Idle hunting

[Landcrab1800]

Hi,
My 90 MG 2.0 i has the problem that the idle is not stable.

When I first got it (1 month ago)it seemed ok but developed the fault of nearly stalling on throttle down. I striped the throttle housing, cleaned the warming chamber, striped the idler motor unit. Also I cleaned out all the breather pipes.
I can not find the brass valve that people say needs cleaning, I have the MEMS system with a square filter.
There seem to be no other problems, pulls well, starts well and 31mpg av.
I disconnected the throttle switch and this stabilised the tick over albeit a little high (1500) so I bought a new switch, connected it up and the problem returned.
I have the Haynes manual for electrical management and will check the voltages this weekend but any ideas will be appreciated.

I like these cars and am glad others take the micky.
Less chance of them getting nicked, cheaper insurance and more for me but mostly I like the look on peoples faces when you prove how good they are.

Thanks

Gordon
:rage: :banghead:

[G Force]

[Hello there. I would start by making sure there were no air leaks anywhere, such as vacuum pipes, engine breather pipes, manifold gaskets etc. then make sure the spark plugs are in good order and the gap is set correctly. Plug gaps that are too wide or too narrow can cause uneven idle.

Sounds like engine could be running a little weak at idle, to try and confirm this you can disconnect the vacuum hose to the fuel pressure regulator and plug it. This has the effect of richening the fuel mixture at idle and if the engine is running too weak this should smooth out the idle. If this is the case then re setting the idle mixture is a garage job.

I personally think some of the injector cleaning products on the market are a good idea and could help your problem used long term.

Cheers Gary

[Landcrab1800]

Thanks,
I have changed the plugs, leads, rotor and dizzy cap, fuel filter, airfilter, oil filter and oil.

The plug gaps I am unsure about since there are a few to choose from but I opted for .8 mm.

As for air leaks, all checked, actually repaired one.

Will look at the fuel regulator,

Thanks

Gordon:beer:

[G Force]

hi, plug gaps 1.0mm 0.040"

Regards Gary

[derek mclean]

What brass valve is supposed to need cleaned? Is it perhaps something that has fallen out of the stepper motor? The older hot wire system had a valve that was easily lost if you weren't careful. Not sure about the MEMS. It may be similar. Somebody will maybe clarify this for you.

derek.