An odd stalling issue....
Discussion
Morning All
Appreciate that stalling issues are quite common on here, however, I have a scenario where I can almost tell how the car will run the moment I turn the key.
For example, on Sunday, started the ignition, and the engine idled at approx 1200 rpm for a few seconds before settling at approx 900. Did approx 20 miles with no issues at all. Idled perfectly when stationary or slowing down.
This morning, although it started OK, the revs were lower right from turning the key, not going above 900 (didn’t get the initial ‘ooomph’ from the engine on start up). Driving to work the engine stalled 4 times when either approaching a junction or when slowing down – couldn’t blip the throttle with one foot on the brake and the other on the clutch. The revs seem to be dipping on slowing down to approx 5-600 rpm - if the revs are 'caught' in enough time, the idle slowly increases again, but if not the engine stalls.
To me, it seems as though something isn’t giving the right ‘reading’ or signal to enable smooth running or idle – but odd that it seems to happen straight from initial start up. Any ideas where to start looking? Is something starting to break down and therefore performing intermittently at present?
And I have checked - the stepper motor is clean!!
Many thanks.
Appreciate that stalling issues are quite common on here, however, I have a scenario where I can almost tell how the car will run the moment I turn the key.
For example, on Sunday, started the ignition, and the engine idled at approx 1200 rpm for a few seconds before settling at approx 900. Did approx 20 miles with no issues at all. Idled perfectly when stationary or slowing down.
This morning, although it started OK, the revs were lower right from turning the key, not going above 900 (didn’t get the initial ‘ooomph’ from the engine on start up). Driving to work the engine stalled 4 times when either approaching a junction or when slowing down – couldn’t blip the throttle with one foot on the brake and the other on the clutch. The revs seem to be dipping on slowing down to approx 5-600 rpm - if the revs are 'caught' in enough time, the idle slowly increases again, but if not the engine stalls.
To me, it seems as though something isn’t giving the right ‘reading’ or signal to enable smooth running or idle – but odd that it seems to happen straight from initial start up. Any ideas where to start looking? Is something starting to break down and therefore performing intermittently at present?
And I have checked - the stepper motor is clean!!
Many thanks.
When you say you've cleaned it, do you mean just the cone end of the stepper plunger or did you carry out the stepper plunger removal process, fully clean and lubricate it ?
Also, they are know to fail so even if clean, they don't step correctly. As (I understand) there is no feedback loop from the stepper to the ECU, the ECU can't tell if the stepper has actually carried out what it asked other than the revs don't respond.
Do you get the buzzing noise from the stepper when you kill the ignition ?
Also, they are know to fail so even if clean, they don't step correctly. As (I understand) there is no feedback loop from the stepper to the ECU, the ECU can't tell if the stepper has actually carried out what it asked other than the revs don't respond.
Do you get the buzzing noise from the stepper when you kill the ignition ?
Mine did this also plus starting dropping a bank randomly. The random cutting out and bad idling was really annoying - the bank dropping only happened a few times and that was the final straw. Took the stepper out and it fell into 2 pieces, so replaced, plus changed the ECU and all now fine. In fact gained 25hp and 25 torque so pretty pleased.
FFG
FFG
How to get it to bits:
1) Get the car warm
2) Remove the stepper from the plenum and reconnect it.
3) Block the hole the stepper has come from with something air tight, or even the palm of a hand.
4) Hold the stepper so you can catch the central cone and spring when it comes out.
5) Get someone to start the car. Without the stepper in place it will rev at around 2k- 2.5k (This is noisy!!), but the ECU will try to slow it down by powering the stepper motor and pushing cone outwards. It will do this in a series of pulses, a few seconds apart, until the cone and spring drop out. (assuming they are not completely stuck). It may take a bit of manual help to get the cone to fully release. Now stop the engine and let it cool.
6) Clean all the muck off the shaft and cone, and lightly lubricate the screw thread inside the motor.
