mx5cartalk.com

Cleaned the throttle body on my NB8B this morning and now when I come to a stop it idles at about 1500rpm for a few seconds before it drops down to 900rpm and stays there.

Is there an adjustment/setting I need to check

Well on mine the idle control screw is parallel to the throttle plate, and sits on top of the tb housing. I suspect there should be a rubber plug in the end of that hole, but isn't in mine.

There is also a stop screw that stops the piece the cable fits into the end of. I wouldn't play with that as it could affect the throttle position sensor for its idle settings...

Make any adjustments at operating temp.

And you need to short 2 pins in the diagnostics box before you adjust the base idle spped

Thanks guys

Tried to find how to adjust the base idle in the Mazda Worshop Manual
No mention of it anywhere

So I presume its Ten and Gnd that need to be shorted in the Diagnostic box then adjust the idle screw on the Throttle body

So I presume its Ten and Gnd that need to be shorted in the Diagnostic box then adjust the idle screw on the Throttle body

Yes

Its also possible that the throttle body cleaner you have used has removed the latex placed on the outer edge of the throttle butterfly, and you now have air getting past, and the effect of a partially opened throttle.

But in that case it shouldn't return back to normal idle speed hamish. When I cleaned the coating off my throttle body it wouldn't idle slower than 1200rpm even with the air bypass screw screwed all the way in.

You might like to make sure the throttle position sensor is plugged in correctly and the pins in the plug are making good contact KAM. That was the cause of my speradic fast idle problem. The car would idle at 1500rpm until I switched off the engine. When the engine was restarted it would idle at the correct speed. But your symptoms sound a bit different.

Just did mine on the weekend and a similiar problem. Was simply a sticky throttle.

Found the info in the Workshop Manual
Took the car for adrive last night to warm it up ready to make the adjustment.
During the warm up it came clear
Now when I stop it drops to about 900rpm immediately then after a few seconds drops to about 800/850rpm
Running beautifully now so will leave it alone and wait to see if the intermittent idle dip has gone.

Wasn't a sticky throttle as I had checked that on the weekend.
TPS was plugged in ok as I had put the original TPS back in after the clean (had a borrowed TPS before the clean trying to isolate the intermittent idle dip/power drop problem)
Didn't notice any latex on the butterfly before the clean just lots of black carbon build up.

just lots of black carbon build up

The latex was probably under the carbon. It's black too.

Garry wrote:

just lots of black carbon build up

The latex was probably under the carbon. It's black too.

In that case the cleaner has disolved the latex cause its all shiny and clean now (no black left)