Alright, here goes: This is NOT another "my car runs rough- what should I do?" So please no more of those "clean the IAC" cop-outs! I'm interested in the core tables in a $6E bin that are utilized in tweaking the idle for stability.

On my system, I have to modify the stock bin so much to get appropriate fuel that it gets way rich at idle (warm and cold) and tends to idle high. I've cleaned the IAC, checked the injectors, Triple-checked for vacuum leaks and reset idle speed to no end (per my factory shop manual directions). So assuming there are no mechanical issues, can anyone provide a basic description of the following tables?

1989 -165 $6E def from TunerPro:
* O2 error reduction gain vs airflow - raising/lowering the values here is supposed to do what?

* Integrator Delay vs airflow - increasing this value "numbs" down the O2 sensor and should smooth surging?

* Integrator Delay Multiplier vs Error - no idea here...

* Spark Correction: LV8 vs Coolant - this doesn't seem to affect my total spark advance when compared to the main spark advance table. Any ideas why?


I've tried tinkering with these tables with IAC plugged in and unplugged, open loop or closed loop- and I can't say I've ever discovered anything outside of "hey, it's really easy to stall this SOB out!"

I'm just truely frustrated with the high idling and stalling when going into gear, and I've been tinkering with Tunerpro for a couple of months now to no avail. Can anyone provide some broad strokes on where to go with the idle characteristics (outside of taking a stock bin and starting over AGAIN...).

Shew.

 

Did you make changes to your main spark advance table? What is your commanded idle speed vs. temp? Is your idle smooth, just higher than expected or is it rough as well? Both in Park and in Drive?

 

I think the main problem is that it's rich at idle (from unreliable cold O2 counts and the rich black smoke coming out of the tailpipes when it's cold! ), but basically the symptoms are surging when cold start ( under 100* F), threatening to stall out. When I put it in gear it will stall 100% of the time UNLESS the car is warmed up and in closed loop, then it will just dip down 300 RPMs and survive. It also idles high all the time (even closed loop).

Idle tends to be in the 900-1100 RPM range (commanded idle is 900RPM ). I've kept it high in an effort to prevent stalling and to help troublshoot the tuning... When setting idle and TPS, it will idle pretty well at 600 RPMs (so it isn't impossible or due to the cam). Plugs are recently new and in good shape also.

I'm contemplating a new IAC unit but the existing one is only a few years old and seems to be functioning properly- the ECM counts just don't always represent what I program it to do.

I've tried pulling out fuel, but my Open loop vs LV8 table is essentially bottomed out at idle LV8 values (40-50) and if I lower the Open Loop Fuel vs Coolant, then I'll go lean at WOT. This is with SVO 24# injectors (~2 yrs old).

I figure it has to be me screwing something up in the chip, and I was able to make minor progress on cold idle last night but it's still a very long way from perfect. I'm not entirely ruling out mechanical issues, but at this point I'm not detecting anything like a lifter or injector that could be responisble. Engine runs strong under part and WOT runs with minimal smoke (I keep it fat and happy at WOT) and tends to be fairly reliable under closed loop conditions. I'm just hitting the wall here and looking for some fresh insite.



EDIT I have experimented with the main spark advance tables, but I've found it's most happy at 20* advance. I have tried more advance (speeds up the idle) and less, but can't say that either have helped the stalling issue. I may need to just figure out a way to reduce the fuel at idle and see what that does. O2 readings are in the 915's at idle, and I have a hunch that it would be happier closer to the 700mv's but I cannot seem to get it there through the normal methods.

Worst comes to worse, I'll throw a bone stock BIN back in my emmulator and see what that does. But I WOULD like to learn what all those tables are for before I give up on it.

 

"but basically the symptoms are surging when cold start ( under 100* F), threatening to stall out. When I put it in gear it will stall 100% of the time UNLESS the car is warmed up "

Mine, after the engine rebuild is doing the same. I'm hoping that a new chip for my 1992 accounts for the upgrades from stock (LPE 211 cam and Stage III heads (and matched intake) from PP&C)

 

20 degree's base or is that what is in your spark table at idle RPM's?

What is your total advance at idle?

 

I'm speaking in terms of total advance per the main spark advance table. this is verified by running Datamaster while I make changes to the emmulator/chip. So 20* total advance at idle (frankly, 1200RPM and under), with the appropriate 6* base in the distributor and specified in the ECM.

 

Cant help with the tables but my 87 with mods has 26* advance at idle on datamaster. Just something for reference.

 

I assume 89 is still a MAF car.

Look into MAF table #1 in the idle air flow region (counts < 320 or so). Reduce or increase the air flow gms/sec to recalibrate the maf.

Mixture is very important at idle.

Check your blms for progress, or go by trial and error.

My 88 idle improved by increasing the gm/sec at MAF counts 128 , 192, and 256. I think de-screening the maf screws up the calibration.

