Air Temp Sensor, '95 Cali 1100i

[Dunders]

Hi, Folks,

I recently picked up a ’95 Cali 1100i.  Like most Guzzis of this age, it’s had some owners (and shops.I fear) that don’t know what they’ve got, and the fuelling is in a horrendous state.  Over 60 it vibrates like a bag of battery-powered vibrational toys…..  And drinks petrol like a stag party drinks JaegerBombs.

I’m new to EFI, but after research I downloaded GuzziDiag, and bought the Lonelec link (most excellent service, btw).  I had a quick look at GuzziDiag before I had to come away on holiday, and discovered that the Intake Air Temp sensor is ‘short to Vcc’.  Vcc is the supply voltage?  Sensor temp is shown as -48C, so that may account for excessive fuel consumption?

I’m guessing that the IATS needs replacing, and have ordered one for when I get back.

Qs: 

Where is the IATS located?  The best I have gleaned from the manuals I have/have found of the Net is that it’s ‘upstream of the throttle bodies’.

How critical is the Fuel Mix reading?  I have no access to a sensor/exhaust probe.  Living in the UK I guess I can get away with a out-of-spec reading, but will this affect the bike’s running?
 
Thanks in advance for any help!

Paul


BTW:  I’m using the Lonelec/GuzziDiag kit with a MacBook Air.  Works out of the box.

[Cliff]

The temp sensors are like a resistor to ground. So you don't have a short to Vcc, you have an open circuit to ground.

[Kiwi Dave]

Where is the IATS located?  The best I have gleaned from the manuals I have/have found of the Net is that it�s �upstream of the throttle bodies�.

From memory, there's two of these sensors.  One is attached to one of the valve covers, and this provides information about the oil temperature.  Another identical one I think is somewhere close to the airbox under the tank.

[Dharma Bum]

I know nothing about guzzi diagnosis but I do remember years ago (2001)when the dealer I bought my '96 Cali  from hooked it up to his laptop aND determined my air temp sensor to be bad.  Before he ordered a replacent he checked some other bikes in the shop and they all indicated bad air sensors.  Don't know if this applies to the problem at hand or not.

[fotoguzzi]

Not sure how much Guzzidiag can help on that '95.. but your symptoms sound like the TPS needs to be reset..
get the FI supplement from thisoldtractor.com
the oil and air temp sensors are a joke and were sourced for price.. why would you use an air sensor to read oil temp? located in the valve cover not in the oil?
TPS adjustment is very finicky but bring the Mv back to near good and it should be fine..

OH, the p8 CPU has a dial on the side under a plug.. if someone messed with that IT COULD BE THE WHOLE PROBLEM.  it's a idle trim screw, don't turn too far either way or it will pop out of the thread and adjust no more. about 3 turns each way I remember..if you adjust it, it may take a few miles for the change to be noticed..

[Wayne Orwig]

The temp sensors are like a resistor to ground. So you don't have a short to Vcc, you have an open circuit to ground.

:1:

It is very likely to be an OPEN, and there is likely a simple internal pullup to VCC.

[Kiwi_Roy]

This pretty much covers the early fuel injected guzzis

Sorry I couldn't find it, will update tomorrow
Here you go,
http://www.dpguzzi.com/efiman.pdf
note the resistance of the temperature sensors that should match the table on page 12
Although this is for a P8 ECU it shares much in common with the 15M.

These are a standard thermistor available for a few cents. They measure 3,000 Ohms at 25 degrees C
Visshay NTCLE203E 3302 SBO 
Digikey part No BC2730-ND

[Dunders]

Thanks for the responses so far.  I'm away from home on GrandDad duty just now, and lack the connectivity for frequent replies.

Not sure how much Guzzidiag can help on that '95.. but your symptoms sound like the TPS needs to be reset..
get the FI supplement from thisoldtractor.com

GuzziDiag does read the P8 parameters, and recognises the Cali 1100i. It showed the IATS problem, which is why I'm chasing info. 

I did reset the TPS as a first job - the lower speed running is much smoother.  The high speed running was still awful, and the fuel consumption horrifying, hence my foray into GuzziDiag.

the oil and air temp sensors are a joke and were sourced for price.. why would you use an air sensor to read oil temp? located in the valve cover not in the oil?

These must be rhetorical questions :-)  This is Guzzi of which we speak!  :-))

OH, the p8 CPU has a dial on the side under a plug.. if someone messed with that IT COULD BE THE WHOLE PROBLEM.  it's a idle trim screw, don't turn too far either way or it will pop out of the thread and adjust no more. about 3 turns each way I remember..if you adjust it, it may take a few miles for the change to be noticed..

This looks untouched by the state of the seal, but I'll check it when I get back.

Thanks again for the input.

Paul

[Dunders]

:1:

It is very likely to be an OPEN, and there is likely a simple internal pullup to VCC.

Thanks OMG and Cliff.  I was quoting the GuzziDiag fault box.  From further reading it looks as though the open circuit is fooling the CPU into thinking the air intake is very cold, and therefore causing overfuelling.    I do hope the fix is as simple as replacing the sensor (though how they can charge so much for a NTC thermistor is beyond me!

Paul

[Dunders]

This pretty much covers the early fuel injected guzzis

Sorry I couldn't find it, will update tomorrow

Thanks, Roy.  I look forward to reading it!

Paul

[Wayne Orwig]

Thanks OMG and Cliff.  I was quoting the GuzziDiag fault box.  From further reading it looks as though the open circuit is fooling the CPU into thinking the air intake is very cold, and therefore causing overfuelling.    I do hope the fix is as simple as replacing the sensor (though how they can charge so much for a NTC thermistor is beyond me!

Paul

Take and ohmeter to it before you buy a new one.

[Cliff]

I do hope the fix is as simple as replacing the sensor (though how they can charge so much for a NTC thermistor is beyond me!
Paul

I doubt the sensor has failed. More likely it is a dirty connector or a broken wire. Some tracing with a continuity checker should quickly locate the problem.

[Dunders]

Hi, Folks,

Got back from GrandDad duties a couple of hours ago.  Motomecca had delivered a new sensor whilst I was away, so I set about the problem. 

Finding the sensor on the bike was the biggest problem: I had convinced myself that it would be in the airbox - not at all!  (worth getting into the airbox to give it a good clean, though).  No: the clue is in the title: *Intake* air temperature sensor….  It’s mounted to a bracket just in front of the RHS air intake ‘scoop’.  That was 15 minutes I’ll never get back…

I removed the original, and tested it: 4.5 MegOhms.  The new one read 3.5 kOhms. 

On with the new, connect up to GuzziDiag, turn on the ignition.  Turn OFF the ignition very quickly.  Not used to Fuel Injection: sprayed the bike with petrol.  Lesson learned!  Clean it off, replace the air filter and tank, connect everything up. Try again.

All is well!  The air temperature now reads the same as ambient.  It’s too late - and wet - to run the bike, but tomorrow I’ll double-check all the TPS/balancing/idle work I did last week and hopefully get a good test ride in.  Maybe I can afford the petrol for it now…!


Thanks to those of you who replied to the the thread, and to Roy who offered to supply a sensor.

Paul