high speed tickover

[snookes]

on the way home from a drive out on sunday the wedge (400se 1990)was ticking over at traffic lights etc at 1500rpm it normally ticks over at 1000rpm. any ideas?
thanks
anthony

[pwd95]

Sticky or faulty stepper motor. It used to do that sometimes when I had it. Take the stepper off & give it a clean.

[pwd95]

http://www.tvrcc-south-wales.co.uk/stepper.asp

[snookes]

thanks for the info

anthony

[snookes]

pwd95 said:

Sticky or faulty stepper motor. It used to do that sometimes when I had it. Take the stepper off & give it a clean.

i've cleaned the stepper and
it's still doing it, not all the time and if at a standstill it will (after about 3/4 seconds go back to normal tickover. Is first port of call change the stepper and where do you get them/cost?
thanks
anthony

[honestjohntoo]

Sounds like "idle speed hang-up" due to the throttle disc(s)not returning fully closed (or to the throttle stop if there is supposed to be a gap). The principle of the problem is explained from the index available here:
http://www.vintagemodelairplane.com/pages/Download...
6th item down.

Edited by honestjohntoo on Friday 25th January 10:05

[andymadmak]

snookes said:

pwd95 said:

Sticky or faulty stepper motor. It used to do that sometimes when I had it. Take the stepper off & give it a clean.

I've cleaned the stepper and
it's still doing it, not all the time and if at a standstill it will (after about 3/4 seconds go back to normal tickover. Is first port of call change the stepper and where do you get them/cost?
thanks
anthony

No, they all do that. You have a 400se? If its a hotwire engine there is a little electrical gizmo in the speedo drive line ( you can find it somewhere near the servo) This sends a message to the ECU that tells it that the car is moving. Whilst moving the car is ideled at about 1200rpm. As soon as the cars stops, the signal to ECU is changed, and the stepper takes the idle back to the lower level. (usually about 800) You can test this by disconnecting the speedo drive as it comes into the little gizomo from the gearbox. This will stop the higher idle state as the ECU will think the car is not moving.

ETA: The higher idle when moving is useful, especially in hot weather. I've left my gizmo in place and its fine.

Edited by andymadmak on Friday 25th January 10:06

[pwd95]

At a jungtion or wherever I'd stopped I used to put it i to first & just touch the 'biting' point of the clutch to bring the revs down.

[rev-erend]

Try clamping the pipe to the stepper motor when it does this .. if the revs drop then it's definately the stepper motor.

A common fix for this if to block the air pipe and drill a 8mm hole.. this allows a lot less air and
helps with the problem..

[dickymint]

Try a stronger throttle return spring (or an extra one). And clean the throttle plate and opening on the plennum.

[L33]

pwd95 said:

Sticky or faulty stepper motor. It used to do that sometimes when I had it. Take the stepper off & give it a clean.

Ditto what Wyn said.

[gsx600]

Ummmmmm I wonder why this car has been sold twice recently and both ex owners offering infromation on the same fix

Dodgy dealers or what

Or maybe its the shiny rocker covers I sold to first owner that's not sealed correctly

[dwgriffith]

Or maybe the base idle is set too near the upper limit for the range of the stepper motor to control?

[BadRedWedge]

dwgriffith said:

Or maybe the base idle is set too near the upper limit for the range of the stepper motor to control?

As Mr Griff says the first thing to do is set the base idle, the stepper motor can only cope with a certain range

Warm the engine up

Blank off rubber pipe to stepper

Turn adj screw and get the tickover down to about 500 rpm

Turn off the engine

disconect ECU for 20 seconds ( to reset it )

remove clamp from rubber hose

Start engine

No better ??

Next

Set throttle pot

Set AFM

See RPI website for details

Good luck

[snookes]

thanks for all the advice guys. i'm new to tvr ownership and never messed with cars before but not scared of getting my hands dirty, is it wise to buy the wedge bible from steve heath, will it help on repairs/little niggles etc

anthony

[GreenV8S]

snookes said:

is it wise to buy the wedge bible from steve heath, will it help on repairs/little niggles etc

Absolutely - should be compulsory for every new owner.

[djc1001]

As above with one addition - when you start the engine to check for improvement, move the car a few yards - for a full stepper motor/ecu reset you need one full cycle including the gizmo in the speedo cable recognising car moving - car stopped.

r's
david

[dwgriffith]

After an ECU re-set the engine will idle high for a while as the ecu re-learns where the stepper idle position is. Once the engine is started leave it running at idle until the speed stabilizes. There was a TVR technical bulletin to dealers on this one, however I can't find where I saved it. One other point I found on the pre-cat griff was that if the battery voltage dropped under cranking (in my case due to a poor battery connection) the ecu voltage went below that needed to retain the stepper setting above. The result was when started, the idle would be high and if driven straight away without the stabilization time, every junction, lights etc etc the engine would be idling far too high.

[GRIFFONMARK]

When I first got mine it would tickover at a fast rate (over 1500rpm) so I got into the habit of letting the clutch out a touch which would bring the tickover back down. However, I do use my car regularly, daily in summer, weekly in winter, and now it runs perfectly. If it makes a load noise and goes fast I wouldn't spend time worrying about it, just use it. Regards Mark