[Mr Teddy Bear]

Yes I checked my stock and the ECU part number differs, my 414 must have been of late 95 manufacture, because it had the plastic manifold and a different fuel filter [ they look the same but are not!].

[lsowden12]

I think I was actually wrong. This whole ordeal keeps getting more and more confusing. I spent today messing around with literally everything. Ran it without any vacuum lines attached, unplugged the lambda sensor, tested multiple states of the stepper motor by unplugging it randomly. One thing I did notice though was when the throttle position sensor was disconnected, the car did not behave any differently. I’m sure the car has a preset that it defaults to when the tps has gone rogue because I would have assumed disconnecting the tps would have immediately caused the car to go crazy yet it was idling rough and, stalling and high idling exactly the same as it usually does as if the tps wasn’t actually doing anything at all

What I now think is happening is it’s not the ECU resetting that solves the issue when the battery is disconnected, it’s the tps resetting itself which then proceeds to break itself again after a while like it’s being shorted out or isn’t properly remembering what it needs to do. I am determined to find the actual cause of this problem not only for me but also potentially for anyone who may have a similar issue outside the usual blocked vacuum pipe / air leak / stepper motor reset etc; suspects

If that doesn’t work then I think it could also just be the stepper motor. Like I say, every time you turn the car off now it resets itself and clicks 3 times as if you’ve done the reset procedure even if I haven’t. I now understand it’s only meant to perform a series of clicks once. I’m assuming that could still be related to the tps which is pretending the pedal has been pressed 5 times because it’s malfunctioning and is telling the stepper motor to reset every time but I’m not sure if that’s a thing that could be happening or not. It’s the throttle body where the stepper motor is attached and bolted directly on so I don’t actually know how I’d replace a broken stepper motor however. I’m going to replace the tps and go from there

Absolute final thing I would guess is the timing is out. If it gets to the point where I’m replacing the whole belt and retiming it and that doesn’t work I think I’m just going to swap another engine into it because it’s probably just a lost cause at that point haha

[g259fsg]

On my car, a 1990 SPi 214, there is also an accelerator pedal switch that detects that the accelerator pedal is released and this tells the ECU to do the idle routine. According to the manual, this switch must be closed. Worth checking you haven't got an intermittent connection there.

Hugh

[g259fsg]

One further thought about the TPS. I do admit I don't know exactly how this system works. Assuming when the accelerator position switch is closed it tells the ECU to idle, then it won't be reading the TPS signal, just adjusting the stepping motor to keep a steady idle speed measured by the crankshaft sensor. On my car that is around 900 rpm. If I switch on some electrics (headlights, rear heater etc.) the revs dip momentarily as the alternator starts delivering current and then come back to the normal tick-over. This shows the idle control system is working.

The fact you could disconnect the TPS and it made no difference to the erratic idling maybe confirms that the ECU isn't reading it in the idling state. It is possible the stepping motor is defective and although the ECU is sending the right signals, the stepping motor isn't responding correctly.

Does the car drive normally on the road? For example does it accelerate as you'd expect and climb hills no problem? If it does, then it's likely the TPS is working correctly as that is the only way the ECU would know to inject more fuel to give the extra power. You wonder about the timing belt, but I would expect a timing fault to show up with poor on-the-road performance. One final test, can you set a stable fast idle, say 1500 to 2000 rpm, by gently pressing and holding the accelerator pedal. In this mode the TPS would be active.

Hugh

[lsowden12]

I mean it doesn’t act normally when driving really, hills and maintaining speed is okay, the second you come on or come off the throttle the whole car violently lurches or jumps a few times before returning to a smooth acceleration/deceleration, especially if you press the throttle to the floor quite quickly then come off really fast then get back onto the throttle . I believe people refer to it as kangarooing. Sometimes the only way you can stop it is by slipping the clutch into the same gear again. Thing is as commonly as I see that term it’s never fully established anywhere what actually causes it so I’ve lived with it ever since I’ve owned the car

[g259fsg]

That does sound bad, and more than just an idling problem. Could well be a problem with the TPS or the ECU. I assume you've no reason to suspect there is anything else wrong with the engine. Think you showed a video of a lot of smoke a week ago. Did you get to the bottom of that? Have you done a compression test and checked the static timing on the timing belt? One thing about fuel injection under computer control, it will try to compensate if something else is wrong. You've done the right thing to eliminate as many other potential faults as possible.

[lsowden12]

The thing with the smoke issue is I don’t even think it’s head gasket because it goes away and there’s no other telltale signs of it existing. It happens a few times but only after I try to reset the stepper motor too many times. But then again I have no idea what it could be other that head gasket because I don’t know of anything else that can burn thick white smoke like that whilst also simultaneously going away on its own

[lsowden12]

Here

https://youtu.be/0KCZRgu9F-E?si=_9yXPXbYrVEaLvjC

This video will be really useful for diagnosing the problem. It’s long but it makes it very obvious what’s happening and I think someone might pick up on what it is based on how it’s behaving in that video, it’s very linear and predictable at times

[SteveB]

Oil tends to burn blueish, if it’s nearer to white it’s more likely to be water i.e. steam, which would also dissipate quickly. It could be the inlet manifold gasket. If the gasket starts to leak, coolant can get sucked straight into number 1 cylinder and out the exhaust, looking for all the world like head gasket failure.

If you’ve got an Android phone it might be worth looking at the RoverMems app. You’ll need a cable – around £30 for the round 3 pin version. You’ll be able to access fault codes on the ecu relating to various sensors and also see live data with the engine running. It might just tell you the tickover’s all to hell, but it might also point you in the right direction.

[g259fsg]

I agree with SteveB, the exhaust "smoke" did look like steam but could include coolant. Last week you said it smelled of burning. I've found the 214 exhaust pipe can collect condensation inside which evaporates when the engine gets hot and makes a quite steamy exhaust.

Thanks for the new video showing the rev counter. The normal idling looks spot on. You would expect a little bit of dither as the ECU alters the stepping motor position. Did you try switching on electrics to see if the ECU control brings it back to 900 rpm? I've only seen the symptoms you show when my car is cold. The revs are a bit high, up to 1500 rpm but it comes back down after 20 to 30 secs. You would think the ECU would be trying to get the tick-over to 900 rpm, so it's odd that it stays stably at 1500 rpm idle with the engine hot. What's the ECU doing? One very simple thing to check is to make sure the throttle is properly closing at the air intake. A bit of resistance in the accelerator cable or stiffness round the throttle spindle may make it stay a bit open. Easy to check by pushing it gently to see if it still slightly open. The stepping motor might be doing something funny after you've rev'd the engine, and isn't closing the throttle properly.

However, none of this explains the kangarooing, which from your post sounded pretty severe.