Idle Sticks at 1900rpm!

Idle Sticks at 1900rpm!

Author
Discussion

Tiggsy

Original Poster:

10,261 posts

251 months

Monday 28th April 2003
quotequote all
ok, i had a problem with the idle dropping, rising, dropping....stalling! so i cleaned the stepper- seemed a bit better but not perfect so i cleaned the throttle butterfly and housing (very fiddly)....now it idles at 2000rpm!

i thought it may be a sticky cable but if im sat still at 1900rpm and engage the clutch a little the revs drop- i would have thought if the cables stuck open then the car would pull forward at those revs?

any ideas? could my ham fisted throttle cleaning have buggered it up?

Tiggs

mongoose

4,360 posts

254 months

Monday 28th April 2003
quotequote all
given that cleaning the stepper didnt improve things significantly.i would first check that stepper is sealed in its housing properly,then check for air leaks around all induction side from airflow meter to plenum by spraying some damp start or similar arond all joints in pipework etc-revs will rise further temporarily as the high octane spray is drawn in to induction system through air leak.if all is clear after this,then check cable for snagging.on one of my old cars many moons ago,i put foot under accelerator pedal and lifted it to see revs drop back to idle speed.hope this helps-mv

Tiggsy

Original Poster:

10,261 posts

251 months

Monday 28th April 2003
quotequote all
how does the stepper get "sealed".....i just screwed it back in?

Tiggs

plipton

1,302 posts

257 months

Monday 28th April 2003
quotequote all
I suppose the stepper could be bu99ered, maybe.

Can you whip it out and turn on the ign - the motor's plunger should move in or out

mongoose

4,360 posts

254 months

Monday 28th April 2003
quotequote all
if its not screwed fully home,dirty threads damaged or missing washer etc.check the same way as for other air leaks.

M@H

11,296 posts

271 months

Monday 28th April 2003
quotequote all

Tiggsy said: how does the stepper get "sealed".....i just screwed it back in?

Tiggs


use some PTFE tape..


Matt

steveshutt

34 posts

251 months

Monday 28th April 2003
quotequote all
If I remember correctly from about 18 months ago, mine did this after cleaning the stepper motor.
I took it back off and pushed the end (of the bit that moves) so that it was fully retracted and then put it back in. This fixed it. I had noticed that as I cleaned it the stepper motor arm had moved fully out. (Sorry not very technical)
I don't know quite how it works or if it is just reset to its starting position when you switch the engine on but either this did it or the fact that when I put it back I got a better seal.
Hope this helps.

Tiggsy

Original Poster:

10,261 posts

251 months

Monday 28th April 2003
quotequote all
ok- help the morron time! PTFE tape? what is it and where will it be in B and Q! (i dont mean which ilse- just what section )

just to cheer me up......once i sort this should a TVR idle nicley like any normal car? im not stunned at the idea of having bought an £18k car that needs me to cover the gas at lights to stop it stalling!

T

M@H

11,296 posts

271 months

Monday 28th April 2003
quotequote all
PTFE Tape... plumbing section.. cheap as chips..

Matt.

Edited to add.. it should purr like a pussycat at the lights.. mine idles perfectly

>> Edited by M@H on Monday 28th April 13:16

mav

63 posts

266 months

Monday 28th April 2003
quotequote all
Hi chaps,
Just to chuck in my bit....
You must disconect the ecu after replacing your stepper motor. this enables the electronic bit to re-set itself.

Tiggsy

Original Poster:

10,261 posts

251 months

Monday 28th April 2003
quotequote all
ok so i do the SM again (i am just cleaning the dome on the end or do i dunk the metal section) (dome and spring it) in some whitespirit and give i t a good rub- can i be to rough to it?)

then i puts some PTFEFE stuff on the thread and wack it back- then check the jubile clip areas on the air pipe to the throttle chamber with some cold start- i assume if they leak i just tighten? or does PTFEFET work here to?

then i unplug the ECU?????? flippin heck! is that easy (i will consult the bible) any tips or is the bibles descrption enough?

