hi all

i built a 396 wiuth 10.6 to 1 comp, AFR 210cc heads, and 234/238 288/292 112LSA cam...the intake is a single plane EFI

when it was warm, the car started immediately, and idles nice..

now, its getting colder, and when i start the car, i fires up immediatley, runs, got slower, and then dies from overfueling...

when i start again, i have to push the pedal a bit, then car catches slowly, emits a cloud of grey smoke and then i have to coax it a bit to 1500 rpm, after a half minute, i can let off the gas, and it idles nice on 1000rpm, until it got warmer..

my question

the ECM is the SD 727 type, with the $8D mask

which table do i have to modify to make it running nice

thank you

 

Sounds like several things could help.
1.)You may be seeing overfueling due to spark being removed when cold.
a.) The table "Spark Advance Temp. Correction Vs. Load Vs. Temp." located at L813B-L81A6 could be tweaked so you don't remove as much spark when cold.
there is a bias value for the table that is 20* so the table values actually are 0* different than your main spark table settings if the value is 20*.
b.) "Closed throttle SA vS. RPM" located at L81FD-L8209 could also be used if the spark is still low after warmup.

2.) Having to push the pedal a bit indicates not enough air on cranking. Resetting the IAC and TPS, after adjusting the minimum air (mechanically) should aid with that. Tech page has the procedure if your not familiar with it.

3.) You could bump the "idle speed Vs. coolant temp" table if desired at L8632-L8642

4.) The "AFR % Change Vs. Coolant" table may help if you want to change the open loop commanded AFR in the cold areas.
Located at L845E-L846E

To idle at >800 rpm in $8D (if it is AUJP, not in ANHT) you must adjust the idle speed limiter. Not sure what you have so I thought I would throw that in.
https://www.thirdgen.org/forums/diy-...ter-730-a.html

Try anything and everything, see how it behaves.
HTH

 

Might also look for the choke decay rate.

 

Hi all

thank you for your suggestions!

one thing i have to clarify...

when i start the car (after sitting a while) it runs instantly, without pushing the gas pedal.....then while idling, the idle slowly decays and finally the car stall

when i start again, after this event, i have to push the gas a bit, to clear the flood....

i also think, i have too much AE when cold....

the IAC value seems to be fine, according to datamaster...

@JP86SS

i know which table you mean.....my idle SA is now set at 24.6° (closed throttle SA vs rpm) so, AFAIK theres a correction factor in the table you mentioned....
My idle speed is set a 1000rpm when cold...

the broadcast code use, is ARFP, the car is a 1990 Corvette, six speed if that matters..

anyways, i will try it, and im happy for every information i get


thank you

 

I am guessing you have injectors bigger than stock. Did you decrease the Crank BPW msec time vs. temp for larger injectors? A lot of it could be from Crank BPWs.

 

I would say that if it starts and runs good for the first 10 seconds or so then the crank PW tables and transition parameters are ok for now. Its probably something in the VE tables, or startup AFR/spark thats causing it to puke. Once warm, the ecm will enter closed loop and correct for any fueling issues.

 

Hi!!

i´running 42# injectors, i know, they are on the big side, but i got them new and cheap, and i also have a friend, who drives 42# inj on a stock 350 without problems...

no, did not decrease cran PW tables...

it runs fineafter starting, and it catches instantly, and then the rpm begin to drop slowly, until it stalls..

the interesting thing is, when i coax with the throttle, after abut 20 secs, it idles perfectly....

so, it seems, the overfueling only takes place at startup...

i will try the Spark thing first..

to Closed loop.... when the engine is warm, i have a 124-128 BLM at idle...so, this seems perfect...

i have to look for a table, that makes a lot enrichment when cold,maybe the AFR % Change Vs. Coolant (open loop) should be adjusted....

thanks again

 

42#/hr are fine for your setup. You need to decrease the Crank BPW times. They are still setup for the 24#/hr so you are pumping 2x fuel than you need at Crank. I would do a global remove of 600us to 800us to the Crank BPW vs. Temp. 2D table and see if it helps.

