Injuneer

The advance you see on the scanner is the desired spark advance MINUS knock retard. That explains the advance jumping all over the place. The PCM subtracts the knock retard immediately, and then slowly reduces the knock retard, so the advance remains low briefly, even while the knock retard has returned to 0.

The number you see for spark advance is a value from a table in the PCM. It is when the PCM is telling the spark to fire. The table in the PCM has two axes. The horizontal axis is RPM. The vertical axis is MAP (manifold absolute pressure = a measure of engine load). If you open the file in the post post linked below, and scroll down to page 22, you will see a version of the table. There is a separate table for idle/closed throttle (the example is not it) and two others for engine operating under load. There are also "offsets" that are added or subtracted from the main table, for things like (I believe) inlet air temperature.

https://www.camaroz28.com/forums/com...-guide-886891/

But your issue is the crazy and erratic amount of knock retard at idle.

Injuneer

My guess would be this is a mechanical problem. Something is causing erratic noise that the knock sensor is picking up.. Check the passenger side motor mount. if it's loose or the rubber is rotted, a rough idle could cause impact noise that the knock sensor (right next to the motor mount) is picking up.

rlf07

idling is also making a quarter-wots video. engine mounth will be renewed soon. also, I have a vibratory clutch system that may cause problems: (. when I look carefully at the firing numbers. if I press the accelerator quarter and slow, there is no problem with the ignition numbers (I see a low 50 kpa) , if I press the accelerator quarter, but fast (I see a high 100 KPA), my ignition drops to zero . Why a quarter of the gas a hard pressure is 100kpa, I think it's strange to throw 100kpa with so few moves to the accelerator pedal. Note: idle kPa 32, IAC 25, idle speed 800 rpm.

Injuneer

The throttle blades create pressure drop, which creates manifold vacuum (MAP minus BAROMETER = vacuum). Open the blades slowly and flow can increase at a similar rate, keeping the manifold vacuum high (MAP relatively low). Open the blades rapidly and flow can’t increase as quickly, producing little pressure drop, and allowing MAP to BRIEFLY approach barometric (atmospheric) pressure. As soon as flow can catch up with the increased throttle opening, MAP will drop.

The problem with the clutch could be affecting the knock sensor. Very likely it's a mechanical problem and not a sensor problem. I proposed this to a person I consider to be the best LT1 tuner, and he came to the same conclusion.

rlf07

I get it, it makes sense. so, is there a difference between the fact that the absorbed air is cold or hot when it comes to slowing the rapid output of map high kpa? also my tb elbow ebay silicone model (ebay Cai complete) the silicone compartment at the tb entrance stands wrinkled and trapezoidal. WOT and high kpa may cause incompatible behavior, does it cause air flow problems? in short, what should be the moves that prevent map from rising quickly ?

Injuneer

Has nothing to do with air temperature. When you open the blades fully, the intake manifold is exposed to atmospheric pressure (~100kPa). It reaches that pressure until air flow increases and causes a pressure loss across the blades.

MAP rising rapidly when the throttle blades are open rapidly is a natural phenomenon. It is not a problem. Your problem is knock retard.at closed throttle idle (at least that is what you told us the video was for), the table of spark advance at closed throttle is dependent on RPM only.

Injuneer

And I still think you need to start a NEW thread, describing YOUR SPECIFIC PROBLEM in detail. Is it EXACTLY like the post you quoted? If you have a stumble at 2,000 RPM, it could be due to a faulty inlet duct, after the MAF sensor. It just isn't clear to me what problem you are trying to solve.

Was the video of the scanner strictly at closed throttle idle, or were you suddenly opening the throttle? There is no way to tell that from the video.

If you feel there is a problem doing this due to language barrier, I will help you make any required corrections.

rlf07

in the video, idling attempts small and sequential wots. I'll try to solve problems from what you write. I'm waiting for the parts that need to be replaced to come from the cargo..in this table, when I make sequential Wots at idling , the ignition drops down to cons. sometimes it stays zero.

SerdarD

@Injuneer Hello There. I'm friend of @rlf07 helping him with the tune to solve the problems on his car, all mechanical works done by someone else I ll try to clarify the former explanations. Former owner was spraying NOS with 30 lb/hr injectors and PCM was tuned to run SD with ridiculos timing tables. And many other stupid changes. I m still wondering how it wasnt broken. lol

Current situation NOS system taken out, The car is 97 TA M6 with stock bottom end with few minor bolt ons such as Edelbrock shorty headers, CAI, Borla Exhaust. 24 lbs/hr ACCEL BlackTops, all emissions deleted ( excl EVAP.) Catalytic converters deleted and 2nd O2 sensors cancelled. I have loaded stock tune which i get from well known 97 stock A4 car and made all necassery changes according to shorty headers, exhaust, o2s, injectors, deleted emissions, trans related changes, VSS correction etc. etc. Running with MAF mode. I have used JET DST and we dont have a chance to get a datalog but have an obd2 scanner with limited abilities while engine is running.

You were asked about the video of the scanner . The answer is he was suddenly opening the throttle while car is stationary. Knock retard and/or stumble is happening between from idle to 2000-2500 rpm even stationary or while driving but just with sudden throttle. If he press the pedal slowly there is no stumble nor hesitation.

I m 100% sure with the tune and the problem is related to mechanical issue like you mentioned above,

I appreciate if you ( or anybody) can provide bone stock tune for 97 TA M6 than i can compare it once again.

Best Regards.

Injuneer

I'm not a "tuner" and I do not have any stock files. They are out there on the internet. I don't know exact sources, because I don't even use the stock PCM on my setup. I do have a copy of what is supposed to be the stock timing table for an LT1. I'll try and attach it below.

Part of the confusion here is the reference to the very first post in this thread, and saying he had the exact same problem. If I read your post correctly, the problem is STUMBLE AT LOWER RPM WITH RAPID THROTTLE APPLICATION, AND KNOCK RETARD. The person who started this thread claims the timing was dropping to "0" and THERE WAS NO KNOCK RETARD.

I encouraged him several times to start a new thread to avoid confusion, but he didn't do it. I know he has a language barrier, but remember that affects both parties in a conversation.

Could this be as simple as a hole, or a tear, in the rubber elbow between the MAF sensor and the throttle body? Could the lower edge of the elbow be folded over and not attached to the throttle body? These are common problems, and can cause the stumble because the PCM doesn't add sufficient fuel to match the air bypassing the MAF sensor = lean A/F ratio = knock retard.

SerdarD

Thank you for your response and shared timing table.

I totally agree with you about saying he has exact same problem under different threads with related to different symtomps. It creates confusion and affect all parties looking for solution. I m pretty sure because of language barrier as you say. I ll call him to explain this situation in native language to not happen again also the suggestions you referred.

Best Regards