I Added 2.1 gm/sec at 128 counts, 1.8 gm/sec at 192 counts and 0.9 gm/sec at 256 counts.

 

My tables read volts instead of counts, but I get the idea. I'll play with that next.

one more thing I've noticed: My idle Spark Advance is being controlled by the Spark Correction - LV8 vs Coolant and NOT the main spark table. is this normal or have I thrown a figurative switch somewhere?

How is the Spark Correction - LV8 vs Coolant table supposed to work?

 

Maybe you don't won't to hear it - but stalling the minute you put it in gear is all most always a load problem; ie, park/neutral switch, though SD motors seem to compensate a little better when it loses this signal. Differenct ECM's use different PINS for the signal. Crossfire's at #5 White and the TPI'S at B10, but there are others depending on what you're using. A funky signal will also cause it to surge and you will generally see a flucuating voltage on the signal wire when this occurs. You don't list your mods, but if the ECM doesn't know what the load is; ie, that it's going into gear, it's going to stall and trying to capture it on a scan with the motor running is all most impossible. Rather, capture it with the key on, engine off and simply move the gear lever to see if it's even working.

 

that's a good idea.

But I copped out and reverted back to the stock chip with minor fueling changes: idles and part throttle runs are like a champ. I haven't started it totally cold yet- but at ~85 degrees F it was like new. So odds are I just FUBAR'd the existing tune I had and there are probably no major hardware issues since it now behaves so well.

What I DID do:
* Took a stock 1989 ARAP bin, adjusted the "Injector PW vs voltage" table - I raised the value here by guessing, but must have guessed right. Seems this is the best way to raise your base fuel maps without contorting all the other tables (per Thirdgen.org). And it works.

* Then I tweaked my Power Enrichment vs RPM and vs Coolant Temp tables for mid and upper RPMs, to keep it from leaning out.

An initial test run of part throttle accel in Open Loop and dayum- 880's to 920mv's all the way through! I'm going to keep stepping up in how much throttle I use to make sure there are no major lean spots, but it's looking good, REAL good. Just goes to show you that it's awefully tough to outsmart GM....

Of course, I still haven't learned how to make a good idle though.

 

Was this to get your BLM's in line i.e. ~128? What other tables wouldn't this affect? What is the difference between this and changing the injector constant, which would seem much easier since it is only one change instead of many?


Details?

 

Well honestly I'm probably a little too naive to not be dangerous when it comes to tuning- but Batter Voltage vs PW is arguably a better table to modify because it has less ripple-effect on a $6E BIN than other methods of tuning (like going crazy with the "open loop vs..." tables and PE tables).

So you're across-the-board raising or lowering PW at idle by a substantial margin with the "battery vs PW" table, but because the table is ADDITIVE in microseconds of PW change (increased or decreased to get your idle BLMs on target), I think it has less affect at WOT because the change is additive and NOT percentage-based like the Injector Constant value is. In other words, you're adding say 200 microseconds of pulsewidth across the board- versus adding 2% pulsewidth across the board. At 6000RPM that's a big difference.

In this way, you can also keep your Inj. Constant value accurate so that fuel mileage and Duty Cycle calculations (datamaster) can be fairly close, but to what real value that is is frankly up to you.

Then, once IDLE is copasetic you use the "Open Loop vs LV8" for part throttle and the PE tables to get the upper RPM ranges dialed in on WOT (with open loop engaged no less). This seems to work quite well, but credit (and any future blame!) must go to the boys at Thirdgen.

 

I don't follow you on this. Did you change the PW vs. battery voltage for all voltage levels? Did you give more PW for a given voltage or less.

I understood this table to be used as an offset for when your battery voltage is lower or higher than the ~13.5 you should see with a proper charging system? As voltage increases the PW usec adder decreases so the injector does not flow more and make the A/F richer.

Does your battery voltage increase a significant amount from idle to WOT? Mine usually only varies between 12.8 and 13.8 at any time.

My observation has been that the fuel mileage display is derived from actual PW, not the Injector Constant. When I first installed my SVO 24# injectors, I was showing near 30 MPG in town and nearly 40 MPG on the highway. ECM was cutting back the PW because of the extra fuel, that is when I began to notice the lack of throttle response, started asking questions, scanned the car, saw the BLM's at 108, etc.

After I made the chip changes, Injector Constant being the first move of course, my Mileage display returned to a more believable value, like 20 city 25 highway.

Are you referring to 'Open Loop A/F ratio % change Vs load'?

 

gbody5:

My understanding is that, at least in $6E, the mileage IS based the injector constant (the PW is derived from the injector constant and other fuel tables)- so keeping that accurate for the *actual* flow rate of your injectors is what allows accurate MPG calculations. Now changing the Inj. Constant will enlean or enrichen your total fuel maps but as I said before the % change has a much greater impact and larger pulsewidths (like what you get at high RPMs), and it happens to throw off your MPG to boot. I prefer to leave this calulation alone for those reasons, afterall it's just another way to "trick" the ECM to add or subtract fuel. It just tends to be a more clumsy method.

