PistonHeads.com Forum

s2 idle

Author
Discussion

kenpage

Original Poster:

321 posts

128 months

Thursday 6th March 2008
quotequote all
the only problem that i know of now is an old one i had before the rebuild the throttle response is slow to react,if its taken up to 3000 rpm from tickover and then you release the throttle it will drop to 2000 rpm and then take about 15 seconds to drop back to tickover @1000 rpm i have never managed to get the tickover below 1000 rpm i have just changed the throttle pot and its still the same i reversed the connectors on the air flow meters but no change, has anybody sufferd this and any ideas on what to do,next do you think the idle control valve could be at fault as i cant think of anythig else

ketvrin

3,504 posts

131 months

Thursday 6th March 2008
quotequote all
Hi Ken

it cant be something simple like a missing (or broken) return spring on the throttle linkage can it ? mine used to be slow to drop the revs before I replaced the spring

have a look at the picture on myphotoalbum... http://ketvrin.myphotoalbum.com/view_photo.php?set...

I hope its as simple as that

or a sticking cable perhaps ?

K wink

Edited by ketvrin on Thursday 6th March 12:52

Barkychoc

7,776 posts

126 months

Thursday 6th March 2008
quotequote all
Air leaking in through the servo?
Have you tried clamping the servo pipe flat with mole grips?
Don't drive it like this!

Could be an air leak elsewhere into the plenum.

Chris


Edited by Barkychoc on Thursday 6th March 13:04

Roy C

4,008 posts

206 months

Thursday 6th March 2008
quotequote all
You can test the idle control valve (aka Air Bypass valve) the same way you would test the throttle pot - unplug it (but only when the engine has been warmed up).

tvrgit

8,405 posts

174 months

Thursday 6th March 2008
quotequote all
Roy C said:
You can test the idle control valve (aka Air Bypass valve) the same way you would test the throttle pot - unplug it (but only when the engine has been warmed up).
Only problem is that unplugging the idle speed control valve puts the ECU into "service mode" where the ECU has various fixed inputs which over-ride many of the other sensors.

So unplugging the ISCV might remove the symptoms but only because you've effectively taken another (defective) sensor out of the ECU input loop.

Advertisement

kenpage

Original Poster:

321 posts

128 months

Friday 7th March 2008
quotequote all
hi checked the servo pipe its ok cleaned the airflow meters and the idle control valve stll the same throttle returns to the stop ok,so i then got braver i disconnected the idle valve better but still not right dis con each airflow meter in turn 1 made little difference but the other raised the idle to 2500rpm then went looking for an air leak and found that i had not connected the little rubber pipe from the back of the pressure valve to the front by the throttle bodies doh now it returns to idle much quicker but still to slow so i disconected the idle control valve again and it has cured the problem instant return to 1000 rpm idle, now as tvr git says i have solved the problem but probably not the cause unless i have a faulty valve it seems ok in its free and clean inside but how would i check it anybody got any other ideas?

tvrgit

8,405 posts

174 months

Friday 7th March 2008
quotequote all
Right this is going to sound a bit odd but mine does this every time I disconnect and reconnect the battery. I've never figured out why.

What I found was that if I leave the car to idle until the fan cuts in, and then goes off again, it doesn't do it after that (well not until I disconnect the battery again!). There must be a temperature sender that has to go through a complete cold-hot-cold cycle to reset it's range, and until it does, it's maintaining a fast idle through the ISCV because the UCE thinks the engine is still cold.

Obviously if you disconnect the ISCV it can't increase the air bleed to give the fast idle so all looks well... but you've cured the symptom not the cause.

I'd fix it if it bothered me long-term but it doesn't so I haven't.

mep12345

2,061 posts

123 months

Saturday 8th March 2008
quotequote all
Mine did the same after the rebuild and cleared in the same way as TVRgit described. I just assumed it was the long time standing, but perhaps he's right in that there is a sensor that requires a full temperature cycle.

Also mine now idles and returns to idle with no problems.

Note when I first started the engine I also went through the air flow meter connectors etc before the car just started to respond correctly.

Mark

grumpytvr

159 posts

155 months

Saturday 8th March 2008
quotequote all
Hi

I have had the same problem and I found it was a bad connection in the wiring to the throttle pot that runs along the top of the engine.

See here:

http://www.pistonheads.co.uk/gassing/topic.asp?t=255671 

Hope it helps

Tom

kenpage

Original Poster:

321 posts

128 months

Saturday 8th March 2008
quotequote all
hi update cleaned the multi connector that sits under the coil changed the water temp sender on the plenium and it now idles at 1000 rpm with the idcv connected. it it still slightly slow in returning back to idle from 3000 rpm back off and it drops straight back down to 1500 rpm and then to 1000 but i can live with that now i dont know if any of the above actually cured it,as said on the 2 posts it seemed a lot better when i first started it this morning before i started on it so may be it just needed to sort itself out also the rad has stopped leaking maybe i should have just put it all in the garage and let it fix itself many thanks for the replies.seats in tomorrow carpets to stick back down, later on in the week the bonnet back on and then the mot

clarenceboddiger

1,398 posts

137 months

Saturday 8th March 2008
quotequote all
tvrgit said:
Right this is going to sound a bit odd but mine does this every time I disconnect and reconnect the battery. I've never figured out why.

What I found was that if I leave the car to idle until the fan cuts in, and then goes off again, it doesn't do it after that (well not until I disconnect the battery again!). There must be a temperature sender that has to go through a complete cold-hot-cold cycle to reset it's range, and until it does, it's maintaining a fast idle through the ISCV because the UCE thinks the engine is still cold.
I have had similar things to this on Peugeots, whereby after discnnecting the battery you have to drive the car up to certain speeds in each gear and hold them for a while in order to reset the ECU, sounds like a similar scenario.

mikee boy

967 posts

173 months

Saturday 8th March 2008
quotequote all
Dad, make sure the 2 air flow meter plugs are the right way round. Glad to
hear it's running.

I'm back on Weds. It's nice in Florida.