idle surge with new ISC

[GsxEcutioner]

So, before I replaced the ecu and rewiring the fuel pump, I had a normal running car, I replaced the ISC with a new unit since the old one burned out my old ecu, I replaced the ecu and added link lite and rewired the pump and got P0042 and had to rewire pin 13 to another 12v source in order to get the car to stay running. I now have idle surge and I have not touched anything motor wise except a new isc, I turned the biss all the way closed and still idles between 1000-2100 rpms. It just bounces around, anyone that might know whats up? Thanks
-Shane

 

[diamond-star]

So, before I replaced the ecu and rewiring the fuel pump, I had a normal running car, I replaced the ISC with a new unit since the old one burned out my old ecu, I replaced the ecu and added link lite and rewired the pump and got P0042 and had to rewire pin 13 to another 12v source in order to get the car to stay running. I now have idle surge and I have not touched anything motor wise except a new isc, I turned the biss all the way closed and still idles between 1000-2100 rpms. It just bounces around, anyone that might know whats up? Thanks
-Shane

i believe you have to ground the ecu from under the dash and under the hood..like yor setting the timing.. that will let you adjust your biss. and let you center-out the ISC.
any adjustments with out doing that the ECU will override yours.

 

[GsxEcutioner]

So ground off on link as well as grounding off the timing connector under the hood? Positive on this? I thought link simulated under the hood 0_o.

 

[diamond-star]

So ground off on link as well as grounding off the timing connector under the hood? Positive on this? I thought link simulated under the hood 0_o.

under the dash too...disconect ecm link and ground out under hood and under dash. like ## setting the idle. if this is not done (grounding) it won't let you center the ICM and it will be out of proper range to work well.

 

[steve]

DSMLink has check boxes on the Misc tab to simulate grounding the check timing and diagnostic mode connectors so that you can adjust the timing and BISS.

To set the BISS both need to be checked.

Make sure to loosen the throttle cable before hand to make sure it's not holding the throttle open.
If the FIAV is still active you need to make sure there is coolant reaching it.
The car has to be at operating temp before adjusting the BISS.
Have to pulled the ISC and verified that it steps in and out when you turn the ECU on?

 

[GsxEcutioner]

By grounding on link via the two check boxes i dont need to do this manually correct? I have not checked out the stepper motor but its brand new from a website a few members posted here for me. It never used to do it and the isc is the only thing i changed that would probably affect it, the biss is totally closed but i guess it means nothing if i didnt ground before adjusting?
-shane

 

[steve]

The point of checking it is to see if the whole system, ECU, ECU drivers, wiring, and ISC function before wasting time trying to find other causes. If you had a shorted ISC before it will blow the drivers in the ECU as soon as you turn the ignition on. The drivers can be blown with no visible signs if the ISC wasn't a dead short. It's also common for the ISC traces to be damaged on ECUs. So the quick test is to watch the ECU try to home the ISC when it powers up.

Did you replace the o-ring when you changed the ISC.

This is what a good ISC should do.

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[GsxEcutioner]

I have the new o ring but have not changed it, i will as soon as i get home, if it does move in and out its fine correct? Its a new ecu, i had to change it because it blew the old isc driver, so i see if it moves evrytime the key is put into the ignition?
-shane

 

[steve]

It's not a new ECU only new to you.

 

[diamond-star]

DSMLink has check boxes on the Misc tab to simulate grounding the check timing and diagnostic mode connectors so that you can adjust the timing and BISS.

To set the BISS both need to be checked.

Make sure to loosen the throttle cable before hand to make sure it's not holding the throttle open.
If the FIAV is still active you need to make sure there is coolant reaching it.
The car has to be at operating temp before adjusting the BISS.
Have to pulled the ISC and verified that it steps in and out when you turn the ECU on?

great info man.will save many ppl headaches

 

[snowborder714]

This is what a good ISC should do.

Glad to see you remembered the video

 

[steve]

Glad to see you remembered the video

Glad as hell that you made it. I was wanting to do one for years since it's the only way most people can check that the ISC is working when they have problems.

I've got tools and code I've made to test on the bench so it's easy for me to test and needed since better than half of the ECUs that show up have damage to the ISC circuits. It's not always visible that a driver it blown.

 

[GsxEcutioner]

Ok so My ISC doesnt move at all, neither does the old one that was in my car, During the changed. I switched the ISC, The Pump Rewire, and another ecu with link, those are the only things I changed, So I am going to assume now its the ECU.
-Shane

how do you test the ISC drivers on the ecu?

 

[steve]

how do you test the ISC drivers on the ecu?

If your asking how, you don't.

You can test the wires running from the ECU to the ISC and make sure you are getting 12v on the two center pins but pulling the ISC and checking to see if it moved is about as much as you can check without an oscilloscope, test hardware and software to exercise the drivers.

 

[GsxEcutioner]

What do you mean test hardware and software? And which pins are supposed to have 12v?

Can I just add 12v from another source to these pins?

 

[steve]

Which pins are supposed to have 12v?

Can I just add 12v from another source to these pins?

Like I said, the center pins in each row. They come from the MPI relay and it's unlikely that you don't have power there but important to know for diagnostics.

 

[GsxEcutioner]

All four are supposed to have power ?

 

[GsxEcutioner]

I forgot to mention that the ECU stays solid when I turn the ignition to ACC, but it shuts off only when I turn the car on, whats this mean?

 

[steve]

I forgot to mention that the ECU stays solid when I turn the ignition to ACC, but it shuts off only when I turn the car on, whats this mean?

Don't know what your trying to say.
IIRC the ECU turns on only in RUN and START and stays on until you turn it off. I don't remember it being on in ACC.

 

[GsxEcutioner]

I meant in 2nd click without turning the car on, is the cel supposed to stay solid?

 

[steve]

The you turn the ignition on the CEL should turn on for 5 seconds and then go off.

I'm not running outside to check but I believe the positions on the ignition are, OFF, ACC, RUN, START. On the electrical diagrams IG1 is powered during RUN and START and that's the input to the ECU to turn on the MPI relay and power everything up.

If the CEL stays on you have a fault. If you don't have any error codes being output at the DLC then the ECU is bad.

 

[RedTurboEclipse]

nice video to demonstrate aworking ISC.

ive always just measured resistance between the coils as per the vfaq IIRC,

but wonder why I just didnt pull it out and see if it does what the video does.

Can the ISC still be faulty even though they are measured to be "ok". Current ISC I have I "tested" using the measurement on resistance "should" be good, but I'm having a jumpy idle at times.

I thought it was some misfire, maybe injectors turning off, but I logged on link doesnt show it to be. Idle switch shows to be correct.

I'm narrowing it down to maybe the ISC as well, or because I have a 1G throttle body and the TPS is not calibrated correctly.

 

[steve]

The ISC is part of a system, it can be good and still not work if other parts of the system are bad.
The coils in the ISC are only part of it, and they can be good and it not work for the same reason.

 

[GsxEcutioner]

The you turn the ignition on the CEL should turn on for 5 seconds and then go off.

I'm not running outside to check but I believe the positions on the ignition are, OFF, ACC, RUN, START. On the electrical diagrams IG1 is powered during RUN and START and that's the input to the ECU to turn on the MPI relay and power everything up.

If the CEL stays on you have a fault. If you don't have any error codes being output at the DLC then the ECU is bad.

ok so on Run, it should turn off after 5 secs? because it stays on...........and no CEL at all.
-shane

 

[steve]

ok so on Run, it should turn off after 5 secs? because it stays on...........and no CEL at all.
-shane

I think you mean that the CEL stays on but there is no fault code.

How are you checking for the code?