low idle revs nearly to point of stalling...

Ok so I replaced 48mm plastic throttle body with modified 48mm alloy one.She drives wonderfully and response improvement is better than I actually expected but since changing (given I had a high idle issue 1800-2100 rpm before change) I now have a ridiculously low idle of 500-600 rpm and feels like car wants to stall.I've been through iacv reset and I checked the two smaller pipes that push on to the tb and they both seem on properly etc.The butterfly and spindle and throttle all operate and look good (I didn't deform edges or anything).Is it air flow that's the issue? Or could it be something after the tb that's not quite right?

With the engine hot and the iacv disconnected, what is the idle speed?

You may need to adjust the base idle screw slightly. That is the screw that controls the rest position of the throttle quadrant.

Have you squirted some carb cleaner thtough the IACV? If that doesnt work you may have to change it. Its the other end of one of thse pipes held on to the inlet manifold with 4 cross heads. May be a how to on here.
The ECU drives it to controll ifle speed.

David Aiketgate wrote: With the engine hot and the iacv disconnected, what is the idle speed?

You may need to adjust the base idle screw slightly. That is the screw that controls the rest position of the throttle quadrant.

When you say disconnected, could I just remove the connecting pipe between iacv and tb?
And ok, hadn't thought about that screw actually... I'll try now.

Stan_B wrote: Have you squirted some carb cleaner thtough the IACV? If that doesnt work you may have to change it. Its the other end of one of thse pipes held on to the inlet manifold with 4 cross heads. May be a how to on here.
The ECU drives it to controll ifle speed.

Yes I cleaned the iacv a couple weeks back. Was in fact my first job on car and with new tools :broon:

I am hoping I don't need new one

Whiz wrote:

David Aiketgate wrote: With the engine hot and the iacv disconnected, what is the idle speed?

You may need to adjust the base idle screw slightly. That is the screw that controls the rest position of the throttle quadrant.

When you say disconnected, could I just remove the connecting pipe between iacv and tb?
And ok, hadn't thought about that screw actually... I'll try now.

No, you need to disconnect the electrical connector. it is doable (just) via the rear inspection aperture.If you take off the connecting tube the engine won't idle at all.

Try reverting to the TPS sensor from your old plastic throttle body - and obviously perform a TPS reset afterwards.

The throttle Position Sensor (TPS) is on the engine side of the thottle body, it mounts onto the end of the throttle shaft and held in by a couple of small screws.
It has an electrical connector, somwhat smaller than that on the IACV.

When I changed from 48mm to 52mm throttle body, I was warned to use the original 48mm TPS and not that fitted to the 52mm.
The "new" TPS could be defective or not have the right characteristics to match the fuel management computer in your ECU.

Have you reset the TPS before you go taking bits apart?

Turn the ignition on (but don't start). Press the throttle peddle to the floor and back again a number of times (can't remember the exact number, 10 is probably a safe bet) and turn the ignition off again. Start the engine and see if it helped.

Chris wrote: Have you reset the TPS before you go taking bits apart?

Whiz wrote: I've been through iacv reset

mogatrons wrote:

Chris wrote: Have you reset the TPS before you go taking bits apart?

Whiz wrote: I've been through iacv reset

I didn't see that bit! :oops:

Thanks for the ideas...
I have adjusted the little screw so it forces the throttle cable up a little so not idling as low but still hunting slightly. These 3 vids I recorded after screw adjustment...
Cold start...


Warm running engine...


Warm start after tps reset..