TVR RV8 Hotwire engines

[Jack Valiant]

Hi Guys.... bit of a long shot but I am after a replacement hotwire stepper motor connector for the 500 Gredge. Given the heat in the engine bay these connectors become brittle. So when I popped it off to replace the stepper motor recently the little plastic locking clip broke off. So wondered if anyone had one on an old loom etc that they would be willing to exchange for some beer tokens?

Pictures of the offending article below:





Thanks in advance

Chris

[keatsie]

I wouldn't worry about it, my has been broke since I had it without it..

[Jack Valiant]

Thanks but it is a issue as I have tracked intermittant idling problems to the plug security so needs to be done and would prefer to do it properly fella!

[mk1fan]

Chris,

How about soldering on some wires and moving a new waterproof plugto somewhere cooler?

[ElvisWedgely]

On mine, this system is disconnected. Not the electics, but the piping has been removed and the holes blocked. I bought the car like it and it starts and runs really well so I never bothered reconnecting it. Just takes a little longer to heat up in the morning but all those other running problems associated with the stepper motor are eliminated.

Tony. TCB.

[Jack Valiant]

mk1fan said:

Chris,

How about soldering on some wires and moving a new waterproof plug to somewhere cooler?

Yeah may do that if I cannot track down a direct replacement.

Tony - Thanks ..... Also tried running the car with the vacuum path blocked, the 500 Serp would not start well, so would prefer to do it properly as I know this is the issue. I have taped up the joint for now and its fine so will look out for a original replacement or alternative. Might try the Chim or Griff forums as well.

Chris

[adam quantrill]

Tie wrap around the body and another one from that round the wires and back again the other side should do the trick.

[wooly350i]

Hi Chris, I don't have a stepper motor on my 500 either; the ecu appears not to have wiring for it any way, perhaps this is why I get a hesitant idle when I first fire up but it soon settles down once heat is in there.
How does a stepper motor work might I ask?
John.

[Jack Valiant]

Hi John

The stepper motor, or idle control valve, is a mechanical device which opens and closes controlling air feed into the plenum at idle or low revs. If it becomes contaminated or fails then the engine idle can / will fluctuate. The number of steps or position of the valve is controlled by the 14CUX ECU. My understanding is that on the later serpentine engines it it needed. Mine certainly will not start easily or idle with it disabled in the closed position.

Chris

[wooly350i]

Hi Chris, I don't have a stepper motor on my 500 either; the ecu appears not to have wiring for it any way, perhaps this is why I get a hesitant idle when I first fire up but it soon settles down once heat is in there.
How does a stepper motor work might I ask?
John.

[Wedg1e]

wooly350i said:

Hi Chris, I don't have a stepper motor on my 500 either; the ecu appears not to have wiring for it any way, perhaps this is why I get a hesitant idle when I first fire up but it soon settles down once heat is in there.
How does a stepper motor work might I ask?
John.

Unlike a normal rotating motor, a stepper only rotates a fixed small amount per 'pulse' of current fed to it. So you can make it rotate a precise number of degrees by sending it a rapid pulse train; the controlling device then energises the multiple coils in the motor to create a 'holding' field so that it takes a lot of force to shift the motor from it's intended position - essentially CNC machines use this principle to give the precision of movement necessary, that's why they tend to make high-pitched noises when moving, it's the resonance of the motor coils being pulsed rapidly.
In the case of the Idle Stabilisation Valve the stepper positions a plunger or spool to admit varying amounts of air to more accurately control the mixture and - amongst other things - help stop the engine dying with the steering at full lock with PAS that you often see.
It's also why modern cars can pull away and go through the gears at idle without stalling; the ISV is managing to keep the engine at idle despite the load on it.
Unfortunately the plunger is susceptible to oil varnish and carbon build-up which the stepper can't overcome so it seizes and stops working. Usually a squirt of carb cleaner, isopropyl alcohol etc. will free it off and get it working again. Unlike a 'normal' motor a stepper won't fry if left powered in a stalled condition.

HTH