Basically, i put a little bit too big of a cam in my truck(90 suburban 3/4ton 4x4th400, 7747 computer) and now it has a fairly low vacuum reading at idle. Runs pretty much normal everywhere else but maybe a little down on power? So here's the deal. So far i have adjusted my BPW down to 130 from 135 and taken around 80% of the fuel away in the main ve table from 30-70kpa and 400-1200rpm. I have also added around 4* of timing in the same cells. After all that my BLM's are still around 112-125 which tells me i need to take away even more fuel! Does this sound right? the cam i put in was pretty mild with an operating range as advertised from idle to 5500rpm. Does this sound normal?

 

Got a leaky injector ? Pretty common on those old TBI truck to see injectors leaking.

 

What is the VAC or MAP?

Yes you are correct. BLM < 128 ECU is adding fuel. Cam may be fooling the ECU to do so. How is exhaust quality? Smell? Try a white hanky over pipe to test.

 

Are the injectors leaking, fiarly common problem.

 

Seems to idle around 42kpa in park. Thats with the distributor bumped to about 6* base timing. Exhuast smells rich.



Here is the stock(or what i think is stock) settings for my truck,



And here is how far i have adjuted mine! And its still seems rich! BLMS around 125 or so.

 

Here is links to the loggs.

http://coloradok5.com/forums/showpos...9&postcount=68

http://coloradok5.com/forums/showpos...&postcount=173

 

Does your bin allow for adjustment of the 02 thresholds and constants?

This might help with the idle:
https://www.thirdgen.org/forums/diy-...ome-those.html

The other thing I did to mine was to tighten up the target deadband at idle and to add more timing in.

 

Im not too sure really. its a 7747 computer with an amur0055 bin. Going to read threw that link you gave me right now.

 

That thread had tons of info in it! Trouble is, seems most of it pertained to the 730(i think) ecm. I will have to see if changing the o2 settings are adjustable with the 7747 in tunerpro.

 

So it looks like all i can adjust is the "idle speed deadband" and te "stoichiometric afr" Think it would do me any good to mess with those? the deadband is 12.5 right now and the afr is 14.7:1.

 

Scratch that, looks like i can adjust the rich/lean/mean thresholds! So could it be beneficial for me to adjust any of those perimeters?

 

Here is my tables,

 

why is your idle set so low at 575 or so? and why is your VE table so lean across the board? like only 55% fill eficiency?

if you have a big cam, I would start with moving your idle to like 675 or 700 or so. above 50* c. maybe a little higher when the engine temp is a little cooler might now be such a bad thing. say like 800rpm at 30*C and 1000rpm at 0*C to bring it up to operating temperatures... if that makes sense.

your fill efficiencies are evenly lean. that doesn't make any sense at all... your table should have a "definite" curve to it. you should be able to "know" what that intakes air flow looks like... at least that is the impression i am under having only started tuning mine. ?

do you have a "lower VE table?" my PCM has 3 sets of tables... one for idle (under 1600rpms) and one for all rpms to 5600rpm, and then another added in for up to 6400rpm.

 

Mine has the main ve table and the ve adder table. Added up they seem pretty normal for a stock tune. The idle is also stock but in reality, it never idles that low. Infact it idles a little on the highside for my liking. Around 850 or so hot in park.

 

oh... that makes sense now.

 

I think my exhaust smells a tad rich too...

I got a little bit of a lope to my exhaust at 600rpm, and my VE tables are mostly correct coming from an O2 sensor reading. but I think i may have some unburned fuel gas mixture at that temperature affecting my O2 sensor reading. *shrugs*

I had a bit of knock issue at 600 rpm too. *shrugs* i just adjusted my idle up to 675 and now it runs a tad bit smoother and the slight knock went away. and at 128/128 int's/blms. *shrugs* wasn't what I wanted to fit it, but if the shoe fits....

btw, if your BLM's/INT's are off of 128 your definately either rich or lean. keep adjusting until you get them to synch up to it.

 

Last I looked I idle at 40 MAP. Steady at 750 rpm this morning. 224/230 @.05 with a 114 LSA.

You can try moving the lean median rich thresholds. I in fact richened them a couple years ago but yesterday(coincidence) I move them closer to stock yet still on rich side for values. However I idle OL. Right now I am 50mV toward rich. You may want to try same but move to yean all three same amount and see what happens. If not much change try 100.

what is idle speed deadband?

