I've been searching and found nothing.

Before I Replaced the ISC with 2G version, the Idle used fluctuate between 700 and 1500. At first I thought the problem was because I had installed bigger cams. But now, I'm thinking otherwise.

I reset the BISS at 800 (ecu reprogram from Steve) for that target by grounding the ecu and after I ungrounding it, it shoots up to 1500 rpm's when idling.

????????


thnax

Have you tried another TPS?

Also, make sure your throttle cable has a little slack at idle. Even unhook it from your TB to see if it helps.

Make sure your idle switch (closed throttle position sensor) is positioned and functioning properly. You should see it switch on/off on the logger when you actuate the throttle. Can also be tested with a multimeter since it's a simple switch to ground.

Rob, I'm using the MMCD program. Which one is the Idle switch from that program or is it from another program.

I've tried another TPS. But I will try giving a little slack on the cable.

Acccording to the MMCd website, it's called "idle switch".

Thanx Rob,

I check the software and I can't for the life of me find that on the datalogger.

I tried giving it slack and nothing.

The confusing part is that when the ECU is grounded, it idles normally but shoots back up when ungrounded.

It is definitely idling high from a sensor problem.
Grounding basically tells the ECU to ignore the sensors.

Mine does exactly this when the wire falls off of my idle switch, or when it's not adjusted properly.
You should use a multimeter to check it.

Remove the connector, and put one probe on the sensor prong and the other probe on the throttle body (ground).
Check the ohms, it should be zero with the throttle closed and 1 with the throttle open.
The sensor should not hold the throttle open at all, and you should not need to turn the throttle far to see the state change.

If it's not working it could be:
- not screwed in far enough
- screwed in too far
- the pin on the sensor is dirty (clean it with sandpaper)
- the contact point on the linkage is dirty (clean it with sandpaper)
- the throttle body's ground is weak (add a ground strap to the throttle body or below the switch assembly)

Unfortunately, without seeing the sensor on a logger, you won't know for sure if the ECU sees it or not (to verify the wiring end to end).
The next best thing to do is unplug the ECU harness and test as above with the multimeter in the cabin and the connector on the sensor.


Another thing that I just throught of...
Check the speed sensor (reed switch) connection to the ECU at pin 18 - not sure what that is on the logger.
If the ECU thinks you are moving, it'll keep the idle up. It assumes you are coasting and you need the rpm for brakes and accessories.

Is this what you mean? I got a reading of 4.2 ohm's.

I think you're on the 200ohm setting, I should have mentioned to set it to 20K. I do that automatically for this stuff.
That is probably close enough to zero, to indicate that your idle switch is closed (and probably working fine).
Does it go to 1 when you open the throttle?

The problem could still be lingering between the connector and the ECU.

I retried and it is at zero. When I opened the throttle, it went off the chart.

You might be correct. Since last year, I've noticed that when I decelerate, I can see the A/F gauge still oscillating for a few more moments until it drops and sometimes longer.

I know that the pocket logger has the feature to see if the ECU is detecting the Idle switch but I can't find it on the MMCD program. I don't have the Pocket Logger.

That's one of the symptoms for sure.
The switch can be sticky too. Generally, I've found it to be a royal pain in the ass to adjust. It's either pushing the throttle open a touch, or it's making intermittant contact. The sweet spot is narrow.

Do you how to fix this problem Rob? I guess we (YOU) have isolated the main cause of the idle surge.

For me, the problem was the adjustment of the switch.
For you it's a little different (and more difficult to diagnose), since the problem is constant, and the sensor itself seems to work OK at a stop.

You would have to work your way towards the ECU, and hopefully find the problem along the way.
The logger is invaluable here, since you could save yourself the trouble and move on to something else if you observe good signal.

This may help with your logger:
http://www.3si.org/forum/showthread.php?t=203226

Q1 - What do the letters mean in FLAG0 and FLAG2

Flag 02 status bits
A - Air conditioning relay
F - Fuel pump relay
B - Boost related ???

Flag 00 status bits
T - TDC sensor
S - Power Steering Pressure SW
A - AC switch
N - Neutral
I - Idle switch

Another way to check on your logger:
Put the key to ON with the engine stopped, and go through every logger screen while actuating the throttle.
There are only two sensors that should be moving (TPS & idle switch).

Good luck, and may it be the wiring! I'm at a loss otherwise, for now...

If I lived in Ontario, I would definitely take you for beers til you drop.

I tried what you suggested and yes the TPS does registered but the Flag 00 does not. It has S-I but nothing is happening.

Excellent!
Hopefully that logger value is true and you've found the problem, so now you only have to fix some wiring

I check the wires on the ECU and it looks fine. I took out the wire and cleaned it and put it back. While the ECU was out the car idled near perfect. But when I thought everything was ok, I put the ECU back and now the problem persists. This car hates me.

Note, the Idle switch on the logger seems to turn on and off by itself. While driving, the "I" (for Idle switch) blinks on and off. Is this normal or is it suppose to be off when you throttle and on when you let off the gas? Either way, I'm thinking maybe the ECU.

This car hates me for not driving it often.

Depending on the ECU, I've seen it either ON or OFF when the throttle is completely closed. The state will change when you press the throttle, and remain until you let off fully.

It should never flash, unless you're moving the throttle right at the closed point.

Maybe your harness is broken on that pin, or ECU, or the wire is cut in the bundle.

Or, you now have made a good connection on the wire but you still need to adjust the sensor.
There's a jam nut that you loosen, and that will allow you to turn the sensor in and out.
I back it off to make sure it's not holding the throttle open at all, then I turn it in just until it moves the throttle, then I back it off a touch (close throttle again) and tighten the jam nut. This may take a few tries before you get it perfect. Good luck!

Another quick question.

I tried starting the car after a half hour and car started really lean from the A/F and car wanted to stall. Is this related to Idle switch?

problem after problem. What next?

Btw. I'm not sure as to what said about adjusting the Idle Switch.

I bet your fuel trim (low) was affected by the idle switch problem. You should reset the ECU (pull the MPI fuse for a minute).

Have a look at the switch and see how it interacts with the throttle linkage, then what I said should become more clear.

The key is to have the sensor in just enough to register on the logger. If you go too far, then when you tighten the jam nut it will go even further, opening the throttle and causing idle surge.
The sensor looks sort of like a spark plug with a nut on the threads, that nut is what locks it in place - turn it counter clockwise and the sensor will be free.