reset ignition timing after setting BISS & IAC?

[1Gina2G]

I understand from what I've read that if you find yourself replacing the IAC you should reset the ECU by disconnecting the battery then reconnecting, (after the install) then with the IAC unplugged, set the BISS to the correct position with the engine warm. I had suspected the IAC was causing me to stall upon slowing down in neutral but the IAC still has perfect resistance still and since I have the battery disconnected now the ECU is going to be reset so I was wondering when I reset the IAC then the BISS should I just go ahead and reset ignition timing or is it not necessary? I set it to 5* with the engine warm and timing connector grounded recently within a month. I should at least recheck right?

 

[1Gina2G]

Does anyone have the slightest clue? Does reseting the BISS have anything at all to do with ignition timing?

 

[clipto]

Nope.

 

[steve]

On your 95 how are you setting the base timing? It's fixed unless you have a different engine or head installed.

On cars where the base timing is adjustable, the base timing should be set before setting the BISS. But if the idle speed is so far off that you can't set the timing (above 1200 RPM) then you might have to set the timing, adjust the BISS, reset the timing, and then reset the BISS to get things adjusted correctly.

Disconnecting the ECU clears a bunch of learned parameters including the ISC/IAC positions so it's a good idea if you have a bad ISC to reset the ECU so it learns the correct setting rather than slowly migrate from the old settings.

 

[1Gina2G]

On your 95 how are you setting the base timing? It's fixed unless you have a different engine or head installed.

On cars where the base timing is adjustable, the base timing should be set before setting the BISS. But if the idle speed is so far off that you can't set the timing (above 1200 RPM) then you might have to set the timing, adjust the BISS, reset the timing, and then reset the BISS to get things adjusted correctly.

Disconnecting the ECU clears a bunch of learned parameters including the ISC/IAC positions so it's a good idea if you have a bad ISC to reset the ECU so it learns the correct setting rather than slowly migrate from the old settings.

Thanks for finding my thread!

To clarify- 95 body with eprom ecu, 6 bolt block with a 7 bolt head. Would it still be fixed? If not is it still be set to 5* with the connector grounded and then 7 with it ungrounded?

 

[Rock2610d]

I tend to preach this but I learned from experience....

Set the throttle, accelerator,and throttle body cables to spec. If you do not know the spec they are probably wrong.

FYI....Throttle body cable needs to be set with IAC ON, engine off, accessories off. IE the ignition key in the on position. Once that is done give it about 1 mm slack.

 

[redbud23]

Rock2610d that is pretty much the same method In use.

 

[steve]

I set it to 5* with the engine warm and timing connector grounded recently within a month.

To clarify- 95 body with eprom ecu, 6 bolt block with a 7 bolt head. Would it still be fixed? If not is it still be set to 5* with the connector grounded and then 7 with it ungrounded?

How did you check it and set it before? If you have 6 bolt block with a 7 bolt head I assume you have some sort of CAS for your timing signals. If it's adjustable then you need to set it to 5* BTDC with the ECU informed that you're setting it. (grounding the connector or telling DSMLink)

 

[1Gina2G]

How did you check it and set it before? If you have 6 bolt block with a 7 bolt head I assume you have some sort of CAS for your timing signals. If it's adjustable then you need to set it to 5* BTDC with the ECU informed that you're setting it. (grounding the connector or telling DSMLink)

I set it basically how i was asking- but with the engine warmed up , i will ground the connector then hook up the gun to number 1 and set to 5 on the cover. I remember the engine changing howit sounds while idling slightly, which after disconnecting the connector i remember seeing 7, could it ever be anything else after setting to 5? Would it ever be at 5 for example, after setting & ungrounding?

Also, shouldn't the ignition timing stay set as long as the CAS is tight, even if the ecu is reset?

All this started on suspicion of a bad IAC which i confirmed is still perfect. So since the ecu has been reset after checking the IAC (had to take the battery out for room) i should recheck / set base timing and only touch the biss if the idles off at this point right? Which should/ could only happen if base timing is not 5* with it grounded and 7* ungrounded right?

