V8Astro Captain

iTrader: (1)

In WinBin there is a value that says EGR off %TPS threshold. If I set this to 0, the ECM will then leave the EGR off(?). So no change in throttle turns the EGR off right?

Right now it's set to 50, so 50% change in throttle turn the EGR off.

What do you think?

EDIT: I read an archived post a while ago and found some stuff on this. I just looked and couln't find it again. It was something about the EGR temp enable being inverted(?). So 01 in hex means it turns the EGR on at some rediculously high temp, correct?

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'92 Astro, GM crate 350, Holley Pro-Jection Intake, MSD 6AL, 3.42's, 2.5" exhaust, Flowmaster 40 2 chamber, B&M 2nd stage shift kit, 255 60 R15 tires on AR-727's, Polished & Bored TBI, Custom EPROM in progress

[This message has been edited by V8Astro Captain (edited November 14, 2001).]

JPrevost

I think this is an old issue that was figured out a while back. I believe if you do a search for 747 egr on temp there will be a listing as to what you should edit. From what somebody said, the EGR still goes on even if the ecm doesn't know the speed! Makes me wonder what the on/off speed does. I think there must be some sort of order to the priority of having EGR on or off, temp being the number one.

fast_broker

iTrader: (1)

Yep, the EGR will still go on with no VSS. Must be forced for emmisions reasons. Edit the TEMP to "0", which is actually like 255 degrees to the ECU... Not sure of the address, though.

V8Astro Captain

iTrader: (1)

Yes. In my PROM there are Hi/Low VSS variables, but they are both blank. So I'm guessing mine doesn't care what the VSS is. Looks like its just temp, MAP, and TPS.

The address is 1B3.

[This message has been edited by V8Astro Captain (edited November 15, 2001).]

fast_broker

iTrader: (1)

Thx, Astro.

Did you get your BLM's straightened out, Astro???

V8Astro Captain

iTrader: (1)

Not quite. I'm working on it tho. I just changed my intake which turned out to be big sh!tty mess. JoBy just put out a new version of WinALDL with some mods I recommended so I'm looking forward to gettting back to tuning.

Grumpy

Never ask me what I thik, unless you want the rants that go with it <G>..

Anyway, turning off the valve is only part of it, there are depending on the calibration your running timing, and fuel corrections that run with the EGR apply.

So the proper way is setting the temp to some ridicuous high enable temp, and then switching off the diagnostic flag.

Be sure to hunt around for the 42 code patchs

V8Astro Captain

iTrader: (1)

Code 42 patches? What are these?

JPrevost

yeah, what are these?

Grim Reaper

I completely agree with Bruce. The calibration makes a lot of adjustments to the mixture depending if your EGR is functioning or not.

The most effective way to positively stop the EGR from functioning is exactly as Bruce suggests - increase the EGR Enable Temp to a ridiculously high number. Other methods can result in the ECM thinking the EGR is still functioning under certain circumstances and it will throw the calibration off if the EGR is in fact disabled or missing.

[This message has been edited by Glenn91L98GTA (edited November 26, 2001).]

JPrevost

Still can't find any information on the "code 42 patchs"
If all you're talking about is changing the EGR on temp to a high value. Isn't the value backwards, high temp actually is infact low temp. So you want to set the value to the lowest temp.
Anyways, I'm still getting a code 42 error after driving a lot and I have no f'ing idea what to do now. I'm 2 winks from scrapping the TBI and going to carb.
Why can't the ecm data stream show the actual advance on the distrib? Why does it have to be stupid and show me crap like "learn control is on" "closed loop" If the BLM is moving no **** the car is in learning and in closed loop. Shakes head. I will never fully understand.

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, Jon (350 TBI!)
91 Red My website

fast_broker

iTrader: (1)

Yes, JP, "00" is as "high" a temp as you can get. That translates into 255 degrees F, I think???

JPrevost

In tunercat it's backwards. 00 is actual negative 40, not 255. oh well, I remember Grumpy pointing that out to me before

Grim Reaper

Yes, hex 00 is -40*C (-40*F) and hex FF is 151+*C (304*F).

Ken73

Jon, after some digging, I found that (error) code 42 is something to do with EST problems. From what I understand (anyone feel free to correct me) the ECM goes through a "knock test" - it actually forces the engine to a high advance to purposely see if the knock sensor is working. (It forces the engine to knock.) If it doesn't, then it trips the code.

I believe the amount of advance to trip the sensor can actually be set - but if you have a bad sensor, OR if you're running too rich, you may trip the code.