7) To reassemble, wind the shaft back into the motor so far, but align the slot in the shaft with the plastic keyway as best you can by rotating the shaft in its screw thread
8) With the engine cool, then reconnect the stepper motor. Power cycle the ignition on and off, (don't start) and the ECU will try to pull the shaft back in each time the ignition is turned OFF. This is the slightly tricky bit, as if the keyway and shaft are not quite aligned it wont pull home, so you may need a few attempts.
In a few cases cleaning does not resolve idle issues, and this can be due to corrosion in the metal bearing in the rear of the stepper housing becoming mucked up or corroded, and this requires a new unit.
1) Get the car warm
2) Remove the stepper from the plenum and reconnect it.
3) Block the hole the stepper has come from with something air tight, or even the palm of a hand.
4) Hold the stepper so you can catch the central cone and spring when it comes out.
5) Get someone to start the car. Without the stepper in place it will rev at around 2k- 2.5k (This is noisy!!), but the ECU will try to slow it down by powering the stepper motor and pushing cone outwards. It will do this in a series of pulses, a few seconds apart, until the cone and spring drop out. (assuming they are not completely stuck). It may take a bit of manual help to get the cone to fully release. Now stop the engine and let it cool.
6) Clean all the muck off the shaft and cone, and lightly lubricate the screw thread inside the motor.
7) To reassemble, wind the shaft back into the motor so far, but align the slot in the shaft with the plastic keyway as best you can by rotating the shaft in its screw thread
8) With the engine cool, then reconnect the stepper motor. Power cycle the ignition on and off, (don't start) and the ECU will try to pull the shaft back in each time the ignition is turned OFF. This is the slightly tricky bit, as if the keyway and shaft are not quite aligned it wont pull home, so you may need a few attempts.
In a few cases cleaning does not resolve idle issues, and this can be due to corrosion in the metal bearing in the rear of the stepper housing becoming mucked up or corroded, and this requires a new unit.
Thanks for all the replies.
Another eventful drive home. 5 stalling episodes in 18 miles, and all fairly similar - slowing down, revs dropping below 500 rpm - presumably this is too low so the engine dies . Doesnt do much for your confidence with the car.
However, I did lift the bonnet and listen to the stepper when I got home and cut the engine - and to be honest couldnt hear anything at all.
Does this sound suspicious? Is there an eay way to tell whether the stepper is working at all?
Thanks again - in anticipation.......
Another eventful drive home. 5 stalling episodes in 18 miles, and all fairly similar - slowing down, revs dropping below 500 rpm - presumably this is too low so the engine dies . Doesnt do much for your confidence with the car.
However, I did lift the bonnet and listen to the stepper when I got home and cut the engine - and to be honest couldnt hear anything at all.
Does this sound suspicious? Is there an eay way to tell whether the stepper is working at all?
Thanks again - in anticipation.......
Have done that - bonnet up, ignition on then off and yes, the stepper does buzz / click for perhaps a second. So assume thats all ok.
Too dark to check AFM etc - although wires into the top of the plug look OK if a little exposed!
Just loathed to start changing parts randomly unless properly diagnosed......
Too dark to check AFM etc - although wires into the top of the plug look OK if a little exposed!
Just loathed to start changing parts randomly unless properly diagnosed......
The Aardvark said:
Have done that - bonnet up, ignition on then off and yes, the stepper does buzz / click for perhaps a second. So assume thats all ok.
Too dark to check AFM etc - although wires into the top of the plug look OK if a little exposed!
Just loathed to start changing parts randomly unless properly diagnosed......
The buzzing simply means the stepper is getting its pulses from the ECU, it does not mean that the cone is moving. The buzzing is the stepper in a stalled postion once its fully retracted, and this would be much the same as having the shaft jammmed up. To see if its working, get the engine warm, then unplug the stepper when the engine is running. Then switch off the engine, and remove the stepper and plug it back in. Let the engine cool, and then get someone else to cycle the ignition on then off (dont start) whilst you observe the stepper cone and shaft. It should pull back cleanly from its running position (when you unplugged it) to its cold start postion (fully retracted) as you turn the ignition OFF. You only get one chance to see it do this. Too dark to check AFM etc - although wires into the top of the plug look OK if a little exposed!
Just loathed to start changing parts randomly unless properly diagnosed......
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