I was directed here from the TBI board. I am wanting to get my TBI motor to where it doesnt idle around 1500 rpms for a long period of time while its cold.. i was told this was controlled by the ECM.. what would i do to the chip to eliminate this?

 

you could try a search, that may lead you to the answer faster. I recommend you read and understand the excellent paper pertaining to IAC Control here that will answer your question -- and should give you some ideas of what else is possible.

 

There are a couple of methods of reducing the cold max RPM limit. Are you setup to data log and burn chips?

Another item to consider is that the the cold max RPM is lower when the trans is placed into drive. This in effect will lower the RPM.

RBob.

 

what i really dont like about that idea, is the fact of putting it in gear at 1500 rpm's cant be good on the drivetrain overtime

 

ok i went to the website that was recommended and found this:

To reduce flair-up on engine start:

Lower the park position @ 0x5C2.
Lower the park to run delay @ 0x5C3.
Lower the kickdown time delay @ 0x5D7.
Lower the coolant vs. position values @ 0x5F5

I think this is what im looking for.. not sure. anyone know if this is what eliminates high idle on cold starts?

 

Not the correct parameters. If you aren't set up to burn PROMS then you can open the Park/Neutral wire at the shifter (orange w/black stripe). This will tell the ECM that the car is always in drive.

RBob.

 

so it will no longer flair up on cold starts if i unplug that wire? the owner before me put in a B&M console shifter... where does this wire run too?

 

A startup flair is different then what you are asking about. The flair at startup is just that, as the engine catches and the RPM's increase , they flair to a high speed, then come down.

This startup flair can be as high as 1,800 - 1,900 RPM.

My understanding is you are asking about the idle just sitting high until the engine warms up. This is different and is controlled by different parameters.

The wire in question runs from the shifter to the ECM. It is pin B10 on the ECM. When in park or neutral the shifter mechanism just grounds the wire.

RBob.

 

Biggest help is to dump alot of steps from the 'cold' portion of the IAC steps vs. cool temp table to get the idle down to where you want it on the first few minuts of initial startup. They add ALOT of steps when cold, basically they max the IAC steps out to the most allowed. It was so many that it was a safety issue. When it was wet out my car would go straight down the driveway with the front wheels locked up. Thats how hard it pushed in drive when cold.

Of course, you need to be able to burn proms to cure this.

 

yeah thats what sucks.. i cant burn proms you think the unplugging of that wire would help?

 

Id pull it. That way your car wont idle as high in neutral. On my ecm, though, I dont have that option. Jsut limits it to 1400 rpm when cold.