Knock and Inlet Air Temp sensor testing

[Rusty]

After some poor running in the heat at Inters, amongst other things (read toys) I'm looking at replacing both knock sensors and the IAT sensor to try and sort the car out. That's quite a bit of wedge if there's nothing wrong with them... So I'm looking at testing the sensors first to see if there is anything wrong with them! Seems sensible, right!

So, can someone please enlighten me as to the resistance to temperature scale on the IAT and the basic resistance fo the knock sensors so that I can at least have a look at them with a DVM and see if there's anything obviously wrong. I suppose I should have the car VAGCOM'd at some point too but the running problems have been around for a while and it was VAGCOM'd in mid April with no fauls found.

Cheers in advance for any help...

[Flat on my back]

You wont get a resistace off a knock sensor, its a piezo electric device. I can give you a digi picture of knock sensor o/p from a digi scope if that helps?

[Rusty]

OK, cheers. I could check it on a scope at work. Attach teh pic as a reference for others to see anyway.

Any ideas on the IAT? Must be in the Bentley or orig. Audi manual!

[Flat on my back]

AVO rather than a DVM and a hair dryer, might show something. Dont know the temp range for the IAT.

[audiman]

if you use vagcom you can see the inlet temp. Check it from cold and it should show about ambient. Easy test. If its a hesitation, have you checked for boost leaks??

[Rusty]

No boost leaks last time I checked it, no overboost protection for ages, just what feels like a complete retardation of timing. The boost stays at a solid 1.0bar and doesn't wildly fluctuate (I did a few 5th and 6th WOT tests down the motorway on the way home and could feel it messing about, no heat soak there!).

The car does seem to mess about a bit in traffic and this does not seem to be the experience of other members with standard cars. The 1/4 mile just made me realise that I should do some investigation the problem, shame I don't have VAGCOM.

I had always just accepted the poor hot weather running as heat soak but I'm sure that there is something else going on so soing to test stuff first.

[audiman]

knock sensors dont tend to go wrong and if they do you should get a fault code.

[s2dude]

vag com it

[S2central.net]

Yes - VAGCOM is a good way to test the IAT... I will try to dig out the electrical specs though - sure I have them somewhere. Heat soak is a real pain and the factory software is very conservative in this regard - playing things very safe with timing and boost levels at high air temp.

Knock sensors are indeed a pain to test - pictures off a scope would be good actually. I have a reference circuit for a knock detection device that I'd like to build one day - its cheap - just need the time - it works with our Bosch sensors and would give visual indication of knocks when they occur.

I'm planning on replacing mine along with IAT, lambda probe and shiny new coil packs one day to get back to full health. Expensive day thats gonna be

Paul

[Flat on my back]

Send me the circuit and i'll get one built up.

Pics tonite if it doesnt rain again!

[S2central.net]

Now theres an offer !

Let me see if I can dig it up.....


Paul

[S2central.net]

I love google - it was this one at megasquirt that caught my eye... Easy to build and cheap by the looks of things. I would do a two channel version - could easily be wired up to a spare lamp in the console or provide a digital output that could be monitored/recorded with an external ADC.

http://megasquirt.sourceforge.net/extra/knock.html

Paul

[220bhp]

I had poor running issues with my 3b,for a long time ,could'nt find the cause,did every thing to solve it,replaced n75, dump valve,boost hoses, maf, mfts, rear knock sensor,checked every thing I could with a multymeter,they all made a little differance, but the one that made a realey big differance was the front knock sensor. When I took it of the car the outer covering and the sensor covering just crumbled .

[Rusty]

Cheers 220bhp, I'm hoping that's the case with mine!

[Flat on my back]

S2central,

What sampling rate on that ADC you want? Now we're getting...too serious.

Thanks.