MG-Cars.info

Welcome to our Site for MG, Triumph and Austin-Healey Car Information.

Parts

MG parts spares and accessories are available for MG T Series (TA, MG TB, MG TC, MG TD, MG TF), Magnette, MGA, Twin cam, MGB, MGBGT, MGC, MGC GT, MG Midget, Sprite and other MG models from British car spares company LBCarCo.

MG MGF Technical - Still battling away

Hi All
Just looking for some advice.
I have been battling for a long time now to try to get the idle revs down from 1500 rpm following my installation of a GM throttle body onto my MGF. I have not yet checked all the electrics for bad connections, but I have cleaned up and jiggled the MEMS plug etc. as advised.
I did however notice that when holding the GM body up to the sun, a v. thin rim of light was visible around the top and bottom of the metal flap in the closed position. As far as I am aware, the flap is as closed as it can be, I have wound the adjuster screw right down. Is this normal? Surely where light can get through so can air. Does this mean that I have picked up a bad one at the scrap yard?

Thanks a lot for all the advice offered so far.

Cheers,

Jim
J. A. Farrington

The throttle butterfly could completely seal the throttle Jim.

I'm not that familiar with the GM throttle body - does it have a idle set screw? Certainly the TB used on the K-series has one - and this would certainly give a high idle (a bit like leaving the choke open). Perhaps Dieter can help more?
Rob Bell

Thanks v. much for the swift response Rob.
Not being totally au fait with the proper wordage I called the idle set screw the adjuster screw in my initial posting.
It's possible that I have the screw set too short and that the butterfly has gone too far (ie. beyond vertical), this I shall check this evening.

Cheers

Jim
J. A. Farrington

oops, sorry Jim, missed that in your original posting. But this is certainly the area that I'd concentrate on.

Fingers crossed that you get it to work!
Rob Bell

Further to the above...
There is also a small (grub screw?) projecting about 0.5 mm into the chamber of the TB, which I believe must be there to stop the butterfly in its flight beyond the vertical, as there is a corresponding dint in the butterfly at the edge, but I think that the dint may be too large and that the butterfly is now able to clear this hurdle. (This is sounding like a wildlife documentary.)
I will unscrew and examine the flapper tonight. Amazing how bouncing ideas off each other produces results.

All the best

Jim
J. A. Farrington

Jim, I have some images of the GM throttle body that Andy had - http://www.mgf.ultimatemg.com/Throttle_body/comparative.htm

Are any of these of use to you to aid your examination of your GM TB?
Rob Bell

Rob, I'll have a look and let you know the results of the evening's tinkering.

All the best

Jim
J. A. Farrington

Hi Rob

Just to say "Bo**ox to it." I have tried everything, and my skin is down to the bone on my thumbs from fighting to get the rear lower bolt to mesh into the thread.
I'm putting the crappy plastic one back on and will save up for the MG wider bore aluminum TB. I thought I had it cracked, it was ticking over steady at about 1000 rpm, but after a short spin out, I came in burbling like a dragster, popping and banging, with the engine trying to cut out. The exhaust was tinking from all the unburnt fuel going through it.
I will hang onto my GM TB creation, despite wanting to drop kick it over the wall, in case I meet up with Dieter one day, and he might be able to show me where I went wrong.
Cheers for the help anyway, maybe I should try something less ambitious.

Jim
J. A. Farrington

A pitty Jim :o(

I seem to recall that the MGFC had some 52mm TBs going pretty reasonably - might be worth phoning them up to see how much they are now :o)
Rob Bell

This thread was discussed between 07/09/2004 and 08/09/2004

MG MGF Technical index

This thread is from the archives. Join the live MG MGF Technical BBS now