RonSSNova

iTrader: (3)

I installed a new engine in this car here at the shop.
I have no experience with it prior, so I don't know if it started cold prior or not.

I have not altered the tune that would affect cold start as far as I know. I've just done part throttle and wot tuning.

What I see is that the IAC position is at 0 when I try to start it cold.
IAC desired is at 0 as well.

The cranking pulse goes rich as expected the first time I try to start it. Sometimes it starts, but really struggles.
If I shut it off and re-crank it, the pulse width goes to 20-30ms and stays there.
It's flooding itself.
It does seem to be following the cranking pulse fuel table, commanding approx. 8:1 AFR.

TB is a BBK 90mm.

Kind of lost! It will start if I floor the pedal......and restarts fine when warmed up.

Injectors btw are unknown short fat things. Other than data from the original tune it came in with, the injector data is all stock except for the flow rate. I don't even think that was correct, but it ran. It's a pretty much hacked tune......I'm trying to correct all that.

So question:

Shouldn't the IAC go to 310 park position?
I've disconnected it, cycled the key to reset it, but it seems to want to stay at 0.
Once it's running, it begins to open and ends up at 310 then works it's way down as it warms up as expected.

Ideas?

Ron

JakeFusion

iTrader: (7)

Yeah, if the IAC Reset Position is set to 310, that should be the start position. If not, then I'm not sure what would cause it to open up all the way. But if it's open all the way, you'll have to essentially flood the engine for it to ignite (as you're seeing). Have you tried a different IAC? If it's working as expected after start up, it might be fine. Weird.

A possible bandaid would be to set the 400 column at 100-105kPa in the VE table like 10-15% richer. It always seems to hit there on startup and if I lean out those cells, it does get harder to start. So that's a hack answer.

I'd also write full to make sure the tune isn't corrupted in some manner.

psiconversion

iTrader: (5)

Sounds like your coolant temp. sensor is open, reading -38*. Check the reading on your scan tool.

JakeFusion

iTrader: (7)

That may be the answer right there.

psiconversion

iTrader: (5)

Let me know what you find. Thanks.

RonSSNova

iTrader: (3)

Thanks guys.
Since I've come to work for this shop, I tune Mopars......don't hit me! Ha.
I don't have my log files here for the GM cars I've tuned, including my Nova so I'll have to look see what cold starts look like on those.

I did check the IAT value and it says 50F. Same with coolant temp.
I'll bring a known good IAC in tomorrow and try that.

I will also do a write entire, it never hurts.

Thanks

2xLS1

iTrader: (25)

It can.

RonSSNova

iTrader: (3)

it didnt

2xLS1

iTrader: (25)

Bet it didn't fix the problem either.

RonSSNova

iTrader: (3)

Ha. No it didn't. :-)
It's a bit difficult as you only get a few tries at cold start.
Looking at cold start logs for my Nova, IAC is at 200 when I start it. Same temp conditions.
So either I have a goof in this tune, or the IAC is sticky.

RonSSNova

iTrader: (3)

Batt had died. And as I Remember, these things tend to lose their idle brains when the batt is disconnected.

it also appears that this aftermarket FB lacks enough IAC area as it wants more air at cold idle than 310 counts can deliver at the cold idle speed I selected.

ill fudge it around a bit with the throttle screw.