My stepper motor is...........not there.

[Bish400]

So after trawling through Pistonheads for hours I was fairly sure I had a problem with my stepper motor.
The car is in storage and I've not had her long.
Got her out this evening to clean out the stepper motor only to find well... NOTHING! no stepper.
It starts from cold first turn of the key but idles very low and lumpy for a few while, not even high enough to turn the battery warning light off. If I blip the throttle she revs then won't idle stalls. Wait a few minutes and she'll start again.
When hot and coming off the throttle say at traffic lights sometimes it will stall also.
So I'm thinking I need to manually bring the idle up to solve these issues.

Second Problem is that every now and again when she's warm i.e sat in traffic I get miss fires, back fires, very little throttle response and struggles to rev over 2500 rpm or idle. I have a battery isolator (Yes I know that's not great) so i switch that off and on and she comes back to life.
For this I was thinking MAF?
I've downloaded RS-RV8 on a tablet so will plug in the rover gauge tomorrow.

other than what I've described and the odd bit of shunting the car drives like a dream.

[Steve_D]

So if it's not there then what is in its place?

Steve

[Bish400]

A plate covers the hole.

[ITVRI]

If you are running the original 14CUX I think you will need to fix the bodge job and reinstall the stepper first to get your proper idle back and then start investigating other problems. The second problem you describe could also be linked to the missing stepper or fault code caused by it missing as turning the battery off and on will clear a ECU fault for a short time.

Edited by ITVRI on Sunday 6th December 06:52

[blitzracing]

As the man says you need the stepper put back. Peaple also put restrictors to limit the airflow because the idle is high, but you need to put it all back and see if this is the case. There are lots of reasons for am erratic idle but RoverGauge will show you what's going on. I saw a plumbers gate valve on one car used to control the idle! There is a base idle setting on the top of the plenum that should be basically set just to allow the engine to just tick over when warm, ( say 600 rpm) and the stepper should allow enough extra air to reach around 800 rpm. The values do vary depending on the settings in the fuel map, but above as rule of thumb is ok.

[blitzracing]

Base idle is covered here: http://www.g33.co.uk/pages/technical-fuel-injectio...

[Bish400]

Thanks for your replies. I've ordered an oe stepper motor as in a box that came with the car i found this.



Plugged in the rover gauge and initially got no faults but after a few minutes on tick over i got.





Eventually i got the stepper fault which is now constant with the other 2.
Fuel map 5 stayed throughout.
I didn't get any spluttering even when it was hot.
Lt odd/even didn't read at any point?

Edited by Bish400 on Sunday 6th December 17:21

Edited by Bish400 on Sunday 6th December 17:22

[blitzracing]

The AFM and throttle pot error tie in together, basically it occurs when the output of one does not match the output of the other, ie, you cant have full airflow with a shut throttle. Most likely cause is a break in the carbon track in the throttle pot so it drops to zero output at some point in the throttle movement. This also causes the fuel to be restricted. Throttle pot faults may show up if you look at the throttle pot movement in RoverGauge from shut to fully open, but the fault may only happen when things get hot. As for the lambda- something is very wrong here- this situation cant exist. Even with dead lambda probes you get a fuel trim value, so you need to use a test meter on the black and white output wires (white is ground) and look for the signal in the 1 to 2v range to see whats going on. I cant say if the Android version of RG is bug fee as I dont use it. If its not a bug, id suspect something fried in the ECU.

[Bish400]

blitzracing said:

The AFM and throttle pot error tie in together, basically it occurs when the output of one does not match the output of the other, ie, you cant have full airflow with a shut throttle. Most likely cause is a break in the carbon track in the throttle pot so it drops to zero output at some point in the throttle movement. This also causes the fuel to be restricted. Throttle pot faults may show up if you look at the throttle pot movement in RoverGauge from shut to fully open, but the fault may only happen when things get hot. As for the lambda- something is very wrong here- this situation cant exist. Even with dead lambda probes you get a fuel trim value, so you need to use a test meter on the black and white output wires (white is ground) and look for the signal in the 1 to 2v range to see whats going on. I cant say if the Android version of RG is bug fee as I dont use it. If its not a bug, id suspect something fried in the ECU.

Thanks for you help on this, what I think I'll do is wait for the stepper motor to turn up, fit that and make sure its working correctly before I go any further.
I tried a different android this morning and the same lambda readings came up i.e initially no readings at all and after a few minutes I got the st odd and even reading only. I will set up the laptop version before I test again.
The MAF and Throttle both seem to follow but the fault code comes up straight away.