Tiggs

joospeed

4,473 posts

277 months

Monday 28th April 2003
quotequote all
loose stepper won't flow enough air past the threads to make it rev at 1900 revs. The alternating revving you had previously was the fuel cut-off - the revs go up, the throttle pot shows closed throttle so the fuel cut off comes in, cuts fuel and revs drop instantly, the fuel comes back in close to 1200 revs and cycle starts again .. most cars with this habit keep revving rather than eventually stall though. it's not a stepper motor fault in my experience but an ecu / stepper communication fault.
there's a mod I do to cars like this to cure it - basically what happens is that once the idle revs go sky high the ecu doesn't recognise to bring them down again .. if the revs only get to 1600 revs then it all works properly .. a bit higher and it just stays there. By modifying it to limit the maximum revs the engine achieves to under 1600 rpm you cure this fault.
Joolz.

steveshutt

34 posts

251 months

Monday 28th April 2003
quotequote all
I cleaned all of mine and was quite rough with it, although it wasn't that bad. I have just read another post on the general tvr forum and one guy had to resort to very fine wet & dry paper because he had a small ridge on the sm and white spirit would not clean it.
I think you might be able to just disconnect the battery to reset the ecu (I have read this somewhere)
there is a full reset procedure where you have to connect to pin 20, but I don't think this is what they are talking about. That is for going back to factory settings.

Tiggsy

Original Poster:

10,261 posts

251 months

Monday 28th April 2003
quotequote all
jools- that makes sense- let me expalin the problem more clearly as maybe you'll spot something im missing:

Prob 1

Engine would idle at 1000rpm, then revs would fall to 200-300 and the car would "catch it" and rev back to a 1000.....few seconds later and it does it again, after 20-30secs it would not catch it and the revs would fall to 100 then conk out!

cleaned stepper- still did it

cleaned throttle butterfly and now it does this:

Prob 2

Either does what i described in prob 1, although it seems to catch it sooner....ie. the revs only drop to 500 before they return to 1000 hence it doesnt stall (although left doing this for over 45sec-1min it would stall at some point)

or

as i brake for lights, clutch in, the revs fall from wherever they were but stick at 1900. If left for a while they drop to normal (after 20-30secs) and back to prob 1!

if i give it a good hard blip they will sometimes drop to 1900 still or sometimes fall to 1000rpm...and prob 1!

if i let the clutch out a tad the revs drop, the car doesnt move....and then they go to prob 1!


Tiggs

ps- its a good job this car is bloddy fast otherwise i'd be doing my head in!!!

pps- buying tip- buy a car thats never seen rain = mint chassis and wishbones..........but a roof that leaks like like a cullander with extra big holes in!

mav

63 posts

266 months

Monday 28th April 2003
quotequote all

mav said: Hi chaps,
Just to chuck in my bit....
You must disconect the ecu after replacing your stepper motor. this enables the electronic bit to re-set itself.


ditto!!!!!!!!
hello
hello
this is what you do.
DO NOT DISCONECT THE BATT. TO RE-SET THE ECU


>> Edited by mav on Monday 28th April 16:21

Tiggsy

Original Poster:

10,261 posts

251 months

Monday 28th April 2003
quotequote all
mav,

are you saying thats what i do! or are you just clarifying the battery point in general?

am i being thick here....dont answer that!

T

ssbell

25 posts

264 months

Monday 28th April 2003
quotequote all
Tiggsy, what you describe sounds not unlike a Throttle Potentiometer (TP) problem. I see yours is a Chim but on an oldun like my S2, they can be prone to go wrong quite often, particularly if the car's not used much.

Replacement is not usually difficult and, being challenged mechanically, I had mine replaced for about £75 including the bits, the labour (and the VAT as I recall).. It was a couple of years ago, but I doubt things have changed much.

This is certainly worth investigating, particularly if you are just getting it roadworthy now for when the sun starts shining again. Soon, God, soon and I promise to be good for a bit.

Good Luck.

Simon.

steveshutt

34 posts

251 months

Monday 28th April 2003
quotequote all
Just had mine in today at the new tvr dealership (Gorners) near wigan for a tune up and general look over while its been stood around over winter. Been running it for a few weeks and it seemed ok anyway. Now iv'e got it back it is a bit smoother but I am getting idle problems like you describe, dropping to 200-300 sometimes catching it back to 1000, sometimes stalling.
annoying when it was fine before it went in.
I have to see what they say tommorow when it goes back ! pLus they can clean there mucky paw prints from all over it. Not a good start for them. I now have a keen interest in sorting this problem out.

steveshutt

34 posts

251 months

Monday 28th April 2003
quotequote all
Following my previous comment & mav's advice (Thanks, beers on me) I have just unplugged my ecu to reset.
Took it round the block and it seems fine.
(I just hope it is not an intermittent fault)
Tiggsy suggest you give it a go, before anything else.
I had best let Gorners know they need to do this !!

Tiggsy

Original Poster:

10,261 posts

251 months

Monday 28th April 2003
quotequote all
is it a simple job? unplugging it?

not gonna unplug the wrong bit am i?