Speedometer 940

[98945lt]

I don't think I have that thing in my cat, but will take a look. I'm busy a couple of days now, I think a can check it out on wednesday or thursday.

[Laird Scooby]

Originally Posted by 98945lt

Hm. What is cold air intake and thermostatic valve?

A cold air intake is generally an aftermarket air filter with some ducting to provide cold air only to the engine. I picked one at random on the K&N website to link to as they don't appear to list the 940 (except for standard replacement filters) which turns out to be for a Celica. Shows the idea though :

https://www.knfilters.com/search/pro...x?prod=57-0324

As for the thermostatic air intake valve, Bob has kindly explained it very well with some great photos - thanks Bob!

Originally Posted by bob12

If you have one here are some pics of the one in my 745 (non-turbo). More often or not they get stuck in the open position so preventing hot air getting into the intake when warming up. I tried for a long while to find some in the UK. They are easy to get in the US. I eventually got mine from Skandix in Germany. Not cheap with the p&p. The original ones were made for Bosch by another German company Whaler (don't think I quite got the spelling right!).

PS - You have to be a bit brutal getting the plastic diverter assembly part with the air thermo in it separated from the main filter box. Depress the two holding nubs and then put the whole lot gently in a vice and thump away (easily) with a wooden drift and it will start to ease out.

They should provide partly heated air to the intake at all times, opening up completely to allow just cold air under full throttle for better performance/power. On normal driving this might cause problems though, especially in colder climates - it's possible the air intake temperature sensor (if you have one)is seeing extra cold air and increasing the idle speed to compensate.

This is only guesswork though.

[98945lt]

Have checked now and I don't have any of that parts in my car.

[98945lt]

Last week I took out the speedometer in my car to check the wire that signaled to the ECU and it was connected to the correct place. Also checked the line between speedometer and ecu with ohm meter and there was contact.
At the same time, I changed the control unit of the air conditioner just to check that there is nothing wrong with it. The car was still performing as before, with high idle speed after the engine was heated a little.
And I'm still as frustrated as before .....

[Laird Scooby]

Does the engine idle as normal if you switch the air conditioning off?

[98945lt]

There is no difference regardless of whether ac is on or off. It was really a shot in the bottom.

[98945lt]

Has now observed that the needle on the speedometer suddenly falls, last 4-5 mm before zero. Is this normal and could this be a possible source of error ?? Is there a possibility that the speedometer signal to the ECU is the "wrong type" signal?

[Laird Scooby]

It's rare that there is any signal from the speedo to the ECU except in automatics and then they need to be electronically controlled autos to need a speed input so the ECU can retard the ignition timing slightly for a split second at the moment of shifting gear to make the change smoother.

Usually the only time any ECU uses a signal from the speedo is for cruise control.

[98945lt]

I thougt the ecu used speedo signal for among other things like fuel cut over spesific rpm.

[Laird Scooby]

Why would it use the speedo? You could be in any gear and have different rpm yet the speedo would read the same.

What it actually uses to trigger things like fuel cut-off on over-run are the signal from the coil -ve and the throttle position switch.