Throttle status, nothing operate but Open

1 month 3 weeks ago #194351 by okamo11
Hi,

I'd like to know how ECU decide the Throttle status Open or Close.

My Lotus elise have idle error, bit high idle like 1,000 to 1,500rpm.

I checked trouble status by PSCAN but nothing is detected.
Then, I check sensor status and I found strange behavior with Throttle status.
Even nothing operate from pedal, Throttle status shows "open" on PSCAN. It seems "Throttle status open" activate to avoid engine stop.

For example,
just after throttle off, engine speed is down to idle like 800rpm then ECU may recognize throttle open by throttle status "OPEN" even not to operate pedal and idle come to 1,400rpm.

I'd like to know how Throttle status is decided.

I already replace Throttle Position Sensor assembled with Butterfly but nothing is different.

It seems something other reason may have an effect to decide Throttle status.

Need someone's help.


Thanks,

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1 month 3 weeks ago #194353 by NigelOBB

okamo11 wrote: Hi,

I'd like to know how ECU decide the Throttle status Open or Close.

My Lotus elise have idle error, bit high idle like 1,000 to 1,500rpm.

I checked trouble status by PSCAN but nothing is detected.
Then, I check sensor status and I found strange behavior with Throttle status.
Even nothing operate from pedal, Throttle status shows "open" on PSCAN. It seems "Throttle status open" activate to avoid engine stop.

For example,
just after throttle off, engine speed is down to idle like 800rpm then ECU may recognize throttle open by throttle status "OPEN" even not to operate pedal and idle come to 1,400rpm.

I'd like to know how Throttle status is decided.

I already replace Throttle Position Sensor assembled with Butterfly but nothing is different.

It seems something other reason may have an effect to decide Throttle status.

Need someone's help.


Thanks,


It could be the iavc that needs adjusting. Although a TPS reset will settle this, it really needs to be done manually. Marina Brian from the 75 oc. Reset mine using T4, I’d had and ongoing idle issue even though I had tried a TPS reset. When plugged in to T4 the IAVC reading fluctuated between 81 -90 when it should be a steady 21. The procedure is to get an accurate reading the engine temp needs to be precisely 80°c. Once set up, touch wood the car is idling beautifully, it still has an issue with no2 pot not balancing properly, which I hope is down to a dodgy plug or lead. But it’s no longer really noticeable and cold/damp starts are no longer an issue. The throttle response is also 100% better.

I have not yet and I sat yet got PSCAN, but hopefully you should be able to do this using this package. ?


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1 month 3 weeks ago #194354 by Jon-Mini
I know I don't have the same car but the principles are the same.
I had to ensure that the throttle cable was slack when closed. [ on mine the slightest tension caused a rpm rise]
I needed to clean out the iacv unit that had got cruddy / sooty over the years.
These 2 improved my idle to more normal levels.
Hopefully they might for you.

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1 month 3 weeks ago #194356 by okamo11
Hi NigelOBB,

Thank you for replying.
Regarding Lotus Work shop Manual, IACV resetting could be done by operating accel pedal and already tried out. But I haven't care water temp so I 'll try.


I think PSCAN don't have function to reset IACV.

Does someone know how to reset by PSCAN? My car is with MEMS2J.

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1 month 3 weeks ago #194357 by okamo11
Hi Jon-Mini,

Thank you for replying.

Just after replacing Throttle body, I tried without connecting Cable but idle error is remain.

I also already tried to clean up IACV but I'll do it again.

Thank you ,

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1 month 2 weeks ago #194397 by NigelOBB

okamo11 wrote: Hi NigelOBB,

Thank you for replying.
Regarding Lotus Work shop Manual, IACV resetting could be done by operating accel pedal and already tried out. But I haven't care water temp so I 'll try.


I think PSCAN don't have function to reset IACV.

Does someone know how to reset by PSCAN? My car is with MEMS2J.


It’s more setting up than resetting


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1 month 2 weeks ago - 1 month 2 weeks ago #194405 by David Aiketgate
Resetting the iacv (stepper motor) merely tells the ecu that the throttle butterfly is at 3.9% open.(Don't quote me on the actual figure)
If your throttle is actually a way off 3.9% open, the IACV is confused and varies between step settings trying to achieve the correct idle.
Hence the idle rising and falling, or being way too high..

This is complicated because the stepper motor/IACV actually does have stepped settings and the ecu will try to get you to one of the steps. Step 21, I believe.

If your base idle is wrong then this is an endless loop of the ecu using the stepper settings to try to get a set of correct readings.

If you vaguely followed that, what you need to do is get the engine fully up to temperature after a good blast, come home let it idle, but disconnect the IACV plug. Let the idle settle for a few minutes and use torque app or pscan to see what the base idle is. It should be 850-875rpm. (Assuming no other reason ie vac leak, sensor problem.)
If the idle is substantially above or below this then the stepper motor/iacv will constantly hunt or fail to get the idle correct.

You need to adjust the idle set screw on the throttle body.
(I know there are a lot of people who say you must not alter this as it's factory set, but it is adjustable. Its just that the manufacturer didn't want amateurs fiddling with it, hence the non tamper cover that might still be in place) Adjustment may be necessary over time due to wear, or especially if the throttle body has been swapped.

So, reset the base idle to 850 using the set screw on the throttle body, no more than 1/4 turn at a time. After each adjustment wait until the idle settles. Once you've got reasonably close, reconnect the IACV and see what happens for about 5 minutes. If the idle settles to a stable level near 875, great!
If not then you'll need to adjust the idle screw a small amount until you achieve a stable idle somewhere between 850-890rpm. Sometimes you might think you are nearly there and the idle will suddenly change. This is the ecu making the stepper motor move to the next step. Hopefully you will be on step 21 already but if not you'll have to keep adjusting, until you achieve 875 and step 21..

Once you are happy switch off and reset the TPS, if you still have the torque/ pscan connected you'll see the tps sensor change to 3.9% from whatever it was.

I went through all this a couple of years ago and the idle has been rock solid since.

David
:shrug:
The following user(s) said Thank You: talkingcars, Roverlike, Jon-Mini

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