The "code 42 patches" that Grumpy is (possibly?) referring to are part of the "Hiway747.zip" file on the GMECM site. It's the "esc_done" patch - it trips the bit that makes the ECM think that the test has *already been performed* and passed - and therefore can't trip the code. I would first talk to the GMECM guys and see if this patch can be applied to the '8746 ECM before you try it though. I believe it's primarily for the '7747.

I may (very well!) be wrong, but this is what I've read into it. Grumpy?

Ken

Ken73

After reading the '7747 (I can only assume the '8746 is similar) hack, I see where you can disable the code 42 from happening at all. Just like the other error codes - they can all be disabled, literally.

Ken

fast_broker

iTrader: (1)

"00" in the actual 7747 BIN/code is a high temp, right?

Ken73

I have no idea - I just grabbed the TunerCat TDF editor and made that entry in TunerCat. I'm working on a TDF and calibration help file that fills in some of the blanks we've been drawing (like this.)

Ken

fast_broker

iTrader: (1)

I wish TunerCat would include it in their "free" TDF $42 editor... That way, we wouldn't have to figure it out. Eliminating EGR has GOT TO BE ONE OF THE MOST COMMON things done with custom PROMs, right?

[This message has been edited by fast_broker (edited November 30, 2001).]

JPrevost

Ken, please explain the hack. I'm pretty sure my knock sensor is working, I just don't have EGR. Could the problem be that I'm still using the 305 ESC with a 350 knock sensor? The self test makes perfect sence but why would my car run like crap when the SES light turns off, assuming that is the end of the test.
I'm really pissed off about this. Should I replace my ESC? It's obviously working to control the advance of the dissy but I guess it doesn't like the knock sensor. Please help me out guys, the car basically shuts down and scares the crap out of me on the highway. I have EGR disabled and the timing seems to be pretty good.
Any help would be great.

fast_broker

iTrader: (1)

Maybe you don't actually have the EGR disabled on the ECU??? Run a voltmeter to the EGR solenoid wire(s) and check to see if the ECU ever tries to activate it. If the voltmeter shows voltage or voltage changes, it's a sure bet the ECU is in EGR mode trying to active the EGR valve, adding tons of spark, removing fuel and also checking for EGR function with the internal EGR "test". If the EGR test function is "ON" and you get an EGR error (ie fail the MAP change test) , the ECU will still run EGR fuel AND spark parameters, I believe. ie, you will see voltmeter changes at the EGR solenoid wires. This check worked VERY WELL for me.

EDIT: Just realized you got a 42. Doesn't that mean you have distributor module/pickup coil problems (EST), not ESC (knock control?) problems??? ie, the ECU doesn't have proper rpm data and/or cannot control the engine spark and the module reverts to non-adjusted spark (feels like NO POWER because you are running only your initial advance ALL THE TIME!!!) or just shuts off and makes no spark?


[This message has been edited by fast_broker (edited November 30, 2001).]

[This message has been edited by fast_broker (edited November 30, 2001).]

Ken73

Jon, I'm only going to fathom a GUESS at this point. I try really hard to read up on this stuff and understand it so I can help not only myself, but others as well.

My GUESS is that when you trip a code 42, it either bypasses EST, *or* it goes into limp mode, hence your engine almost "shutting down" as you say. (What are the actual engine running conditions when it acts up? Does it just not have any acceleration?) Basically what fast_broker describes. Still, I would think the SES light would STAY ON if that happened.

The "esc_done" hack that I'm talking about is for the '7747 - it tells the ECM that the knock test has already been done (even though it hasn't) so it can go into Highway (Lean Cruise) mode. This way, it never actually forces the knock or even goes through the test. I don't know how to go about it in the '8746 though.

What have you changed in the chip for this to happen, anyway??? Can you revert to an older version of a chip and start fresh? That's the best thing to do when you get stumped. A piece of advice I got from Grumpy - make changes but TAKE NOTES OF WHAT YOU DO. It'll help you figure out where you might have gone wrong!

