bwolfZ28

iTrader: (40)

I'm having some issues with cold starting my car. Mods are as follows:
TFS220 Heads
Custom 234/239 .620/.638 112+3
Fast 102/92
Stock Shortblock

The car was dyno tuned and runs like a freight train when cruising and at WOT but the thing stalls like crazy when cold.

When I first go out to start the car it will fire and then immediately die unless i give it some gas to keep it running. It will NOT stay running alone unless I give it gas and keep it around 1500rpm. After keeping on the gas for 20 seconds or so it'll finally idle but begin to surge. I was messing around with the scanner and If I put the AFR control at 15.5 the surging goes away. I'm thinking that it has too much fuel? Also how would I go about changing these values...Do I just go in and change the Open Loop Eq table as necessary? I would really like to figure out this cold start issue since it bugs the crap out of me. The car runs and starts great when its warm.

Also, another thing is that periodically after driving and when coming to a stop it wants to die...the other night in the drive thru it wouldn't idle for the life of itself. Is this due to a big cam running off the 02 sensors at idle? How do I go about running it strictly on open loop say from 1200-0 rpm? The car runs great but these little driveability issues bug the crap out of me. Like the car dying when doing parking lot manuevers, like going from reverse to 1st etc...

I'm slowly learning the HP tuners but please forgive me if I ask any questions that might sound stupid. The car was dyno tuned with the mods above with the ls6 intake and then taken BACK and supposedly retuned for the Fast 102/92 but it seems to have nothing but issues. Any help would be appreciated. I can post up the tune later when I get home.

thunderstruck507

iTrader: (18)

Mine behaves similar so I would also like to hear some input.

But even more peculiar, mine can warm up from a cold start and will still surge a bit once it's warm (even if I drive it all the way across town at operating temp). But if I kill it and then restart it 20 seconds later even at only ~180*, it runs fine. It doesn't do this in warm weather.

bwolfZ28

iTrader: (40)

Mine does the same thing every once in a while. I hope someone can chime in and help us out.

thunderstruck507

iTrader: (18)

As a temporary band aid, I adjusted the temp based idle rpm table to make the car run at a higher rpm and drop steadily as the ECT comes up.

It works for the most part, but seems like a ghetto fix and I would prefer to fix it a better way.

jimmyblue

iTrader: (11)

This comes from your "dyno tune" consisting of nothing
but "big end" timing and fueling twiddling and a big bill
for roller time, most likely.

Your cam really bent the low RPM VE, making the PCM
think more air is coming than really is, and that doubles
down on the cold start enrichment (and idle air errors >
idle fueling errors > idle instability).

You probably will want to take out some cold enrichment
at MAP levels where you idle, but you won't even see the
real, right idle MAP until you take a pass or two through
the VE table to at least get the warmed-up fueling close.

And if you use wideband or narrowband sensors to say
if you're fueled right, with a big cam and idle-range RPM,
you'll be wrong. Because the exhaust is full of air that
fakes the sensor lean, so you'll compensate by higher
VE numbers and be stuck with excess fuel (that reads
right, but runs wrong).

I propose that you tune to minimum MAP, not any
indicated AFR, for idle range air mass - and then put
the O2 voltages you get, into the closed loop switch
point tables - and forget trying to use magical methods
like pasting error histograms, when they're full of error
terms you can't get a reading on.

Slowhawk

iTrader: (12)

102 fast= issue's - very common.

I personally do not like them because the do leak through the pours in the intake. Throttle by wire catches it, IAC is too slow to catch it.

Now that the rant is over.

You can up the idle air flow table about 20% in the colder area's and see how that does.

Another is to make sure the iac count is 40-80 on hot idle. Set that accordingly. If it's high like 130+ there could not be enough airflow through the iac on cold situations.

bwolfZ28

iTrader: (40)

My IAC at a hot idle is roughly 15-25 with most of the time being on the bottom of that scale. Here is a copy of the tune so if anyone wants to look it over feel free to chime in. I will see what I can do to get the VE to the lowest MAP reading. It seemed like the motor loved being at 15.5 on the AFR control and it didnt surge at all.

bwolfZ28

iTrader: (40)

So i just went out and all of my intake bolts were loose. I retorqued them to spec and I turned my TB blade down and NOW the car will idle at 55 IAC counts. Could this have been the whole problem or do you think my fueling is still off?

bwolfZ28

iTrader: (40)

Here is an idle log. I'm going to drive it now to get a log of driving. I got the IAC counts where they need to be at idle.

thunderstruck507

iTrader: (18)

Thanks Jimmy, that makes sense. I know when I was trying to do the tuning it was reading bad lean at idle so I kept adding to the VE there so I guess I can go back and try to redo that area of the table and also look at the cold start enrichment.