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MG MGF Technical - TPS offset - Throttle body

This lunch I am going to attempt to fit my new 52mm TB.

The question is;

I will not be going to a garage to get the TPS offset calibrated.

On the throttle lever that opens the butterfly valve, do I copy the depth that the adjuster screw is turned from the 48mm body to the 52mm one?

And secondly.., is that waht needs reseting?

<do I mkae any sense at all?>
Neil H

Neil, don't touch the idle set screw - this is not something that usually needs adjusting. Just fit the TB and see how you go.

The TPS offset is a software setting in the ECU (it's the amplifier gain offset, if you're familiar with amplifiers). This can be reset by your dealer come the next service if the car is otherwise running fine :o)
Rob Bell

Good job I asked then.

Thanks Rob.

Getting all excited to feel the results now..
Neil H

Okay, jobs a good 'un.

Seems to work fine, though I was worried the idle was too high..
get to find out when I drive it home.

The stepper reset isn't meant to do anything to indicate success is it? (like beep, flash a light.. play a tune..?)

All I did was turn the key (but not start) and press the accelerator pedal 5-6 times..
is that all?


Neil H

What is the function of the TPS offset. When I fitted the 52mm TB a couple of years ago I did not have this re-set.

Should I have?
Steve Ratledge

If you've turned it off after this. that's all

Johan
Johan Slagter

>>What is the function of the TPS offset. >>When I fitted the 52mm TB a couple of >>years ago I did not have this re-set.
>>
>>Should I have?

Steve,
Read this: -
http://www.forums.mg-rover.org/showthread.php?p=514530#post514530

It appears you 'may' have to.

I'm just worried that pressing the pedal 6 times didn't seem to do anything.
I tried it before and after resetting and I can't notice a difference.

Neil H

The TPS is a rheostat with production tolerances - your MEMS will be set to the TPS of the TB your car was supplied with - it may not be the same as your replacement TB. 9 times out of 10 there isn't a problem: the offset for the new TB is in range of the old one, and every thing is fine - but it may mean that the ramp of the signal curve can be very steep to give a jerky throttle response.

As you probably take your car once in a while to a main dealer for servicing, you might as well get them to get the TPS offset and recalibrate as necessary.

Neil, the TPS reset is as you describe - but only 5 throttle depressions before switching off again.

A high idle can be caused by a throttle cable that is a little too tight: might be worth checking this, and checking to see whether the throttle pedal will give you maximum opening of the throttle butterfly.
Rob Bell

Ooo top tips! Thanks Rob.., will have a gander tonight.
Neil H

When I replaced mine, the idle speed was too fast. I swapped the TPS from the old throttle body with the new one and the idle speed was as it originally had been with the old throttle body. Saved a trip to Rover and very easy to do.
Paul Robertson

Ah! That's what I need to do Paul.. - I find that two junctions down the M40, and I'm doing 1,400 revs at the traffice lights..

Even had some burberry boy gunning his engine next to me last night because he thought I was offering a race... !!
Neil H

Neil,

Did you remove the TPS for any reason during the install?

I ask because the screws that secure the TPS to the back of the TB are too long, if you do them up completely the ends will stick out and foul the butterfly return spring, stopping the valve from closing fully and causing a high idle.

This can be tested for by manually closing the butterfly - if it catches and then makes a 'ping' type noise before closing fully then the screws are too tight and they are fouling the spring.

Other things to check...

Cable tension. Unclip the cable tensioner and spin it up the screw thread to give you a little more slack in the cable, then clip back into place.

IACV (Stepper motor). Follow the reset proceedure, if still no joy, dismantle and clean internal bore with Greygate plastic polish or similar.

----------------

The adjustment screw set the flow rate inthe bypass circuit, adjusting it basically sets the flow rate to match the expectations of the MEMS - so to do it properly you need to see the flow rate in the bypass circuit and be able to compare it to the expected flow rate in the MEMS - this means plugging it into Testbook. Mike Satur told me he was working on a method for setting it without the Testbook equipment, but he never came back to me to say if he had cracked it or not.

SF
Scarlet Fever

Also...

Remove the multiplug from the TPS and use some spray contact cleaner.

SF
Scarlet Fever

Didn't remove the TPS from the throttle body at all... I did obviously disconnect the old TPS and connect the new set though.

I might try what Paul suggests and swap the TPS over from the old one and see if that works (without doing the screws up too much!?)

I will also take the air hose off and see what the butterfly is doing..

Let you know.

Thanks for the good advice.



Neil H

Right.., last comment.

Took the whole thing apart again at the weekend..
By stretching like a ballerina (not a pretty sight), I was able to press the accelerator (right foot) and check the butterfly valve (left hand) - good eh?

Everything is fine. Full open, and full close.


I changed the TPS from my old plastic TB to the new alloy one, and instantly everything is hunky dory again.
So officially.., anyone changing to a new TB, might want to consider swapping this bit over. Its two screws and very easy.

Neil H

Good tip there Neil. Might be worth writing up some instructions carrying that suggestion! :o)
Rob Bell

Glad my suggestion worked for you too

All the best

Paul
Paul Robertson

This thread was discussed between 02/02/2005 and 08/02/2005

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