Stoich I have set to 14.3 for E 10.

why are you running so much timing at WOT 100 MAP? 42 deg plus a possible adder????? OOPS directed at Y5 ......

 

I'm still not quite sure what the deadband is but mine is set at 12.5. I should clarify that the tables listed above are stock, unmolested tables for a 7747 computer using the the amur0055.bin. the thing i still need to read in now is how the commanded afr and the r/l/m o2 thresholds work with each other.

 

Oh it looks like you were referring to my other screen shot showing my modified tables. That spark table is one of the generic "performance" tune timing tables that i plugged in there.

 

My R/L/M threasholds and idle deadband stock settings,

 

heres cam specs
Basic Operating RPM Range: Idle-5,500 RPM
Intake Duration at 050 inch Lift: 204
Exhaust Duration at 050 inch Lift: 214
Duration at 050 inch Lift: 204 int./214 exh.
Advertised Intake Duration: 262
Advertised Exhaust Duration: 272
Advertised Duration: 262 int./272 exh.
Intake Valve Lift with Factory Rocker Arm Ratio: 0.420 in.
Exhaust Valve Lift with Factory Rocker Arm Ratio: 0.442 in.
Valve Lift with Factory Rocker Arm Ratio: 0.420 int./0.442 exh. lift
Lobe Separation (degrees): 112
Intake Valve Lash: 0.000 in.
Exhaust Valve Lash: 0.000 in.

Pretty tame but i think its still enough to throw the poor ecm out of whack on the stock tune. So, my BLMs are in the toilet (105) at all times during idle. Off idle they pick back up to around normal. I think what would probably be best, is to take away 20% of the fuel in the main VE table at idle conditions, add 20%timing at idle conditions, and adjust my R/L/M o2 threasholds and possibly mess with the open loop afr just a tad. What say you dudes?

 

You are already at 33 deg at idle(600rpm/40map). You would add more?

When you wack throttle and RPMs climb do you see KC's in your logs? Seems like a lot of timing for a heavy vehicle. Fast355 posted timing tables for his heavier vehicles frequently. Might want to search for his tables.

The RPM deadband I will guess is a range above and below commanded idle where no correction(SA-IAC steps) occurs.

yes You need to pull fuel at the cell idle you idle in as well as surrounding cells. 02 values could be dropped (rich median lean) to force leaner. I would do each individually and note result. Check the def file to see what other tools exist for idle control.

I believe you can force OL idle(0%TPS) only. That is a possiblity. May have to do search to find out how to add it to the file.

 

So probabably, for now, dont dick with the timing, force OL at least at idle, pull fuel out as required to get it running right, THEN add closed loop back into the mix and adjust the R/L/M threasholds if the o2 throws me back out of whack? Sounds good ya?

 

Yes I agree. When you adjust the thresholds since you are rich(I never was...I was lean) move them reduce them all in increments of 50 mvolts till you see a change. I may take greater than 100 mvolts to see a change.

 

Ok. And when i do get to changing the thresholds, do I also need to be changing my commanded afr?

 

Yes. Mine are at 14.3 for E10

 

And is that across the board? Or just at idle?

 

across the board. I am struggeling with idle A/F. Sitting around 13.3-13.5. I keep pulling VE fuel at and around idle cell. little change. OL table shows 15.0. Maybe my BPC is off at that Map area. I need to calibrate FP to MAP to properly set my BPC. I borrowed the table from another member with same VAFPR and engine.

 

Cool man thanks for the help!

 

Man, if i studied this hard in school, i would have had 4.0 gpa! Just read too much again here,

http://www.diy-efi.org/gmecm/papers/747fuel.txt

Awesome info but pretty confusing cause it all seems to be termed in hex code.

 

You will get used to it if you intend to be successful.

 

You & mistaben both need to be 200% sure you have NO exhaust leaks.

 

I certainly do intend on being successful! Thats why i have been studying like crazy! As far as exhaust leaks, i really believe i am perfectly exhaust leak free. I suppose its possible that i could have one, but i dont think i do. The main problem with my truck is that it will run almost just like stock normal but when you come to a stop light, it "loads up" and goes into a surge. While it does this, the IAC opens up wide and eventually saves it. Most of the time. Other times i gotta tap the gas for it to quit it and then it will just settle back down and then repeat the surging episode. All of this i believe is caused by at least one of two things. A) the cam has too little LSA and the vacuum suffers as a results and tricks the computer into thinking it needs more fuel for its "load", and/or B) that the cam has too much over lap and is letting the o2 sniff a little to much fresh air thats being pulled straight from the intake valve into the exhuast valve. So, With my new found knowledge, i think i have a better plan of attack that i think should end with good results.