Thanks for all the valueable information!

 

[steve]

shouldn't the ignition timing stay set as long as the CAS is tight, even if the ecu is reset?

Correct. It's a physical adjustment to sync the CAS signals to the ECU Reference.
As long as the timing belt doesn't stretch or you have adjustable cam gears that get moved it should remain the same once set.

All this started on suspicion of a bad IAC which i confirmed is still perfect. So since the ecu has been reset after checking the IAC (had to take the battery out for room) i should recheck / set base timing and only touch the biss if the idles off at this point right? Which should/ could only happen if base timing is not 5* with it grounded and 7* ungrounded right?

Thanks for all the valueable information!

Checking the ISC/IAC coil resistance doesn't mean it works. Did you pull it out and verify that the steps all the way out and back in when you turn the ECU on?

Are you using a 2G TPS and is it set correctly (IPS switching point)?

The timing at idle with the timing check connector ungrounded depends on things like air temp, coolant temp, altitude, RPM, engine load. If it reads 5* BTDC with only timing check connector grounded the CAS adjustment sound good.

 

[1Gina2G]

Correct. It's a physical adjustment to sync the CAS signals to the ECU Reference.
As long as the timing belt doesn't stretch or you have adjustable cam gears that get moved it should remain the same once set.

so does the BISS have to be adjusted if the IAC is bad or comes out for inspection? if so you would do this after checking ignition timing with the light right?
so if so I would ground timing, check / adjust timing saying the IAC is bad. I'd think you would have the IAC plugged in while checking timing correct? then unplug it and adjust BISS...unless idle is already good or close enough?

Checking the ISC/IAC coil resistance doesn't mean it works. Did you pull it out and verify that the steps all the way out and back in when you turn the ECU on?

I only checked resistance, I'll pull it out tomorrow afternoon and check.

Are you using a 2G TPS and is it set correctly (IPS switching point)?

the TPS is a 2G, all 2G TB that's rebuilt for the matter, voltage and percentage has been adjusted along with the right slack in the gas peddle. and right now I only have evoscan on an eprom ecu so I can only log, but the percentage and voltage have perfect readings all the way up and pedal to the floor. evoscan also shows ISC postion go from 0 to 1 as soon as you touch the pedal.

 

[steve]

so does the BISS have to be adjusted if the IAC is bad or comes out for inspection?

if so you would do this after checking ignition timing with the light right?

so if so I would ground timing, check / adjust timing saying the IAC is bad.

I'd think you would have the IAC plugged in while checking timing correct? then unplug it and adjust BISS, unless idle is already good or close enough?

I only checked resistance, I'll pull it out tomorrow afternoon and check.

The TPS is a 2G, all 2G TB that's rebuilt for the matter, voltage and percentage has been adjusted along with the right slack in the gas peddle.

Right now I only have evoscan on an eprom ecu so I can only log, but the percentage and voltage have perfect readings all the way up and pedal to the floor. evoscan also shows ISC postion go from 0 to 1 as soon as you touch the pedal.

If the ISC is bad you have to adjust the BISS when you replace it. Just pulling it out and reinstalling it shouldn't make a difference.

Why would you unplug the ISC? It needs to be connected while your adjusting the BISS. If evoscan doesn't have an option to turn on the adjust BISS mode then adjust it by the ISC steps at idle to about 30.

As long as the IPS (not ISC) changes when you put the feeler gauge in between the stop screw and the pulley per the FSM it's right.

So you would start the car and let everything come up to temp, make sure the wheels are straight and the radio, blower motor, etc are off. Idle speed needs to be 750 +- 50 RPM. Stop the engine, ground the timing connector, hook up the timing light and start the engine to verify the base timing is 5* BTDC. If you have to adjust the CAS then you may have to adjust the BISS after. Remove the check timing connector and the timing should advance. How much depends on where you are.