[g259fsg]

BTW, what workshop manual are you using. I've just looked at the Haynes manual and realise my SPi car is somewhat different to your MPi model. They do have some info on setting up the accelerator cable and TPS on pages 4C-3 to 4C-7 for the MPi model. It mentions in connection with the TPS (potentiometer) to check the the throttle can go from fully open to fully closed.

[lsowden12]

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.

Yeah made sure the cable was tightened to a decent amount the other day so I think that's alright. I do think its either the tps or the stepper motor. The tps is very easy to replace, the stepper motor is bolted onto the throttle body inside a metal housing because its the alloy inlet so theres no info online about how you remove or replace it or whether its even something you should actually attempt. Has anyone ever heard of the stepper motor being removed from inside the throttle body with it bolted inside before? Don't want to try get it out only to find doing so will make the situation worse

[lsowden12]

Yeah made sure the cable was tightened to a decent amount the other day so I think that's alright. I do think its either the tps or the stepper motor. The tps is very easy to replace, the stepper motor is bolted onto the throttle body inside a metal housing because its the alloy inlet so theres no info online about how you remove or replace it or whether its even something you should actually attempt. Has anyone ever heard of the stepper motor being removed from inside the throttle body with it bolted inside before? Don't want to try get it out only to find doing so will make the situation worse

Nevermind, thats incredibly inconvenient given the circumstances



Worst case scenario does anyone know where I can get a replacement alloy inlet TB without paying £700 for the rimmers one

[Mr Teddy Bear]

Look for a L Reg' 214 being broken?

[crepello]

Yeah made sure the cable was tightened to a decent amount the other day so I think that's alright.

The book way to set the cable is to ease the square rubber out of its fork on the throttle body, and hold it against the
'pedal' side of its fork, adjust to just remove cable slack, then put it back into the fork. This leaves the Rover-prescribed
amount of cable/pedal pre-travel.

[lsowden12]

Right problem solved, it’s both the stepper motor AND lambda sensor. If the stepper motor is plugged in and the lambda is disconnected the problem is still there, the same is true in reverse. But if both are unplugged, sure the idle is at 1500rpm but there’s no fluctuation and the idle never leaves the 1500 spot no matter how much you drive which is usually not true as per the video yesterday.

[g259fsg]

Interesting. To run steadily at 1500 rpm, I would think the engine needs to be getting sufficient air. I'm suspicious that the throttle valve may be slightly open for some reason, maybe it's stiff or being held open by the stepping motor even when it's disconnected. Or it could be air getting in by an "unauthorised" route. Have you tried disconnecting the accelerator cable at the throttle valve and see how it feels to move it. I don't know about your car, but I think mine has a return spring to close the throttle when it's released. The integral stepping motor might complicate things. Have you worked out how the ECU on your car knows whether it's in the drive mode or idle mode? There has to be something to tell it when to use the stepping motor for adjusting the throttle.

Hugh

[lsowden12]

Interesting. To run steadily at 1500 rpm, I would think the engine needs to be getting sufficient air. I'm suspicious that the throttle valve may be slightly open for some reason, maybe it's stiff or being held open by the stepping motor even when it's disconnected. Or it could be air getting in by an "unauthorised" route. Have you tried disconnecting the accelerator cable at the throttle valve and see how it feels to move it. I don't know about your car, but I think mine has a return spring to close the throttle when it's released. The integral stepping motor might complicate things. Have you worked out how the ECU on your car knows whether it's in the drive mode or idle mode? There has to be something to tell it when to use the stepping motor for adjusting the throttle.

Hugh

Had a look the other day when I ran without an air filter, the valve stays closed and acts as normal when the pedal is pressed. Not sure about what the ecu thinks is happening but I assume based on the fact that the whole operation of the car changes dramatically for the better when two things are unplugged tells me that perhaps it is the ecu and there actually isn’t anything wrong at all, it just thinks there is. Like I say this all started the day after I was disconnecting and reconnecting the battery all day because I was looking for a battery drain so I wonder if I’ve screwed the ecu somehow by doing that.

It is however very drivable without the stepper motor or lambda sensor, means I can get to and from work every day without having to restart the car every minute because it’s either died or is idling at 4k haha

[g259fsg]

That's good that the car is useable. If the idle stays at 1500 rpm it's not a major issue. It would be interesting to know what the exhaust analysis shows when it's idling at 1500. The fundamentals remain, however, the engine is somehow getting enough air and the ECU injecting enough fuel to tick over at 1500 rpm, without the stepping motor connected. If I want my car to idle at 1500, I have to have my foot gently on the accelerator to open the throttle. I sometimes set a fast idle when using a flushing agent before an oil change. To get 1500 to 2000 rpm, I wedge the throttle slightly open at the engine.

Don't know if you've investigated this, but on the Members Area of the Club website, there's an excellent library of workshop manuals, including manuals for the engine management. There should be one there for your car. That might give more insight into how it's operating in the drive and idle state.

Hugh

[lsowden12]

Was unaware of the technical articles directly on this site but thats helped a lot.

In other news, after a bit of research, whilst its not immediately obvious, it would appear that the Rover Mini SPi uses a very similar throttle body design where the stepper motor is integrated into the throttle body itself. The plug itself, the tps and the housing surrounding the stepper motor looks identical. The TPS has the exact same part number and I have a feeling that also applies to the stepper motor mechanism which is NLA for the R8 but not for the Mini and therefore not as "non removable" as the technical manual suggests. There's nothing that links the 200 mk2 and the Rover Mini stepper motors directly but I am now 99% sure it's the same part. For the sake of "science" I am now very tempted to get my hands on a Mini SPi stepper motor and replace it with the one in the 214 and see what happens. The plug will fit, its whether the ECU reads the information any differently or not