 

Ok so i just burnt my "second try" chip. What i did for this one was took the stock amur bin, reomved 20% from the 400-1200rpm 30-70kpa and forced open loop. This way, i can see how it behaves with/without the o2 sensor chiming in. Also added 10 gallons of fresh fuel and a bottle of the yellow heat. I should have time to run it tomorrow.

 

Well that SEEMS to have made it a little better. I ended up with near nothing again in the VE1 idle cells. I switched the o2 back on and let it go closed loop and my blms dropped like a rock to 108 again! I think im going to combine the VE1 and VE2 tables and zero out table VE2. Then start removing fuel from the combined setup and see what that does for me.

 

My question is how much is too much fuel to take out? If i end up taking 70% of fuel away at idle just to correct for a slightly above stock cam is that too much? Also, do i need to take away timing when i reduce fuel so much?

 

Ok guys, i have been hard at it for a while now! I got the truck running pretty good and its right around 128BLM at idle! Trouble is, it still doesnt run quite right. Still feels kinda rough. I have read on here about this very condition where people have set everything up just right with their BPW, VE tables and so on, but the motor still ran rough. In these cases it seems like people were able to change there o2 threasholds or switch to open loop idle and change the open loop idle AFR values.

From here,

https://www.thirdgen.org/forums/diy-...lp-me-get.html

and here,

https://www.thirdgen.org/forums/diy-...ome-those.html

I guess my question is, should i dick with these settings, and if so, which direction should i take them? There was also talk of tightening up my idle deadband. Mine seems to be at 12.5 right now. Does that sound right? Should i mess with that?


As a secondary question, i would like to get my IAC closed a little more and have my blades open a little more. To do this, do i need to change the IAC steps or will the computer figure it out as it tries to match up with the desired idle speed?

Here is some screen shots of my current settings in TP,

EDIT: dont know why the pics show up small here. Let me know if you want links to the originals.










And my most recent data log. Keep in mind this is just sitting in my driveway idling.

Thanks very much guys! I have spent so much time on this site now just reading that sometimes it does feel like my brain is melting...

 

Looks like i never replyed to this question. My bad. I dont believe so. When this all started i had the injectors rebuilt and flow matched with no difference in the running condition of the motor.

 

As I stated earlier I am now 5% richer on the lean/median/rich swing points. that is not much. E10 my stoich is set to 14.3. I dont think above makes much diff. I would run stock settings unless you have a good reason to change. I see mine today are at 40 MAP lean .44 mean .46 rich .49


I see your VE adder table does not add any fuel over 3200 rpms? I believe it should. That table was prob zeroed out to aid in calcs for BLM. someone zerowed out all rather than just above 3200rpms. It was said(Grumpy) there should also be a small value in 400 rpms. I dont know why.

I would reduce the IAC steps at 160dF-200def to 5-10. Then use TSS to set idle as you like. I did that to help control rolling idle. I did other things as well.

Refine rough. What does the datalog show during rough? 02 swings-INT moving.

 

Ronny, thanks for the quick reply! You are right about the VE adder table not adding anything above 3200rpm. I was told then when i did that the computer would run off the 3200rpm value on up and that it was normal. The small value at 400 rpm, are you talking about in the adder table? Or the main? By TSS, what are you refering too? Here is a few screen shots of loggs, First is just one that i edited to show the column values,



This is it being "rough" in park,



And one of it being "rough" in gear.



Now keep in mind that it behaves this way all the time. Its not an event that happens sometimes. It just idles rough. I have a few videos but none of the latest burn so they arent quite accurate. I can post them up anyway if you want?

 

Also, i should mention that it will almost exclusivly idle in closed loop in park and open in gear. Not quite sure why but obviously there is some peramiter in the chip set that way, im thinking its these

 

If you never drive over 3200 rpms all is well. I would add fuel to second adder table.

In gear the MAP is lower. In park it is higher(less load). that may be diff? RPM also could be higher in P but thast can be set to same as D.

400 rpm adder table needs a value.

define A-M for title in log. some I know already.

