V8S idling problem

[TVRNick]

I have a very odd problem with my V8S

It runs really nicely, untii i pull up at traffic lights, carpark etc when the engine will rapid idle at 2000- 2500 rpm and very, very slowly settle down to normal If i put in gear & let in the clutch slowly to biting point it will return to base idle

Any advice hugely appreciated

[v8s4me]

Check out your stepper motor as a starting point. Could be a broken wire or a sticking piston. I think there might be something in the Steve Heath manual about how to check the unit.

There's plenty of info here on PH if you search. It's a common problem on the RV8 so you may also find help on the Chim & Griff Forums as well.

I think I've got a used stepper motor somewhere if you need a replacement.

PM me your email if you'd like my list of surplus to requirements V8S parts.

[GreenV8S]

Clean the stepper motor. They get gummed up and stick. Also check that the outside edge of the throttle plate is clean since that can stick too and prevent if from closing fully. Also check the condition of the throttle cable inner at both ends - a damaged frayed cable can stick.

[v8s4me]

GreenV8S said:

..... Also check the condition of the throttle cable inner at both ends - a damaged frayed cable can stick.

Good shout. If the cable is frayed at the accelerator pedal it won't be long before the cable snaps at that point and leaves you stranded.

It might be worth checking the inner cable isn't sticking in the outer and is free to slide. Something as simple as that would cause the problem you describe.

There's loads of helpful advice on here about throttle cables, start here

https://www.pistonheads.com/gassing/topic.asp?t=11...

[TVRNick]

Thank you all for your input

I have checked the throttle cable and it seems perfect ...move freely and no fraying

Next job will be the stepper motor but this was cleaned recently and base idle reset

The fault only happens after a few miles has been driven and engine thoroughly warmed up

I am wondering if its an electrical issue as the speedo only works when warmed up and the oil pressure reads low I have changed the sender and the gauge with no effect The pressure is good , 35- 40lb on a mechanical gauge

[GreenV8S]

TVRNick said:

the speedo only works when warmed up and the oil pressure reads low

The original senders and gauges are simple analogue devices, so unless you're converted to electronic it would be worth checking voltages through the system. For example poor connections in the fuse box or wiring loom could throw the voltage out.

[v8s4me]

[quote=TVRNick].............. the speedo only works when warmed up ............./quote]

That's not unusual. Mine was like that for years and when I finally fitted a new sender it made no difference.

Don't be tempted by suggestions to use ATF in the gearbox to solve this problem as you will just cause yourself other problems. Just live with for now but next time you are under the car try and get to the wires from the sender to make sure there are no cuts/fraying as this can cause all sorts of issues.

[GreenV8S]

v8s4me said:

Don't be tempted by suggestions to use ATF in the gearbox to solve this problem as you will just cause yourself other problems.

Absolutely! And ignore service bulletins from TVR, dealers and so on that try to tell you otherwise.

I was lucky enough to get my LT77 rebuilt by the man who designed it a few years ago, and when asked about oils he said that if I used ATF he was going to box my ears. It was a huge bodge to get around a minor cold weather usability problem and no doubt lead to a lot of post warranty failures.

[TVRNick]

my gearbox has ATf in it. I did query with the dealer as the handbook specifies SS80 but they insisted that ATF is correct Should i have the box drained and refilled?

[GreenV8S]

TVRNick said:

they insisted that ATF is correct

So did Land Rover and all their dealer network. So did the TVR factory and many TVR specialists who listened to them. They were all confident and authoritative. That doesn't mean they were right.

[v8s4me]

TVRNick said:

.... Should i have the box drained and refilled?

Yes! Use Difflock.. From the blurb...

" If you are still using ATF,Dexron ll or MTF 94 in your LT77, R380 or other 5 speed manual box then you should think again because they are poor at preventing wear, shears down under the action of the gears and thickens as temperatures drop. This leads to shorter gearbox life and poor, notchy gearchanges, especially 2nd Gear on cold mornings.

A fully synthetic gear oil can solve these problems but it must be specially formulated to give the best possible results. Our EVOLUTION 1 is specially created for Land Rover Transmissions. It has the perfect viscosity required and its high film strength prevents metal to metal wear whilst reducing gear and bearing noise. "

[phillpot]

What a surprise, the manufacturers say their oil is the best to use!

Nothing like an impartial, unbiased opinion

[v8s4me]

Well it transformed my gearbox so for me, it did what it said on the tin

[Oldred_V8S]

Or Castol SMX. Made my gearbox silky smooth.

[phillpot]

Oldred_V8S said:

Or Castol SMX. Made my gearbox silky smooth.

Same stuff near as damn it, fraction of the price?

[zombeh]

TVRNick said:

my gearbox has ATf in it. I did query with the dealer as the handbook specifies SS80 but they insisted that ATF is correct Should i have the box drained and refilled?

Depends on what's in it and how many miles are on the box since it was last rebuilt (and since the last oil change).

If it's a really good modern synthetic ATF like the silkolene one with a different sticker on the bottle (difflock) and it's been in there less than 20,000 miles or so then it's fine.
If it's whatever dexron2 was knocking about or it's been in there ages and the box has never been rebuilt then I'd get it out and put something half decent in.

When you're reading stuff on the internet about it do realise that the V8S gearbox is a H suffix 2wd box so it's got the wide gears, big bearings and redesigned synchros but the early half size oil pump.
Significant large parts of the gearbox are made of unobtanium and the box as a whole complete unit is specific to the car (though all the individual bits of it are used in something else and it's almost the same as other TVRs, morgan etc) so it's worth looking after.

[blaze_away]

If you still have the high idle at junctions then I would suspect a vacuum leak.

I suspect the following may be happening. As you slow down the butterfly closes and vacuum incteases to point where the leak occurs, more air goes in and so revs rise. The stepper then slowly corrects it and closes to get the revs down.

You set off and all is normal as the problem only occurs when throttle is fully closed.

Get a smoke test done to see if you can locate a vac leak