Is tickover set mechanically or electronically

[S2 Giles]

Hi Folks

Just a quick question.
Is the 2.9i V6 tickover rev's level set by the ECU or by the mechanical rest screw on the throttle plate ?

Thanks

[tvrgit]

It's set by the ecu, which opens and closes the idle speed control valve which allows air to bypass the throttle butterflies at idle. Unless the throttle stop was holding the throttle too far open, that's how it works.

The throttle stop is factory set and shouldn't need changing.

The Idle speed control valves are notorious for gumming up and sticking, and it's worth taking it apart and cleaning it out with carburettor cleaner. Most idle speed problems on the 2.9 are due to this.

[tozerman]

The throttle stop screw you refer to still needs setting up, there was a thread on this a while ago but the link doesn't seen to be working, basically you must adjust the stop screw so that the voltage from the pot is set correctly, I have a copy of it somewhere, if you send me your address through my profile I will send you a photocopy.
Cheers.....Tony..

[S2 Giles]

The engine has just had some work, heads off etc and now its sitting at 1500 revs tickover and when cold it hunts and bounces off the anti stall ECU

Sticky bypass valves ?

Thanks

[S2 Giles]

OK so i have cleaned out the tickover air bypass valve with carb cleaner, but its not solved it

Basically its tickover is 1500 rpm and then occassionaly blips like its missing a beat. The blip isnt regular enough to be a plug or lead, i dont think.

When i unplug the electric connection to the tickover air bypass valve then the tickover drops to around 1000 as it should be. So if its not the air bypass then it must be the ECU ?

[phillpot]

Logically would have thought ECU fault unlikely, why should a (generally very reliable) component that has sat there doing nothing while engine worked on decide to play up ?
Personally I'd look again at any and every wiring connector, multi-plug etc. that could have been disturbed.
Maybe worth getting to a reputable garage and plugged into fault code reader ?

[S2 Giles]

Thanks

I'm going to check the connections and then re-set the ecu by unplugging, it can only be a faulty sensor telling the ecu to react differently or the ecu compensating for a previous bad reading

i'll update tomorrow

[Barkychoc]

A small amount of air getting into the intake system somewhere will cause fast idle.

[S2 Giles]

checked & cleaned the airflow meters
checked the cable block under the coil
checked & cleaned the air flow tickover valve

Still ticking over about 1400 rpm now

time to give it a blast and see if i can get it to settle down !
otherwise i'll have to try re-setting the ecu, just worried about doing that as i have the Dastek Unichip fitted and am worried it wont reset properly

[jwoffshore]

Giles, I have tried to forward some documentation to you by email, though I do not appear to have succeeded so far.....
Anyhow, besides the things you say you have already checked I would suggest the following:
1. Go through by logical process to eliminate air leaks. A vacuum gauge will assist you in this.
2. Check the throttle bodies to make sure they are not "gunged up".
3. At idle, the output from the throttle pot needs to be below 0.8 volts. If the output is above 0.8v, the idle function will not work.
4. Even if you have clenaed the ICV, there is a slight possibility it has failed.
5. Continuity check (using multimeter) on the wiring.

If you have not received the document I sent you, mail me back and I will send again.

JW

[mep12345]

Giles,

Check the earths as well - they can give similar results if they have a high resistance. If you want to check the operation of the sensors I have a fault code reader you can borrow and as you know I'm just down the road in Plymouth.

I'll PM you my phone number incase you want to get in touch to borrow it

Mark

[jimed]

You could have a simple issue where the throttle cable is set too tight so try screwing the cable end into the housing on the engine - you can't slow the tickover down from what the ECU sets but you can raise it - like having your foot down permanently a bit.
Jim

[S2 Giles]

So ive taken off the air channel tubes, blasted the throttle bodies & air meters. leaving them overnight.

Now need to check the tubes for any cuts or leaks. Having just had a load of work done, i wouldnt be surprised if they were thrown on the floor for a while or the exhaust welder cut them.

However, on a drive out all day today, it got better during the middle part of the day, sitting at 1000 rpm, however by this afternoon its back to 1500 again.

If all the cleaning doesnt work then its time to look at the throttle pot and then fault code reader

[Last S4]

S2 Giles said:

However, on a drive out all day today, it got better during the middle part of the day, sitting at 1000 rpm, however by this afternoon its back to 1500 again.

Given the info above I would be looking for a bad connection.
http://www.pistonheads.com/gassing/topic.asp?h=0&a...

[mep12345]

S2 Giles said:

If all the cleaning doesnt work then its time to look at the throttle pot and then fault code reader

Giles I also have a spare throttle pot you could use to swap to look for a change.

[S2 Giles]

Hi Mark

I havnt got a pm, but i think it would be good to have a chat (for me anyway)
can you email me on the new email i have just updated my profile with

Thanks
Giles

[S2 Giles]

OK, so a big thankyou to Mark

I have borrowed some parts from him & the first thing i changed sorted out my problem.

Yep, you guessed it...... Throttle Pot
TP was sending duff info to the ECU and it was trying to compensate.

I bought a used 'K Series' TP for 10 and bobs your uncle !!
Problem solved

The best news is that this means she is back on the road after a year laid up. I can start going back to the TVRCC meets and attend the SCH.

10 years of ownership and I still love it

[mep12345]

Glad it worked for you Giles - drop the stuff off when you are next my way, I'll give you a shout if I need any of it in a hurry but don't expect to

S2 Giles said:

I bought a used 'K Series' TP for 10 and bobs your uncle !!
Problem solved

For anyone who's interested the throttle pot is identical to the one fitted to the Rover K series petrol engines and is available for around a tenner rather then the £50 for the Ford part and I don't believe the Rover part needs the wiring mods that the later Ford ones require

Mark