TRU-2GM

iTrader: (6)

I recently did a ls6 swap with a big cam, big stall, LTs, along with the FAST 90/90 combo.(stock displacement) Ive done the return spring mod to the TB as well, that is for sure closing. Now i have the car idling perfect, sitting in both park and gear idling perfect. I have been messing with the "cruise control" i have been getting and got it down pretty minimal right now. Its still needing some work though. Heres what the car is doing: in different situations:

--braking hard it will surge the rpms down to 400ish and then correct and idle normal.

--while giving it a little bit of gas to move and you let up it will surge the same way

--anytime u give it a little punch and let off real quick it will 100% die everytime

You guys recommend anything? I am up for any help. Thanks in advance.

p.s. fm14 cam 4200 stall.

TRU-2GM

iTrader: (6)

anyone??

2xLS1

iTrader: (25)

There are so many different parameters to edit for idle tuning that without knowing and seeing everything you've changed and without seeing a log file, it is going to be hard for anyone to tell you exactly what needs to be done. Just for starters, what are your IAC counts both in gear and in P/N?
Just curious, what is the return spring mod? Haven't heard about that one.

jimmyblue

iTrader: (11)

Log your dynamic airflow number at idle and make sure
the base airflow tables are maybe 90% of this (several
modal tables to be trued up). Having airflow close to
what's needed will act as a "backstop" for the RPM
control loop. This thing all by itself took care of almost
all of my surging / bouncing (except I have some on
very cold mornings, I haven't done much with the lower
ECT ranges since I seldom see them).

The drop on braking / blipping I think may be your throttle
follower not bumping the air enough. This may be more an
"effective area" problem relating to the different TB's IAC
passage / plunger geometries. Check around for people
who have been messing with that aspect. There are a few
idle tuning writeups out there (I haven't read them).

TRU-2GM

iTrader: (6)

With the car at idle in P/N the IAC is 20-30 counts. In gear at idle it is ~50. That is with ECT at operating range. There is higher counts the colder the motor is. I will post up logs or provide values if that will help!

With the crappy FAST TB a heavy duty return spring is needed just to close the TB and prevent it from sticking open when you let off the throttle.

TRU-2GM

iTrader: (6)

It shows ~0.15 g/cyl Dynamic Cylinder Air at idle. So what are you suggesting the RAF be at? I've logged the STIT, LTIT Gear, and LTIT PN through the entire operating range and used a spreadsheet on here that calculated the RAF numbers. At operating temp I'm at 7.93. Do you agree with that?

I've tried a whole range of numbers in the throttle follower with no success on the rpm falling at a stop. One thing I did notice is that every time you brake hard the MAP spikes up and the rpm falls. Do you have any more suggestions? Thanks!

ringram

I vote for cracker and follower.

You can check to see if the cracker is operating a very slow speeds, sometimes it gets cut too early, you can put a tad in at slow speeds to act as a backstop to prevent engine stall when it overshoots.

Also check your follower decay rate approaching a stop you might want to reduce its decay to cusion its action.

TRU-2GM

iTrader: (6)

Thanks for the suggestion but I've tried the cracker and follower tables. There is something else causing this. If you hit the throttle in park it drop really low before it recovers.

TRU-2GM

iTrader: (6)

lotta lookers...nobody has anymore info? Ill take anything i can get right now...

TRU-2GM

iTrader: (6)

back to the top...anyone?

98redorangeta

iTrader: (10)

seems like every time you go back to your lower ve cells it has a problem not when you sit there and its ideling just initally hitting the cells maby a little ve tweaking would help just a thought.

dynocar

Once in awhile we get an aggressive cammed car that the vehicles O2s will not function correctly and read too lean because they are too cool in a header collector at low RPM and idle. This will cause us to miss tune this area too rich and cause similar problems. Sometimes fresh O2s solve this problem, once we just simply had to keep the car in open loop.

EJ

TRU-2GM

iTrader: (6)

both 02s are brand new now. One was messing up on the board so I went ahead a replaced both of them with brand new ones. and I have sims for the rears.

dynocar

I don't like guessing at other peoples problems and am probably way off base here but, against my better judgement, I'll continue. If the O2s are not staying hot enough, often new ones will not solve the problem. If a tuner does many radical cammed engines, sooner or later they will encounter this problem. Sometimes it's the engine combo and the placement of the O2s in the exhaust stream. This condition seems to happen with long tube headers with the O2s located in the collectors. Experimenting with a higher idle RPM and decreasing the idle timing will help keep the O2s hotter. The higher idle speed is touchy with an automatic and a stock tight stall converter. I've had some that would not work under a 1000 RPM idle.

EJ