Ken

JPrevost

FB, my EGR isn't going on. If it was I would have an SES light and an error code after it tried to do the vacuum test!
SO, my EGR isn't going on or off, BUT when I drive for a long time at about 2800 the car will just quit on a random time. If I turn the car off and start it back up it doesn't come on until after I've been cruising at a steady speed (steady foot = steady TPS sensor voltage). So with that said I think I've narrowed it down the that damn spark knock test. My problem is that I don't have the highway mode enabled so what the **** is the ecm doing when it checks the knock sensor.
Ken, I take notes on all my burns.
Can somebody tell me why the ecm has to do this knock sensor test.
Even with my clogged cat converter I didn't get any worse gas milage!! The car was hating me the whole way back to school on the 540 mile drive. It just worries me that after I drive for some amount of time, it does the "engine shut off" thing and the pedal doesn't help.
Sometimes the SES light would flicker on and off REALLY fast, then it would either stay on or go off. When it would flicker the car was basically off. The KEY hint to my problem is exactly this: SES light comes on and nothing happens. When the SES light goes off the car stumbles. So when the SES light flickers the car just about dies and I almost die from getting rear ended by an 18 wheeler before I have time to put the car in Neutral and pull over. I haven't had to pull over YET. It's caught itself at about 2000rpm and the SES light becomes constant on or off, doesn't matter, no difference in performance or gas milage.
Remember, I do have a clogged cat converter from running too rich and having a bad tran mount for too long. My BLM when cruising at that MAP and 2800rpm was dead on 128.
All I need to know is what could cause this screwy behavior. Is it eprom related (highway mode), is it ESC related, is it a loose wire grounding somewhere, or what?
Thanks guys for all the help. I'm going to look into the 42 patch when I get done with finals and bach home.

fast_broker

iTrader: (1)

What if your ECU thinks it PASSED the EGR test? It happens on modified engines and it happened to me!!!!!! Or, if you have no VSS, you'll never get to the "test" and the EGR will still eventually activate.

Try my idea, please. The fact that there is no EGR light/code could mean that the ECU did pass the test, right? Don't rule it out until you verify EGR is not active. My method is the only way to be sure, as far as I know. I beg you to try it. Takes about a minute or five to do... Do you have added EGR spark and reduced fuel in your BIN????? If so, try a BIN without the added spark and see if you notice a knock change/power difference...

EDIT: I'll say it again, I think it could be your distributor module and/or the connections/wires leading to it and the other appropriate supporting devices, like the pickup coil. Isn't a code 42 the error you get when you run the car to set the timing with the spark control bypass disconnected??? Ya' with me??? Sounds like you are going from about 35 degrees of spark advance IMMEDIATELY down to your initial setting (of say 0-10deg advance only) while driving on the highway!!! That is NOT GOOD It will feel like the engine has died and will catch itself as rpms drop!!! Be careful. Sounds like an intermittanly bad module/connection!!


[This message has been edited by fast_broker (edited November 30, 2001).]

Ken73

The more I think about it, the more it sounds like a faulty part, rather than an ECM/EPROM/value problem. Sounds like it's doing the spark test, and that triggers whatever part is broken to crap out.

Wow.. imagine that - an error code that actually MEANS something!!!!

It very well could be your ESC module, as you first suspected.

Ken

JPrevost

Ken, I agree, it must be something stupid part. I just gutted the cat and still having problems. This is probably a good time to get that 350 ESC like I was suposed to after the swap! The knock sensor is farely new, as old as the motor which is 6 months.
I just thought about something. If the car is sencing ping from a nasty vibration wouldn't the car run like crap because the ecm would be pulling lots of timing out all the time and at a certain point wouldn't it then caust a closed loop to the point where it would start to set off the knock from too much retarding. I didn't really look too good at the spark amounts but I'm going to go log that first thing tomorrow with both winaldl and diacom.
This is what I think is the problem. Not the actual ESC. If it was the ESC or part of the dissy then I would have some MAJOR issues driving the car and I wouldn't get normal gas milage and I wouldn't have the car running "well", it would just not run if it couldn't control the dissy! This is why I think there is just some nasty constant knocking going on and so it's just retarding like crazy.
Are my symptons of a car that is getting bad knock? It's got nasty hesitation, starts fine for the most part, doesn't like the knock highway test, and it just HATEs WOT.
Grumpy...THIS is why I wish we could have a data stream of how much timing the ecm is running! Is there any circuit that could show me the position of the advance with a multimeter or someplace on the dissy that I could watch the timing?
If not, I think I just thought of a great product for an EE major to work on .
You guys are the best, I don't know what I would do without the help.

------------------
, Jon (350 TBI!)
91 Red My website

V8Astro Captain

iTrader: (1)

The cat was hollowed out on my brothers IROC and it has caused nothing but probelms. The EGR valve, solenoid and lines are new and it still throws a code. I don't think it has enuf backpressure anymore.

Ken73

Location 0066 on the '7747. Jon, you really need to send me the '8746 HAC so I can poke around in it. Place this location in the ALDL transmit section - replace something that you generally don't use (say, battery volts?) with this location and it should show you the actual spark advance (as it's happening!)

Mind you, I don't know what the location for the '8746 is - could be similar? E-mail me the HAC if you would...

Ken

Grumpy

You got it.
Do the patch,
set the enable to 254d, 01
disable the flag.

If your working on a car TBI then you'll need to read thru the code and chase it down. I haven't read thru the whole car code but from the simalarities I would imagine it's in there.

Least that's the way I'd do it.