Cold start idle help

[oztracktuning]

Since fitting the BBK TB i have had great gains in power BUT its changed the cold idle behviour dramatically what worked before doesnt work anymore.

What can i do to dial this in accurately again. It is simply starting and stalling - i need to push the throttle and keep the revs up well above 1200rpm or it will stall. After 30s or so it is OK.

If i check the AFRs what should i be aiming for at idle. I am not sure if the car has too much idle air or doesnt have enough??

Have been stuffing around for a few cold starts now trying to get it right.

The PLX wideband takes time to calibrate and settle - this is masking the ability to get accurate afrs. But i can plug it into an external power source and have it ready before the car is started. If this is the way to go.

[ringram]

Hey dude, check out the "idle transition sticky" you will want to log RAFIG which is a calc pid and RAFPN they show you what air the car is trying to add to get the car to your required idle speed. If you then add that to your desired air table things start working well again.
What was your old idle speed? You might be getting too much air with the larger tb making it lean, opening tps adds fuel.
Check out that sticky anyway it helped me.
.. sounds like I might want a 80mm bbk myself :)

Ok, so its no longer sticky.. try here instead http://efiforum.iqd.co.nz/showthread.php?t=149

[Tordne]

Also once you achieve normal temp check what the IAC Steps sits at when at idle. Mine sits at around the 60 mark at warm idle.

I'd say if the car is stalling you don't have enough air.

Did you change the IAC Effectice Area table at all? From what I've been reading most recently it is not required. I have had best results with a stock table.

As Richard says, log the RAFIG from cold through to warm and apply to the Desired Airflow table.

I'd also be inclined to disable idle learning, set B4501 to max setting (140*C). At least while tuning the idle.

[oztracktuning]

Thanks guys
All set to do the logging and some changes tommorrow.

[Doc]

I have a 80mm BBK. Ditto on the RAFIG / RAFPN from cold start. Sounds like not enough desair + TB set screw to get IAC to ~60 PN ~100 IG.:)

[The Alchemist]

Hi there from New Zealand.
I've just solved this issue this week for a customer of mine. As an after market tuner you often inherit a job after the mods are all done and as such don't always know the exact details, brands and in the and outs of the components used. Theirin can lie the problem....

After hours of wracking ones brain cells using EFILIVE and altering every possible idle paramater it became very apparent to me that the problem was a physical one not a programming one. The car would surge when cold from 200 rpm to 900rpm and stall at intersections until it warmed up to 60 degree C.
Hot idle and startup where fine.
I removed the idle actuator for a look see to check that it was moving correctly using EFILIVE Scantool to activate the stepper motor during idle control. It seemed to be working fine but as I was re fitting it I noticed that the idle bypass drilling into the manifold side was very small, 5 mm in fact and yet the intake from the Atmo side was approx 12mm in diameter.

mmmmmmmmmm I thought. Obviously the engine simply wasn't getting enough air on cold start and idle up. To prove this I set the throttle stop so the stepper motor was on ZERO steps and the car idled at 900rpm and sent the customer on his way to report back in the morning...
Next morning I got the phone call at 8am, I had barely walked in the front door, " A PERFECT START THIS MORNING! " he said.
Back into work he came and we drilled out the bypass to 12mm, the same as the inlet, and reset the TB stop so the stepper motor had 30 steps or so and tried it again in the morning.
Perfect cold start again... GREAT!
This solved the cold start problem but introduced several other idle issues often discussed elsewhere in these forums. These were easily tuned out with the EFILIVE software after a few trial and errors leaving the car idling like a stocker under all conditions.
Caused a few grey hairs though :)

Mike

[Tordne]

Hey, another Kiwi. Cool :cheers:

[oztracktuning]

It seems to be getting better - will find out tommorrow when really cold again. What i did today after a disaster this morning was set the settings back to the way they were when idling good just before i put on the TB and then i added 13.77% to all the readings in B4403 and things seem to be alot better. Maybe its not the way - i read about this simple solution in another (competitors) forum !

[ringram]

Yeah they are good for hack jobs. Read the real way to do it here :)

Mine was a case of too much air. I had so much air initially that spark was down to 9 deg to slow the mother down. Of course it was shuddering like crazy. Slight throttle caused it to stall due to crap spark timing. Anyway it was fun to sort it out.

I think I need a massive cam to tune now. Tordne get a TRex, it will be more fun!

[Tordne]

Nah I think mind mind is made up on a FM13 on a 112+2. That will be enough fun :)

[ringram]

Now Ive got/had a small 220 cam, Id agree with you. Mind you the flat power band is nice. Good for off idle driving.

[oztracktuning]

Mine is now starting well at above 50 deg ECT but cooler started with no throttle it fires and stalls for the first 30s or so. Then its fine.

Here is the log of this mornings drive - i would appreciate anyone having a look at it and making suggestions for pids to log - as it seems the pcm doesnt like some of the choices here as well.

www.oztrack.com/clubsport/hometoghscooler.zip (http://www.oztrack.com/clubsport/hometoghscooler.zip)