Welcome to our resource for MG Car Information.



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 - Observations on fitting new throttle body

Just finished fitting new trophy throttle body to my 1.8i and came up with the following observations:
1) Although access to the throttle body is fine from the boot, I found reaching the bottom bolts very difficult and the furthest bottom bolt impossible without removing the engine cover.I didn't have an 8mm ratchet ring spanner - this probably makes all the difference! However, the bottom pipe to the TB at the back has a clip on it that needed pliers - again this would be a nightmare to unclip and put back on without first removing the engine cover. I admire those of you out there who've done it in just 40 minutes and without removing the engine cover!
2)Once back on, I followed procedure and reset stepper with 5 pushes of throttle etc. Car started fine but I noticed an initial high idle speed and an unwillingness to rev down when the throttle was blipped. I put this down to the engine being cold and MEMS needing more chance to adapt to throttle positions and so I took it out for a quick test drive. Despite a thorough warm up and varying driving speeds, the throttle would not quickly return to idle, idle speed was still high (approx 1300 rpm and would often exceed 3000 rpm which a throttle blip would fix)- in fact all the symptoms described by others on this BB of a warped TB or sticking butterfly valve.
Once back in garage I adjusted throttle cable by slacking it off a touch to ensure butterfly valve was closed properly. This fixed the problem completely, with no loss of throttle response.
3) Initial thoughts on performance - throttle response seems to have improved slightly and there seems to be a power gain at the top end of the rev range. My 1.8i has now become a VVC!

Nice one Phil, where did you get your TB and how much?
Wise Crack

I think that because this has proved a popular change to make, there is now a shortage of TBs - at least a months wait I believe!

Dr Dave (Richardsons of Tiverton in Devon) received a supply on Thursday 9th May and quoted me "117.80inc VAT and P&P delivered to your door within 72hrs". I phoned through my credit card details and one arrived within 24 hrs. You can reach him on 01884 256851.



to 2)

the other probable failure could happen if the body is poor sealed to the inlet plenum.
Could happen if the bolts are loose or any dirt gets between the parts while assembling.

BTW. I can't get why some try engine works without removing the engine cover ?
It's quick and easy to remove the cover, though.

Dieter Koennecke

TB was approx 112 from B&G, and arrived within few days of ordering.
Thanks, Dieter - I came to the same conclusions myself - the symptoms are caused by an uncontrollable air leak into the system. I noticed when taking off the plastic TB that the bolts were not torqued on very tight anyway, but the O - ring seal seams effective as it stands slightly proud of the mating surface.

Fitted mine a week ago. About 40 mins with the engine bay cover off (after I purchased an appropriate spanner*).

On point 1) 'the bottom pipe to the TB at the back has a clip on it that needed pliers' - I found the pipe just pulled off with the clip still on......easy job.

*To anyone thinking of fitting the TTB do yourself a favour and get yourself a ratchet spanner before starting the job, your socket set will be useless

It certainly makes a difference on the MPi :o)

tim woolcott

Currently I am having idling problems with my current old sort plastic type throttle body where it seems to dance around a bit on idle when cold and revs don't drop of immediately.

Although I think it has got worst since it went in to my dealer for a diagnostic check where they adjusted the stepper motor.

Maybe I need to think about a new TB.

What is the main difference externally on the TB and will I need to tell insurance company if I fit one.

Tom Randell

Hi Tom,

The Trophy TB is a bright ali colour. Otherwise it is identical in external appearance.


>>What is the main difference externally on the TB and will I need to tell insurance company if I fit one.<<

There are no external differences - except that your original TB is plastic whereas the new one is alloy. But on MY2000 cars, the standard 48mm TB is also alloy...

Technically, you should inform your insurance broker of all modifications. In practice, I suspect that many do not, and frankly, the insurance assessor would have to be exceptionally on the ball to even pick up on the fact that this was not an original fitment part - and even more aware of the MGR modification scene to work out whether this replacement part was a 48 or 52 mm TB...
Rob Bell

I guess if something should happen to your existing throttle body, like all the bolts came loose and it fell off the car.

And then you ordered the wrong part from the parts department....

paul weatherill

... or Cat Logistics delivered the wrong part (alarmingly plausible that) ...
Rob Bell

...Or you had problems with idling which indicated the existing plastic TB had warped or twisted, necessitating a replacement...

...just like my engine had trouble breathing, hence had to by a K&N????

paul weatherill

No the K&N is a performance mod, however removing the nicks and casting errors and smoothing out the internal surfaces is purely cosmetic, you can't see it but then this is the darkside...

Will Munns

This thread was discussed between 13/06/2002 and 18/06/2002

MG MGF Technical index

This thread is from the archive. The Live MG MGF Technical BBS is active now.