Commander 950 idle issues

[ks71z28]

On ocassion my Idle will raise from the 850 setting, to about 1400 rpm. It will stay that way until I shut off the engine and restart it. I was doing a cruise night and doing a lot of stop and go, and idling in 1st gear. The car was idling at 1000 rpm all night. If I put the clutch in when idling in 1st gear, the idle would rais to 1400 or so then settle back to 1000 rpm. I hooked up the lap top and check the idle, the cell value was 850 rpm, and the car was staying at 1000 rpm, with a hint of a surge. When changing the cell values, there was no change in RPM. I checked the parked value of the TPS and it was fine, as well as through to WOT. Is there possibly somithing going on with my IAC motor? Could this be a vacuum leak issue? Just a bit of trouble shooting advice

Keith

[camcojb]

I would post your question here; the moderator is a Holley EFI engineer, and tons of the Commander 950 guys hang out there.

http://www.chevytalk.org/fusionbb/showforum.php?fid/35/keyword/Fuel_Injection/

Jody

[DeltaT]

First I would open the 950 software, then go to 'About', click on 'Version' and make sure that the 'Advanced User' box is selected. This enables you to see a few more variables that are important to your problem. I would try playing with the 'Proportional' value in the "HW Settings', 'Idle Air Control' window. Try lowering it to 50, and see if that fixes your problem. If it doesn't put it back to where it was and try the next - you can always fine tune it later.

After trying the above, then it sounds like the known noise issue with the IAC could be affecting you. There's an embedded workaround in the unit, if you are running a later version:

Make sure under IDLE AIR CONTROL that you have the MINIMUM IAC POSITION SET TO 0 for the idle area. IE, if your idle TPS is 36, make sure the first 4 boxes (from the left) are set to 0. This enables the fix in the firmware. Any other value other than 0 won't enable it.

Go and drive and see if that fixes your problem.

This enables some 'filtering' logic that can help deal with noise generated by the WBO2 controller that confuses the IAC motor and allows it to get out of position.

Other things that may help: Separate ground for the WBO2 controller; ensure your 950 Case has a good connection to ground; try to route the IAC wires away from high voltage wires.

Like Jody says, come on over to Chevytalk 'EFI/Fuel Injection and Engine Control Systems'. It's a large 950 and other EFI community.

Jim

[ks71z28]

After some diagnosis, I know the idle air motor is working to some extent. When I plug the hole in the TB, I can watch the sensor on the monitor try and open. The car also idles smoother with the idle air hole pluged off, but at a low RPM ofcourse. I also noticed that the car when started (hot) it idles sometimes much higher than normal, and this amount varies from time to time. Shutting it off and restarting usually brings idle back to normal, but the surging from 800-1000rpm is still there. Is it possible for IAC to be sticky when it is faulty? Jim I will try you suggestions today. By the way another Nor Cal event is on its way soon!

Keith

[DeltaT]

Hi Keith,

It is possible to have a sticky IAC, but your problem has been seen by a number of people, to the point that Holley did this workaround.

I just sent you a PM.

Jim

[Chad-1stGen]

This is a known issue and the workaround may cure it or help it.

The C950 system really falls on it's face when idle is concerned. I get mine set up perfectly and 200 miles later it idles down way to low idles up to high.

I don't profess to be an EFI expert but tuning a reliable idle shouldn't be this hard.

[ks71z28]

So what is the issue? My Idle is set at 750 rpm, actual idle is about 900 +/- 50 rpm. The IAC is not bottomed out (value 15-30). I have had the EFI on the car for 3 years, and upgraded the Firmware and Went to PRO and WB o2 1.5 years ago, just recently i have started having this issue. I checked for leaks at a shop using propane, and checked everything. I moved the o2 ground separate from the ECU, like Holly said. I set the minimum IAC vaue to (0) in the 1st 3 boxes, nothing has changed. Holled did mention that I should be getting no less than 11 volts at the Injector red wired at cranking, my car is seeing 10 volts. They said it may cause the IAC to not set up properly, but I'm pretty sure the IAC sets itself when the key is turned prior to cranking. The car still surges and idle varies EVERY time the car is started, 950 once, 850 later, and needle has slight bounce on tach, hell a carb can idle smoother than that, and the EFI was better. I'm kinda bumed out, sorry for the ranting guys

Keith

[camcojb]

this may not have anything to do with this issue, but for those who can't get the idle as low as you want, did you set your throttle blade opening?

On any new EFI install I get the car up and running, fully warmed. Shut off all idle timing compensation (so the timing won't try to control idle speed), then command a very low idle speed. This should close the IAC completely trying to reach this speed. Then set your idle speed manually with the throttle blade screw for the lowest idle you'll ever see in normal use. Reset the TPS, and then add the timing control and correct idle speed back into the computer.

This lets the throttle blade control your correct minimum idle speed and gives you full IAC and timing range to compensate for loads like turning the wheel with ps, a/c, electric fan kicking on, etc.

If the throttle blade is too far open the IAC and/or timing comp may struggle to get the idle low enough, plus you've used up a bunch of their range trying to get the proper idle speed.

Jody

[andy2175m4]

A couple of suggestions:

1. go back to your last good working fuel map/file and reload the file completely. I find that works. the IAC settings can be very mysterious. Do you have a laptop ? Hook it to the ECUm put in on the front seat, go for a cruise, and when the idle starts to misbehave, look at the IAC setting right away to see if it's goingh high and low on it's own. I have seen this. The only cure was to reload the entire ECU program.

2. Vacuum leak? this is a real possiblility. get 8 ft of 1/4" hose, and put the vacuum gage on the front seat. Watch the gage as you drive, ...if you see it do something not coordinated wit your gas pedal, you probably have a intermittant manifold leak. A vacuum leak cannot be found without the gage.

[steinepstein]

I am putting together a similar combo but I am running a Motec M48 with the 950 commander manifold and the idle control is done much differently. We actually welded up the triangular looking hole on top of the throttle body and then welded a bung on the side of the throttle body where the current IAC goes. Instead we use a Ford IAC that will mount on the firewall. I was told the IAC/Motec setup is a little older from the design perspective (since the Motec M48 was originally built in '94) but works great. I can try to get you a picture if you like.

JE

[ks71z28]

the issue was fixed after holley gave me a slew of try this or try that. It then was well send in your ECU and we will update your firmware. This has been an issue and they knew it from the start, so they suck! But it was fixed and all is better

Keith