[blitzracing]

You need to clear the fault code then and see if it reoccurs. I don't think the ECU can recognise that specific fault on just power up, just the throttle pot test on its own by the small voltage the throttle pot gives when closed. Its worth plugging the old stepper you have in, and try some steps on it with RoverGauge and see if it moves. +/-30 is a good number. If you need to get the unit apart apply over 180 steps until it winds out fully, then you can clean all the parts. Be careful to put the motor in a bowl when you do as its all sprung loaded and pings apart.

[Bish400]

Just plugged in the lap top version and had the same Lambda problems so there's more than likely a problem but I don't have time to look anymore this week. Also kept an eye on the throttle abs % and every now and again it went to zero from 7. Gives me some places to go next week.

[blitzracing]

Both long and short term trim will start at zero after an ecu reset, but they should start to move even with no lambda voltage as long as you have a warm engine. It can take quite a few minutes of driving to throw a lambda probe error, even though it takes only around 25 seconds for the probe to start working. If the ECU has been reset, and the engine only run a short time it may account for the zero trim.

[Bish400]

Should have mentioned that this was on a 45 minute drive so from what i saw the throttle has an intermittent fault where it drops to zero.
The long terms never registered at all.

[blitzracing]

The way it works is, the short term trim should start to cycle depending on the probe output. The short term trim is not the actual probe out put, but the ECUs response to try and get the probe to switch. So if the probe out put is 0 volts, the ECU will remove short term fuel trim to add more fuel - so you should get lots of "adding fuel". If the probe still wont switch the ECU moves the long term bit by bit, adding more and more fuel, until it sees an output of about 1.2 volts from the probe. Once at this point the short term should be able to cycle around the mid point adding and removing fuel constantly to keep the probe switching between 0 volts ( lean) and about 1.4 volts (rich). This only happens on a hot engine at idle, and takes about 2.5 mins. Dont touch the throttle at this point or it stops the long term moving. The long term trim should then stay fixed at whatever, until the next idle session where it may move again if anything has altered. A good long term trim is about 30% or less, but as long as its less than 100% the ECU is coping. If the ECU reaches 100% long term, it should throw an lambda error as the probe has not responded. The ECU trim is held in battery backed up memory in the ECU, so any interruptions in power (like isolation switches) will kick everything back to 0 %. As you can see your scenario does not fit what's meant to happen so you will need to get the test meter out to look at probe voltages or possibly borrow another ECU to try.

[Bish400]

With the idle problems i already have, i.e no stepper fitted and throttle pot dropping out intermittently I think I'll fix both of these before i move on to this. The parts should all be here for the weekend so I'll get them on and reset all the faults. I have the laptop and app versions now so can cross reference both. Again thanks for your help on this, slowly getting to the bottom of things.

[Bish400]

Finally got around to fitting the new stepper(and pipework) and new throttle pot and the car is starting and driving much better. Cleared all the ecu faults and I'm left with one.
MAF fault, intermittent. Only happened once today. Car drove fine but struggled to idle. Switched off engine and restarted. Problem gone.
Will look at this later in the week and check the voltages

[Belle427]

Check the connector to it, they are a common issue.

[Bish400]

blitzracing said:

The way it works is, the short term trim should start to cycle depending on the probe output. The short term trim is not the actual probe out put, but the ECUs response to try and get the probe to switch. So if the probe out put is 0 volts, the ECU will remove short term fuel trim to add more fuel - so you should get lots of "adding fuel". If the probe still wont switch the ECU moves the long term bit by bit, adding more and more fuel, until it sees an output of about 1.2 volts from the probe. Once at this point the short term should be able to cycle around the mid point adding and removing fuel constantly to keep the probe switching between 0 volts ( lean) and about 1.4 volts (rich). This only happens on a hot engine at idle, and takes about 2.5 mins. Dont touch the throttle at this point or it stops the long term moving. The long term trim should then stay fixed at whatever, until the next idle session where it may move again if anything has altered. A good long term trim is about 30% or less, but as long as its less than 100% the ECU is coping. If the ECU reaches 100% long term, it should throw an lambda error as the probe has not responded. The ECU trim is held in battery backed up memory in the ECU, so any interruptions in power (like isolation switches) will kick everything back to 0 %. As you can see your scenario does not fit what's meant to happen so you will need to get the test meter out to look at probe voltages or possibly borrow another ECU to try.

I have a Range Rover ECU on the way from the same year - 3.9 litre, I believe the chip will need swapping over from my existing ecu if it does turn out to be the ECU that's the problem?
Will check the voltages first.

[Bish400]

Belle427 said:

Check the connector to it, they are a common issue.

Next on my list of things to do thanks

[Steve_D]

There are upgraded chips readily available from guys on here. I had an ECU issue which turned out to be the TVR chip and problem solved with the replacement chip.

Steve