shots, I was able to tell him approximately 1 volt. Dave then raised the stock setting of 0.5 volts up to 1.0 volts. Since then, I have to REALLY work at getting KR. I have learned since then exactly what I have to do to get this kind of KR to occur. Thankfully, this fix in the PCM has prevented me from seeing KR under normal driving, spirited driving and racing.