Knock retard happening without knock sensor? 16197427

[Scorp1us]

When I'm stabbing the throttle, I see knock retard kick in. I have no idea why? Is there some program logic that adds knock retard based on other readings?

[Fast355]

When I'm stabbing the throttle, I see knock retard kick in. I have no idea why? Is there some program logic that adds knock retard based on other readings?

Disable burst knock and see if it goes away.

[Scorp1us]

Cool thanks.

[Scorp1us]

Nope, I still get it.
I tried changing all the parameters that would make sense.

[Scorp1us]

Here is a log.

[sturgillbd]

I just reviewed your log. If you could post your bin, I could tell more about what is going on. I see some AE activity and I believe that is because of your cam. You may have to adjust your map difference to enable AE at idle parameter. I also notice you are in open loop in the log. Do you have your bin set for open loop at idle? I put a slightly larger than stock cam in my build and had to tweak the AE settings. At idle AE was active quite often and it caused my plugs to be fouled because of the extra fuel.
Brian

[Scorp1us]

I have only tuned the spark timing to match the distributor specs of the IH dist. -- EXCEPT idle and 400 RPM to stop a stall.
I have only tuned fuel for best sounding idle. The rest is GM
Idle cells are:
RPM -- MAP
400: - ridiculous advance for saving idle from a stall
600: 45-60 (at start of tuning, it was 60-65, adding fuel brought it down to 45)
800: 45-50
1000: 45-50
1200: 35-40
1600: 30-35

Because I need to run rich with the cam at idle I have open loop idle enabled.

What do I need to change to have AE work properly?
What is the deciding factor for the software to switch from the idle to open throttle VE tableand Main spark open/closed throttle tables?

[sturgillbd]

Your lower vacuum with the bigger cam makes the PCM think the engine is under load and adds fuel. If your engine has a choppy idle, and the vacuum is not steady, AE can be triggered by the fluctuating map signal. When AE is triggered, it adds fuel. The deciding factor on the VE tables are RPM, TPS, MAP etc. Also with the 7427 PCM, it is important to have a VSS connected. The PCM needs to know when the vehicle is moving to prevent stalls when coming to a stop etc. I'm getting ready to look at your bin and will see if I can help you.
Brian

[Scorp1us]

Thanks Brian!

I could never figure out what I needed to connect VSS to the PCM. Accounts vary. Some talk about a vehicle signal buffer. Is that in my computer? A separate external module?


Also, does connecting the brake signal do anything? And if so, how is it connected (+12 when brake on or GND when brake on?)
EDIT: I see. 12v no brake, shorted to ground on brake. But does this to anything programming wise?

[sturgillbd]

I bought a VSS from TPI parts. Same one from JAGS that Run. http://www.jagsthatrun.com/Pages/Spe...eedometer.html Speed Sensor, # 2PRS. I wired it directly to the PCM and set Output speed not from DRAC in bin. One wire goes to either pin F12 or F13 and the other goes to ecm ground. I will have to check my notes to tell you which pin it is for sure. The information is in one of the threads here on GearHead-EFI. The brake signal is mainly used for TCC control on lockup converters. Now back to your AE. I counted 5 times AE was triggered during that log. Your vacuum stays fairly steady. After looking more closely, AE is not your problem. If you want to turn off Burst Knock, set minimum TPS for burst knock retard to 100%. See if your knock retard at idle goes away. Did it take 35 degrees of spark advance to smooth up your idle? Back to my earlier post about AE, I wasn't implying AE causing burst knock. I was thinking it may be contributing to a rough idle. AE at idle was basically flooding my engine slowly. Try the burst knock setting and see if the knock retard goes away.
Brian

[Scorp1us]

Thanks Brian! I'll get on that in the morning.

My idle is spoothest at that. I tweaked fuel and spark to get it that smooth. Now, I could probably cut the timing a bit but it would sound worse. I was basically trying to move the active cell to the left (lower MAP) as much as possible. Those values are what I settled on for using the most leftward values.

One last question... Any idea why my IAC works itself to zero despite stable running?

Oh, I have one of those modules from JTR. So all I need to so is connect it to the right pin and ground? Easy peezy!
F12 - Trans speed - Brown - VSS - Eratic shift
F13 - Vehicle speed - DK blu - VSS - Fuel cutoff

I'm guessing F13?

[sturgillbd]

It will be F13. As for IAC working its way to zero, try turning the throttle stop screw counter-clockwise 1/4 turn.

[brian617]

One last question... Any idea why my IAC works itself to zero despite stable running?

Try turning your throttle stop screw out a 1/4 turn at a time to get IAC control.

[Scorp1us]

It's not going to be confused with my open loop idle?

Why is the IAC moving at all?

I hesitate because I tuned it once. What should happen eventually? It started out ok but kept lowering itself. Should I hot a poiunt where the throttle plate is shut and IAC hovers around 40?

[brian617]

You want somewhere around 15 counts at idle on a hot engine. The more airflow over the blades and less through the IAC hole the better the fuel atomization. It's one of those things that needs attention as your tune gets better and better.