When it starts doing it, push the throttle cam down at the bulk head end. If it settles throttle could be sticking.
Has it just started doing this or been like this since you got it?

 

I've had it since october. It never happened until after christmas. Around the time of HGF which is why I suspected that initially.

When you say the bulk head end I assume you mean the end of the cable inside the engine, or am I wrong?

 

No, I mean push the throttle cam the opposite way of opening it, I.E. no revs.

 

Got ya, do you think that is the same reason the car revs are rising and falling too? Whats the fix for it if that is the problem?

 

Either a good clean or replacement might sort it.

 

Cheers Ashy,

I'll try it. Will come back for more wisdom if it persists.

Thanks mate.

 

Ok so tried ashy's suggestion.
There was no movement in the throttle when I pushed to close it. Engine was idling very high this morning, 2k.

On the way home it was all over the place. Up and down.

:/

 

Usually a faulty CTS causes this, as the ecu gets bum information, it jacks out the stepper motor, mistakenly thinking the engines cold. If you don't have access to a testbook/T4, I would suggest for the price of them, a new coolant temperature sensor, it would be my first port of call, having looked at your video.
Best of luck
Brian.

 

Thanks man,

Is this the part, http://www.rimmerbros.co.uk/Item--i-MEK100060 ?

Easy to fit for an almost beginner?

 

Bit of a bump for this guys sorry. Problem has gotten worse today too though hence this.

Previous advice has pointed to CTS sensor. I've changed this and still no joy, I have an alloy TB, which would suggest it isn't sticking open. I've looked lately using forum searches and this could range from faulty MAP, IAC or TP Sensors.

I am assuming it's electrical as nothing mechanical could cause the previous problems, could it?

Well anyway the reason i'm now posting this as things took a turn for the worse today.
The car will not go above 25mph or 2k revs and is kangarooing MASSIVELY.

I've attached a link (http://tiny.cc/mgzr160) to the video of the revs jumping all over the place whilst it's in neutral. The fast pedal was held at a constant position, I reckon on a normal day would have held the revs at about 3k but look at what they're doing. I haven't got a ****ing clue. (My other videos of the car just revving itself are on there too).

Instead of spending money on individual sensors each time and trying one by one I have booked my car into the local MG service centre but I would like a head start on them if possible. Have any of you seen this before, what do you think the problem/s could be?

Things are getting desperate now, I just want this car to work properly

 

Try.I cleaned the throttle body. I also cleaned electro-magnetic vent (Idle Air Control Valve).
:idea:

 

It could be a miriad of things but sounds like a bad stepper motor or ecu driver:

throttle switch
stepper motor
blown stepper driver in ecu
vvc fault

have you any fault codes?
map sensor easy to eliminate, pull the connector off.

 

Ok this might sound strange but have you checked the spark plugs because on my old car it was doing the exact same thing so I tried the obvious tp sensor, idle control valve, mas airflow sensor etc but it still didn't sort it so I looked at my spark plugs and In the hole where the spark plug goes in was filled with a tiny bit of water. So once I dried it out the car was running perfect again. This probably ain't your problem but it's worth a check since it's free and take 2mins lol.

 

Hey there.
The very first video in this thread (the night one) is exactly what my ZR was doing.
started a few days ago, soon after i was in there getting my hands dirty checking the listed suspect sensors and valves, testing voltage & resistance. etc. this went on for a couple hours a day. no fix until
today- pulled my car up in front of the garage. as i got out, cleverly thought to perform the reset the stepper motor procedure as listed by Lawrence101. got back in the car closed the door and...

ignition off
wait 10 secs
ignition to no.2
wait 10 secs
push throttle to the floor 5 times(quick succession)
wait 10 secs
ignition off
wait 10 secs

start engine.....stepper motor reset

which i read on the forums this morning.
did the trick.

though i realize your problem has worsened. could still be the same fix.
hows it going over there?

 

Check all air carrying pipes to and from the inlet manifold and throttle body to make sure they're properly connected and tight, and also make sure non are degraded or split, an air leak can cause uneven idling and running. WD40 makes a good medium for checking potential leaks, simply spray on a decent amount where you think the leak is occurring and if you're right the engine revs will rise a little as the WD40 gets sucked in.

It's not all that likely compared to a faulty stepper motor, but worth checking all the same.

If I can think of anything else I'll post it back, but you find the problem dude!