Idle speed

garkahn90 · 11-05-2006, 08:06 PM

This is my first time to this section of the forum. The tuning thing sound like a lot of fun. I've read the introduction and now I have some questions.
Looks like there is some investment required. As an alternative are there people out there that make changes for others, or for a fee? Or sell reprogrammed Eproms?
My car is a '90 and completely stock as far as the engine goes. I am going to upgrade my exhaust to an LT1 exhaust and considering 1.6 roller rockers and maybe some porting and polishing. Of course that could change. But with these few changes I don't think any reprogramming would be required. But there are some characterstic that I would like to change. Idle speed is one. Right now my engine idles kind of high, 900 - 1000. I've done all the maintenance so I don't think its anything other than what is programmed in the ECM. One of the other things also has to do with idle speed. I understand that when the car is moving and you let off the throttle the idle speed does not drop to the mininum, for emission purposes. Are these things that can be altered with re-programming?

Thanks

Vis Croceus · 11-05-2006, 09:50 PM

Quote:

Originally Posted by garkahn90

Right now my engine idles kind of high, 900 - 1000. I've done all the maintenance so I don't think its anything other than what is programmed in the ECM.

You stock engine was not programmed to idle at 900-1000. You have mechanical problems.

Quote:

As an alternative are there people out there that make changes for others, or for a fee? Or sell reprogrammed Eproms?

That's odd that we don't have tuner info in the FAQ...

Yes there are many people who can tune these things. A search in this section or C4tech for "tuner" or "tuning" should turn up some names and reviews.

garkahn90 · 11-06-2006, 06:22 AM

Ok, well let me put the question another way. Can the ECM/ Eprom be reprogrammed to a different idle RPM? Can other Engine speed control characteristics be reprogrammed?

SunCr · 11-07-2006, 03:25 PM

Yes, Base Idle can be programmed to another number. Stock is spec'd at 100 +/- Actual RPMS from Target in Park/Neutral; 50+/- RPMS in Drive.

Before you do anything, hookup a scanner to record Actual vs. Target RPM and note the Coolant Temp Signal. Post those numbers for further help. Changing anything when there's an issue creates more issues.

Sam Lam · 11-08-2006, 02:07 AM

garkahn90: I have to agree with the previous posts in that your car is not programmed to idle at 900 - 1000 RPM. Here are the programmed values for idle for my 89 model Vette and these are stock:

Idle RPM vs. Coolant Temperature

Deg F RPM

306 575.00
284 575.00
262 575.00
241 575.00
219 575.00
198 575.00
176 575.00
154 600.00
133 600.00
111 750.00
90 900.00
68 950.00
46 1050.00
24 1050.00
03 1050.00
-18 1050.00
-40 1050.00

I have a Moates adaptor and now have the idle to be at 700 RPM when the coolant reaches 178 deg F. Before you do the ECM change, you should fix the mechanical or vac problem you currently have.