Scratching My Head With Idle Issues

[skanny 0]

Fellas,

 

The car used to idle at 1400-1500 rpm when hot, would start fine on the key - i never noted what it idled at when cold because i just start it and drive off!

 

I also had an oil leak which i blamed on the filler pipe from the bottom of the tower to the bottom of the block - it had split.

 

Here is what i have done

 

Remove all breathers and check and pull through with a cloth soaked in brake cleaner.

 

Remove AFM and clean with brake cleaner

 

Remove Throttle body and clean with brake cleaner

 

Remove idle screw and polish until shiny

 

Remove SAD unit and clean with brake cleaner and liberally oil with WD40

Upon removing the SAD i connected 12V to it and the hole did not get any smaller

I checked resistance and i have approx 55 Ohms between the 2 terminals.

 

With the SAD unit bracket removed from the side of the head i tested the ECU coolant sensor, I got no reading on my multimeter and no continuity at all between the 2 pins on the temp sensor.

 

Put it all back together.

 

Wound the idle screw all the way in and then out 1 turn

Started the car from cold and it started ok and idled at 1500rpm

 

I let it tick over until the fan cut in and out, it was still at 1500rpm.

 

Squeezed the SAD hose and it did nothing to the revs.

 

Pulled the ECU coolant temp plug off the the engine cut out.........

Why does it do that if there is no continuity at the sensor anyway? I thought that by it having 100% resistance (i.e no connection) and apparently no continuity, what effect can it be having?

 

should there be a resistance reading between the 2 terminals on the temp sensor?

 

I then checked the resistance on my spare SAD unit and put 12V onto the pins to see it it would move and it didnt.

 

The resitance of the spare unit was very similar to the on i have fitted already but i thought its worth a shot so i fitted it.

 

Started it up and its still the same.

 

So with the engine hot as it is now i turned the idle screw to make it idle at 1000.

 

The big question is will it start in the morning when its cold................Answers on a postcard.

 

My guess is no - but maybe im being pessimistic.

 

Im also thinking that the Sad unit is not at fault as squeezing the hose had no effect.

 

Is it possible that i have my breathers connected wrongly and its drawing in excess air from somewhere

 

The breathers are as follows

 

1) SAD to air intake between AFM and Throttle body

2) Other side of SAD to the under side of the inlet Plenum / manifold

3) Bottom of oil filler tower to big righthand (viewed from the front) hole on the bottom of the block

4) Cam cover to the T outlet at the bottom of hose no 3

5) Left hand small hole at the bottom of the block to the small outlet on the side of the oil tower

6) filler cap small hose to the top of the throttle body bu the idle screw

7) larger filler cap pipe to the air intake between the AFM and the Throttle body.

 

Anyone in the know confirm if that is correct or not?

 

I cant understand how the SAD unit is supposed to allow extra air in when the engine is cold, where does this extra air come from? it all seems like a closed breather circuit to me, nothing vents to athmosphere nor can it draw fresh athmospheric air into it, therefor it is all metered air that hs passed through the AFM..........................isnt it?

 

I know there are a lot of questions there but my research has not allowed me to cmoe to any conclusions, it does not help when 'SAD' is too short a search command lol.

 

I eagerly await your comments!

 

Colin

[jackherer 543]

The SAD bypass air has to be metered so fuel can be injected to match, the SAD bypasses the throttle body as opposed to the AFM.

 

If its all working it should idle nice and high from cold, 1300-1500rpm, then drop back to the 1000 you set it to when warm.

[lagonda 42]

The SAD....don't expect the shutter to flick over when connected....the 12volts heats up a bimetal plate which gradually moves the shutter. Mine took 5 minutes to close, if that's any help.

 

The engine temp sensor.....you're probably using too low a setting on your ohmeter. My meter needle didn't move on "Low", but on "High", showed a resistance of 1800-2500 ohms (tested 3 sensors) at around 20°. Mine does the same...cuts out if you pull the sensor plug.

[skanny 0]

The SAD....don't expect the shutter to flick over when connected....the 12volts heats up a bimetal plate which gradually moves the shutter. Mine took 5 minutes to close, if that's any help.

 

The engine temp sensor.....you're probably using too low a setting on your ohmeter. My meter needle didn't move on "Low", but on "High", showed a resistance of 1800-2500 ohms (tested 3 sensors) at around 20°. Mine does the same...cuts out if you pull the sensor plug.

 

 

I know the theory behind the SAD working and i actually connected one up on the battery and forgot about it and left it overnight!

 

Was still open in the morning!

 

I hae just been out to it and it started on the kye, no need for the throttle pedal to be pressed, it hunted a bit for the first 20 seconds but then was ok.

 

Fingers crossed, im going to drive it to work now and see what it idles at when hot.

 

Will report back later!