hard starting when warm :please help

[mystickb1996]

so i just swapped out a vortech for a 2.1 kb on my 96 cobra. i have SCT PRP and tweaked the tune for the new blower. my WOT tuning and derivable is fine with no issues and a/f is 14.7-15.2 when cruzing. and wot is 11.3 which im happy with. when the car is cold it starts right up no problem, the only issue im having is if the car is hot and you go to start it, it doesn't want to start until i flat foot the gas pedal. then it will start because i understand when you do this the PCM cuts fuel to the injectors which makes me believe the car is getting to much fuel upon start up.
can someone help me out and explain where to go about fixing this issue? would i pull some fuel away from the MAF transfer function in the low count range? or is there a specific fuel change for start up on how much fuel the injectors pulse? the car was tuned for 60s and i didn't change injectors either and the car ran great with last blower setup.


thanks guys

 

[Don 95Vert]

Decrease crank fuel, and increase cranking air in small increments, maybe by 10-15% until it goes away. May have to hit it several times until it is better. Crank Fuel>Crank Fuel Pulsewidth and Crank Fuel>Crank ISC Duty Cycle. Sneak up on it. Don't go too far because then it may be too lean to start.

Don LaSota

 

[mystickb1996]

thanks Don i will try that, ha small world i actually bought my SCt prp from you awhile back...
thanks for the help!

 

[01yellercobra]

Do you change the whole column or just the higher temps?

 

[mystickb1996]

what column? i changed the ACT temps to pull timing for the KB because of the heat generated with this style of blower. not sure if thats what your asking

 

[01yellercobra]

For the crank fuel and cranking air.

 

[Don 95Vert]

Read Page 102 of a Tuning Guide you might have...

 

[mystickb1996]

Ha I got your tuning book, and I just set up the tune by pulling 10% fuel from crank fuel pulse width. For the crank ISC duty cycle the values are set to .992 already and when I try and add any it says limit reached

 

[Don 95Vert]

Then just do the fueling...

 

[01yellercobra]

Read Page 102 of a Tuning Guide you might have...

I looked at page 102 and it didn't have anything about this subject.

Ha I got your tuning book, and I just set up the tune by pulling 10% fuel from crank fuel pulse width. For the crank ISC duty cycle the values are set to .992 already and when I try and add any it says limit reached

Have you dialed this in yet? If so how much fuel did you pull? I'm around 40% and still haven't issues. But I'm only pulling fuel and adding ISC for the ECT's above 100 degrees

 

[ugotbit03]

Not to hi-jack, but since we are on the subject...

I'm experiencing something similar. Colt starts are great, but hot starts the car catches, then dies. If I open the throttle blade a little bit it will restart.

I tried adding 10% to the ISC crank duty cycle with no luck.

I also noticed, After it's re-started after a hot soak it will be LEAN. AFX only goes to 16:1 and it's pegged and slowly drifts down back to commanded AFR after 2-3 mins.

Just seems odd it acts like it wants more air but then is lean.

Any ideas?

ETA- this is forced O/L with adaptive off

 

[01yellercobra]

Maybe the lean reading you're seeing is the extra fuel that's moving through the cylinders. I've heard of mixtures being so rich they show a lean reading on the wideband because of all the oxygen in the extra fuel. Maybe try reducing the fuel as well.

 

[ugotbit03]

Maybe the lean reading you're seeing is the extra fuel that's moving through the cylinders. I've heard of mixtures being so rich they show a lean reading on the wideband because of all the oxygen in the extra fuel. Maybe try reducing the fuel as well.

I'll give it a try, but it's not acting like its that rich. Call me crazy, but I can hear the difference in the exhaust between 13:1 and 15:1. It sounds more crisp when it's lean at idle, and sounds that way upon re-start.

I found a post on the PRP forum by a poster named Skud, he said he was having similar problems and he changed the "Transient Fuel Temp Based Fuel That Is Trapped" table by 20% and it showed improvement. I hit the table with 20% and there was no change at all.

 

[01yellercobra]

I was reading in that forum and found a post from a guy that scaled his crank fuel by the percentage difference between the old and new injectors. I did that yesterday when I got home from work. Cold start was a little rough this morning so I might have to add a little bit back for cold start. But I stopped by Arco to get something to eat and when I went back it fired right up. It hasn't done that in a long time.