Can you ajust the tps ? High idle issue

Post Tue Apr 07, 2015 10:01 pm

Right, after quite a bit of graft , my engine bay is now looking great

Today it's had a new inlet manifold and rocker and a BBTB big bore throttle body , so its all been apart , it has a new thermostat housing recently, new thermostat etc but ran fine

It's just idleing at about 1000rpm with the mixture screw tight , can't move it any lower

just wondering how I can fix this ? Is it possible to ajust the TPS ? Ie remove it move it around a bit or something ? The icv is clean as is everything else

Not had a chance to fiddle yet, after getting it all fitted today and taken it out for a bit of a run out this evening to let the ecu sort itself out , all seems to be running fine no issues , the BBTB seems to have made a nice little difference bit more perky

Appriciate any advice ?

Cheers

Post Tue Apr 07, 2015 10:35 pm

Mixture screw?? Only if you've fitted a carburettor. If you mean the CO adjustment on the AFM, I hope you marked where it was. Put it back exactly where it was, and don't touch it again.
Is the throttle cable adjusted properly, and not holding the butterfly open slightly?
The throttle body has an adjustable stop for the butterfly on it - another adjustment that should never be touched, but if your TB has been enlarged, the original adjustment is no longer applicable, and may not be set correctly. BMW special tool needed to set properly.
TPS has to be adjusted after the throttle stop is set, and has to be set to switch from the idle map immediately after the butterfly leaves the stop, consistent with reliably switching back again when the throttle is closed.

Post Tue Apr 07, 2015 10:35 pm

If you disconnect the battery or ECU, you should let the engine idle for at least 10 minutes to enable base idle settings to be learnt, then switch off, then take it for a drive throughout the rev range. This ensures full data transfer from the EPROM to the processor.

The idle speed is set by the Motronic system - I don't think it's adjustable, as such, unless you change the hex value of the idle speed part of the map.

Post Tue Apr 07, 2015 10:48 pm

Cheers guys, it's all a bit above me , I ment the little screw on the throttle body ? The one you can ajust slightly to alter the idle ?

The afm has not been touched , and yes it was left to idle for 10 mins well longer to come up to temp etc and bleed the coolant system

But being a new TB and bigger bore, it needs to all be set up and ajusted ?

Post Tue Apr 07, 2015 10:55 pm

The butterly stop thing brian that should never be touched, would that vary on it being a TB from another car ? (Not my original) and also having the big bore conversion ? And then being fitted to my car ?

I presume it all just needs ajusting and setting up ? Is this something I can fiddle with or should be taken to someone professional ?

Post Tue Apr 07, 2015 11:37 pm

The throttle stop requires the use of a BMW special tool to set properly, so the 'someone' would have to be a BMW dealer.
However, the method I use on the rare occasions I need to, is to remove the ICV and either block both hoses, or plug one port of the ICV and refit it, then to start the engine and bring it up to temperature. I then adjust the stop so that the engine is idling so slowly that it is threatening to jump away from the engine mounts.
Once this is done, the throttle body needs to be removed and the TPS adjusted in its slotted mounting holes as I described in my last post.

Post Tue Apr 07, 2015 11:52 pm

The only gains you will get from an M20 BBTB is space in your wallet and drama's with idle.. spend 10 mins fitting your old TB and see how it runs ?

Post Tue Apr 07, 2015 11:52 pm

Could you alternatively set the butterfly flap gap with a feeler guage?

Post Tue Apr 07, 2015 11:59 pm

jimbom30cab wrote:Could you alternatively set the butterfly flap gap with a feeler guage?

IMO, no.

Post Wed Apr 08, 2015 12:08 am

So what should I do brian ? Take it to Bmw ? It sounds a bit beyond me

What would you do in my situation ?

Would be interesting if anyone else who fitted a Bbtb could comment on what they did if they has idle issues

Post Wed Apr 08, 2015 12:12 am

e30topless wrote:The only gains you will get from an M20 BBTB is space in your wallet and drama's with idle.. spend 10 mins fitting your old TB and see how it runs ?

Most people dont consider that Mr Schmitz (or whatever the coonts name was) spent hundreds of hours setting up an ECU map to work with a particular sized throttle body and a particular profiled cam etc etc to get the best drivability from the engine, if Mr Schmitz would have thought a larger throttle would make a significant improvement im sure the engine would have come with that throttle from new

Post Wed Apr 08, 2015 12:34 am

DanThe wrote: Most people dont consider that Mr Schmitz (or whatever the coonts name was) spent hundreds of hours setting up an ECU map to work with a particular sized throttle body and a particular profiled cam etc etc to get the best drivability from the engine, if Mr Schmitz would have thought a larger throttle would make a significant improvement im sure the engine would have come with that throttle from new

My theory entirely Dan,
Millions spent on development back in the 80's is no match for fred in a shed with an Aldi laptop and a various black and decker tool assortment,

I shall name no names but a well known zoner... went to a dyno day with his polished BBTB/speed touch chip and produced a whopping 96bhp in his rampant 325i, only to be slayed by a 318 touring producing 104bhp, He took home the wooden spoon award...

Luckily i was on hand to sell him a standard TB and ECU which got him back up to an almost respectable 160 bhp

Post Wed Apr 08, 2015 12:55 am

96bhp a˜³ lol

Tbh the car feels good and certainly not worse and it seemed to pick up nice and great when changing down a gear , Ive read s few zoners have fitted BBTBs with good results ? Jimbo said it was excellent perked it up and improved mpg

Not had a real good drive just a little run out and didn't give it much as ive got shit tyres on at mo and having just put it all back together just took it for a gentle runout

Post Wed Apr 08, 2015 8:37 am

e30topless wrote: I shall name no names but a well known zoner... went to a dyno day with his polished BBTB/speed touch chip and produced a whopping 96bhp in his rampant 325i, only to be slayed by a 318 touring producing 104bhp, He took home the wooden spoon award...

Luckily i was on hand to sell him a standard TB and ECU which got him back up to an almost respectable 160 bhp

Well, since you did mention my name, I might add that the chip may not necessarily have been at fault there if other aftermarket parts had also been added such as BBTB, etc.

Post Wed Apr 08, 2015 8:40 pm

My 2.7,with BBTB,struggled this year at MoT time and is noticabley running rich at idle.
TPS clicks as it should,but there's a flat spot just off idle that shows it's self both when opening the throttle and closing it at 750/1200rpm.

My thoughts are air leak,possibly from the rubber bung on the base of the t/b,but reading the above leads me to try the stock item and see what happens.
When the BBTB was first fitted,I gained about 5% in fuel economy with no drop in grunt,but I'm not now covering the long distances that I have been in recent years so the fuel consumption is now less important.

Indeed,from one MoT to the next,the cabbie travelled less than 800 miles....by comparision my S Type(bought 6 months ago)has covered almost 6k!