Too high revs when ticking over

[Thatch]

Dear Doctor,

In the warm weather, my 91 4.3BV Griff tends to start over revving when sat at junctions and the like. Normally it tends to idle at 1000 rpm, but when it gets a bit hot under the collar it sticks at about 1500.

Is this normal?

[kevinday]

No not normal, try the stepper motor?

[TeGriffic]

Normal in the sense that it's common. First port of call is the Stepper.

[simon.b]

Mine does this from time to time though when I think about it, it’s not happend since Joolz did my last service. I’d concur with the others and try the stepper motor first.

Cheers,

Simon.

[Thatch]

Thanks guys - sounds like the stepper then.

Oh, by the way, what's the stepper? where do i find it? and what do i do to it when i find it?

sorry - i'm not that technical, is this a job for the garage then?

cheers for your help so far!

[starmist]

It may just be your mixture. If it's running a bit rich at tickover, then as it gets hot, and the air gets hot, the mixture tends to lean off a bit, which will raise the revs. You will see the same effect by advancing your distributor.

[simon.b]

The stepper motor is a bypass valve in the air induction system. If you stand in front of the car with the bonnet up look to the left had side at back of the aluminium casting (plenum chamber) sitting on top of the engine. There you should see it, a black plastic bolt head approx. 1 inch across flats with a couple of wires coming out screwed into the casting.

If your used to messing with engines and stuff then just take this out and clean off the black crud, free up the plunger and put it all back, being careful not to over tighten.

It’s quite an easy job but best get your self a copy of the Bible (Steve Heaths book) if your not sure, it covers this and many other issues.

Do a search on the stepper it’s been talked about many times here and there may be a better more accurate description.

Cheers,

Simon.

[Thatch]

Thanks Simon - just the right amount of directiion and encouragement. I'll let you know how i get on

Cheers

[crankedup]

Always found that the dirty stepper on my Griff and previous wedgie's (ah happy days) showed itself by not ticking over at all, revs simply fell untill it cut out. Just thought I mention it

[HarryW]

Normally the stepper will hold it around 1500 if its playing up and its pretty much well covered throughout the Tiv forums. If its a lot higher than that I'd be tempted to make sure the throttle return spring/linkage/cable/accelerator is seating properly when your foot is off the gas as well.

harry

[Thatch]

Cleaned my stepper on Saturday, and has been fine ever since - Thanks everyone.

[Tom's dad]

I am a new (2weeks and 800m) owner of a bootiful 4.3 Griff, and am recently experiencing over revving problems at idle.
Having successfully removed the stepper and cleaned it thoroughly I note that their is very little movement in the plunger. What is the correct distance of travel. Is it in fractions of millimetre or more. Advise would be appreciated.

[Ballistic Banana]

Dont know for sure but would imagine it moves very little as it only controls the amount of air that bypasses the Throttle Butterfly.

Did it cure your Idle problem Graham.

If you havent got Steve Heaths Book yet i would advise to as it covers pretty much everything for the Griffith hence called "THE BIBLLE"(click)

I imagine that also prehaps cleaning the Throttle Butterfly also may help as can also get Carbon build up and stick, but be carefull as it is a little fragile.

Theres a section in The bible to that shows how to set the BASE IDLE SPEED


BB

[thatch]

When i cleaned my stepper motor there was very little movement at all. i put it down to the fact that it either needs to be at running temperature to move significantly, or the fact it was not connected electrically at the time.