Skip the stepper?

[nicbowman]

Hi, here's an interesting queston ref pre-cat no cat. The stepper lets in more air when it opens, and when the stepper is shut the airscrew controls the minimum air in, which I presume is what happens at tickover, i.e stepper shuts air flow off completely, (apart fromteh air screw, presuming the airscrew is correctly set). I presume the stepper opens the air to increase the tickover on overrun, (for what ever reason?). My car (a 4.3) runw really well and clean, but is inclined to run at 1600 rpm for a few seconds before it ticks over. Why not take the stepper out and plug the hole?? What use is the darn thing?

Any ideas?


Nic

[mongoose]

The stepper is there to control idle speed only i think.They certainly run fine without them,i much prefer mine without,never get any idle variations anymore.

[GreenV8S]

The stepper controls the idle speed, and also lets 'extra' air in during overrun. The base idle should be set so that with the stepper completely closed the engine idles at around 500 rpm, this means the stepper motor is roughly in the middle of its travel under normal poerating conditions.

The stepper motor does improve the idle stability when it is working correctly, but given the amount of grief that people get when it plays up you have to wonder whether it is worth all the hassle. My new manifold doesn't have any stepper motor at all, means that the idle is rather slow and lumpy for the first few minutes from cold but no more bother with the idle speed mucking about after it has warmed up. If I ever get the scattered spark idle control working I think that would be even better.

>> Edited by GreenV8S on Sunday 19th March 18:49

[mongoose]

GreenV8S said:

If I ever get the scattered spark idle control working I think that would be even better.

you love playing with the Omex Peter dont you?

[nicbowman]

Cheers. Mongoose, how did you get rid of yours? Can you put a blanking plate over teh end and take the whole extension casting off?

Ta

Nic

[GreenV8S]

You *could* remove the housing and put a blanking plate over the hole, or just block the bypass hose, on the other hand why not just disconnect the plug and leave the rest of it alone? That also makes it dead easy to go back to standard if you don't like it.

[barreti]

mmmm, food for thought here guys.
My 4.3 revs like Nic describes and I've often wondered why. I put it down to reducing engine braking and therefore avoiding rear wheel lock-up when changing down.
I hate it though, it sounds like you've got your foot partially sat on the loud pedal like a numpty
I might try the suggestion of disconnecting it on the next outing and see how it drives.

[v8 racing]

the main reason the stepper is there is to control cold start warm up, when warm for sure you dont need it but when cold there is no other way of increasing the rpm

[nicbowman]

Cheers all, just confirming Green V8S, I presume remove the wiring plug when at the right tickover, then the stepper will be in the right position? This does not throw up a fault condition within the ECU?

Sounds like a good idea.

Ta

Nic