After doing the Crank fuel change, then look at the ALDL Target AFR and what your (heated?) O2 sensor is doing. Do you have a WBO2 sensor? That would help for doing the Open Loop AFR adjustment. If your lower VE table is correct then the open loop AFRs should already be very close to correct. If you don't have a heated O2 or WBO2 then look at the injector BPW in the ALDL to see if it is giving too much fuel......or post a log with RPM, MAP, TARGET AFR, BPW.

Is that a stroked 350ci or a destroked 400ci?

EDIT: I run Ford green 42#/hr on a 350ci with LT1 intake, 216@.050" I/E, 110*LSA, TPI exhaust manifolds

 

Have you datalogged in the area that it has the problems? The engine may be getting into some funky areas when the ECM tries to idle down. I was having this issue with my PCM and the fuel table being off. The car would start well, but after a minute or so when the computer entered closed loop idle, the engine would hit a lean spot and die. The datalog paramters will help guide you to the spot or spots that are causing the motor to die. It could both be fuel and spark. As far as the cranking stuff goes, thats only used during initial crank and the ecm rapidly transitions off of the crank tables and onto the main VE tables for the base fueling once the engine starts. If the problem takes more then 10 seconds to come up, then look elsewhere.

 

Thank you!!

yes, i have a WBO2 and i will try it out...

i think, my lower VE tables are really good, and the car starts fine...

anyways, i will give the Base cool.adv. corr. vs load vs Temp a shot, the Crank fuel vs coolant Temp

i think, or i hope, i can tune it out...also, i take a look at my AE tables, i think, theres too much AE when the throttle is moved a bit...

that is a stroked 350...based on a GMPP block

i also would say, im within the 10 secs....so, my focus would be on the mentioned things...i will try out tomorrow, and let you know..

thank you

 

Remember to keep it simple and only change on thing at a time. If you are sure your problem is ONLY related to the cooler temperatures, and only right after start up then my first place to make changes would be "Loop open % change AFR vs Temp" (this is the table name using super-AUJP xdf)

 

Yes, narrow it down to one thing. The problem is that he has way too much fuel during crank to begin with. Once the Crank problem is solved, he can work on the "after start" problems. The crank fuel problem will not solve everthing, but it will help.

 

ok, im getting lost...

i changed the tables, mentioned above, bumped up idle a bit, and the starts and idles nice...

but, the next problem is here...the car idles nice, i blip the throttle a bit, engine revs nice, comes down and stalls....

if i let of the gas very slowly, it idles again...

where should i look now?

please help

thank you

 

Did you start with a stock bin or a SAUJPv2 bin? The SAUJPv2 has a lot of the throttle follower removed.

It sounds like the lower KPA (20-40 KPA), lower RPM Vol. Eff. (VE) tables are off a bit or too much throttle follower (IAC) was removed.

Both will cause the stall when hitting the throttle and letting off. If the IAC throttle follower is at the stock setting then I would change the VE in the 20-50KPA areas (you probably idle in the 60KPA+ range).

 

The problem is likely somehwhere other then the crank tables if its repeatable like that and only happens after startup. Check the VE and timing tables. You also need to datalog with a computer and a WB if you have it. Look closely at the SA and the AFR. Its likely the fueling or spark are off in portions of the tables. I believe there is a one column closed throttle SA table as well as the main SA table in the TPI ecms, so dont forget to look at both.

 

Maybe I misunderstood. You now have the start and stall problem fixed using the crank and AFR table adjustment, right? The next problem is the stall after hitting the throttle and letting off? If true, then it is like dimented24x7 said and the lower VE table needs a tweak or too much throttle follower was removed. Has the closed throttle timing been bumped to about 25 degrees?

 

Hi all

i think, my problem is solved, i tweaked Spark correction, AE tables a bit and very interesting, the decay rate was wayyyy off,,so, when i hitted the throttle, AE was given, but not taken out..caused stalling...

this forum is a pool of knowledge, and i want to say thank you to all who contributed