 

A-Time
B-Prom id
C-IAC
D-Coolant Temp
E-Speed
F-Map
G-rpm
H-TPS
I-INT
J-O2
K-VOLTS
L-KNOCK COUNT
M-BLM
N-RICH LEAN COUNTER

 

Yes a large cam 50-55 MAP. That means even a WB will be fooled at idle as well as low load areas of the tables. may want to search further for thrreads that address large cam concern. At idle do you see PW flippin synch to asynch? Do you see SA changing at idle? See sticky in TBI for "free tune". Good reading. go to dynamicefi.com and read intro to tuning part 2. Same good read.

I am also OL at MPH < 20. Only cause the transition from dead stop(manual trans) is better(for me).

 

I think you might have to "feel" out the idle quality settings that you want. I believe that I also modified the IAC steps from stock (added a whole bunch more) and also messed with the dead band a few times before I got it where I wanted it. I took me a few burns to get it just right.

On my TPI $6E motor, I have the Target Speed Deadband for Drive at 25 rpm and 50 rpm for park/neutral. I tried 12.5 but it was too choppy and would jerk at lights.

I even was able to reduce the idle speed throughout the coolant temp range, it idles really low and tame. I am not sure how much tweaking you can do with the 7747 ECM but its worth it if you can get the idle just right.

 

Is "deadband" that range of rolling RPM that can exist B4 IAC steps or correction begins?

 

After 5 years and hundreds of chips trying to get the shake out of my idle, I finally bought a wide band. Should have done it years ago. A lean misfire will show up as a rich condition and the computer will take out even more fuel making it worse. Everything i read said take out fuel with a cam. I ended up adding fuel at idle. A lot of fuel under 1000 rpms. Awesome low end torque. Now I gotta get some better tires.

 

What did you do to add fuel? VE tables?

 

synch to asynch isnt something im familiar with just yet so im not too sure about that. SA=Spark advance here right? That i imagine changes slightly but should be due to my main SA table. I have checked it with a gun and its about right where the computer says it should be. My deadband is 12.5 still currently. Really wishing i just would have saved up for an emulator at this point! Pulling and re-programing the chip is already starting to get old!

 

Alight so, this Tuesday the 20th is my birthday. So im taking the day off from mork and everything else and im going to do nothing but work on the truck all day! Going to start the day by double triple checking all the mechanical stuff like min air setting and timing. then im going to burn and burn and burn chips all day! Going to start with stock (combined) ve table, and stock timing. Then, im going to to get my idle blms close to 125-128 using my BPW. From there i will fine tune the ve table and add in some timing. From there, i have a hunch that i will be fairly close to where i am now but a little better off. I think that i will still have to adjust my open loop AFR and/or my R/L/M o2 threasholds, as well as my idle speed deadband. After all that, im really hoping that i will be back in business! So, on the 20th, expect many MANY questions! Its going to be both a frustrating and glorious day all at once. Pretty stoked tho to have gotten TP to read my data! Means i wont have to dick around with opening and closing winaldl to witch to tp and back again!

About the timing. I know one thing for sure, its messed up. I have been running my physical base timing (tss wire unplugged) anywhere between 0* to 12* advance and have never changed it in my chip. What effect would that have on my total timing? Say for example, i set the distributor at 8* advance, initial in bin at 0* and had my main SA set to like 25*. Would that put me at 33* advance? Now if i had dist at 0* and initial in bin at 0* and main SA at 25* i would have 25* right? So i guess my question is, what if any purpose would be served in advancing the distributor if its just going to coincide with the computer anyway? Leads my to believe that if you have it set at 0 at the dist, 0 in the comp and 25 in the table, its the same as 8 at the dist, 8 in the comp and 25 in the table. Am i way "off base" (get it!? PUN!) here or am i kinda right?

About the Rich/Lean/Median o2 threasholds and afr. Right now, at idle, the blms are almost right at 128, but, the motor still "shakes" and runs "rough" not to an extreme degree but its very noticeable and unpleasant. The exhaust smells very rich and the plugs i have yet to pull but i suspect they will be fairly black also. So, which way should i take my AFR's an o2 commands? I think i need to either add or subtract 50-100mv from all three o2 points and i need to add or subtract to get 1 point(ie 13.7:1 or 15.7:1) to my AFR's. Trouble is after all the reading i have done, i cant figure out which way to go with them! Anyone have any advice in that department?

Here is a list of all my scalers, and tables,







And just for some fun here is a couple pics of the truck!