The reason why you showed more MPG with the 24# SVO is because the injector itself is flowing more than the constant value said it was. The computer thought a smaller PW was getting the job done (and calculating a better MPG), even though the higher flowing injector just got in more fuel for the same specified PW... SO- you adjust the Inj. Constant for the value consistent with a larger injector (24# SVO's flow ~25.8lbs/hr or so at 43 psi), and whalla the computer is now specifying an appropriate PW because it knows that the injector is physically flowing more fuel than before.

As for Injector Pulsewidth vs Battery Voltage: my voltage hovers around 13.5-13.7v under normal operation and 13.5v for WOT (near as I can tell), but that's really not the point. You have to assume that cold cranking is going to be in the 11.7 - 12.0 v range in addition to the operating ranges of ~13.5v. I'm not concerned with the variation in voltage, however- it's simply used to richen or enlean the idle as a whole and to keep the idle characteristics constant relative to TEMPERATURE; and NOT voltage. So what I do is I take the 11v to 13.5v readings (to account for cranking to warm coolant idle values) and make them the same (say, 700 usec across the board from 11v to 14v in the table). Then while the car is idling I raise or lower them in unison to get the BLMs where I want them. Once this is done, the stock "Open loop AFR vs coolant temp" table will compensate for temperature changes. Works pretty well, and I don't think the actual voltage fluctuations during normal operation are enough to matter. it's when you get into 8-10 volts (dying battery or poor alternator) that it might be an issue. I ignore it and it works well so far. Again, I think it's probably more advantagous than other methods but also has its limitations.

However, now our PE tables and Open loop tables are still untouched so everything else remains the same- but we've adjusted basically the idle *only* for hot temps and the rest of the stock temp. adjustments are still relatively pristine and will compensate for cold starts, etc with minimal adjustment.

The reason I work to avoid messing with the Open Loop AFR vs Temp and other tables (outside of WOT adjustments), is because once you lose the relative relationships on those tables then it's a total pain to try and re-create smooth idles at all temps (in my limited experience).

Hope this helps...

 

What about the O2 sensor feedback indicating rich and thus decreasing the PW?

 

I wouldn't bother with the injpw vs batt volt.-already have tried that....
For cold start the best tune tool is a wide band-For my combo it was a must!
Something else to look at is the same tables that are in 8d-quite a few folk with lottsa mods and stall problems have taken all the stall saver values and moved them to zero-helped a lot. Go figure....
Good luck!

 

You're missing the point: it is not what the "AFR" is or what the O2 sensor does... The O2 sensor is just a nice tweek to keep things optimum. We're primarily concerned with OPEN LOOP and Wide Open Throttle situations because the O2 sensor is NOT used to adjust PW in those situations and (with few exceptions) that's where your motor will get what the fuel maps specify. In OPEN loop and WOT, that's where you worry about leaning things out and burning pistons. It's also where you have the most trouble with idle because of cold starts.

Even if you are in CLOSED LOOP and the O2 sensor is keeping things happy, then changing the injector constant wouldn't change the PW anyway because the O2 sensor is overriding it and will compensate for moderate rich/lean conditions within seconds. Then all you're left with is an erroneous MPG output and very poor tuning in OPEN loop scenarios.

So I have been trying to explain ways of adjusting your fuel delivery at idle / OPEN LOOP... AND to have accurate MPG readings as well.

I suggest searching the archives for more posts on the injector constant or browsing the archives at ThirdGen.org if this still isn't making sense?


As for the stall saver- I think it causes so many problems because I *believe* it enrichens the PW. so if you're already running rich and the motor stumbles... then you just flood it out.

 

I've done all my homework at thirdgen and more, I know enough to get my car right, and now I know why we're on two different pages. I'm talking about closed loop only and you are talking about open loop only.

I do know that by changing my Inj. Const. to get my BLM's back to ~ 128 brought back my throttle response as well as leaned out my idle (in closed loop). A little more AE fuel was required for throttle tip in on light acceleration when over 2000 RPM but I'm getting very little KR when in PE so I am not worried about my open loop situation at this point.

 

oh, sure! there have got to be countless ways to get to the same point- sounds like you had better luck than I did going the more popular route.

All I know is that I got further in two days the second route than I did with injector constants and all that. Granted, I'm a little more informed (and lucky) this time around; but it sure seemed to go smoother. As for me, I'm more concerned with open loop- simply because that's where I've always had the difficulty and where theres less room for slope because there is no O2 sensor to cover my tracks. Hopefully through our exchange someone else will have a little more to go on....

Different strokes for different folks!