Help needed - is this a real error in air temp?

[blackfish]

Hi,

Having hooked up to the ECU on a '53 Punto, the main error shown was engine temp sensor, fatal error. I has suspected this before because the cooling fan sometimes came on with the engine cold (ECU thinking the engine is too hot?). Had a clean around the connector and measured the resistance to 3.33k, which is about right for a cold engine, based on the spec. in the Haynes manual. Ran the prog again, started the engine (though this was a struggle, several attempts needed) and watched a graph of engine temperature as it warmed up. Went back round to the engine and realised I had not put the sensor connector back on yet! So how come the ECU was seeing a warming up when the temp sensor was not connected? (some sort of default action?) It is definitely the right connector; green in colour, LHS of inlet manifold, two pins with resistance measured as stated above. Anyway, reconnected it and tried again. Temperature continued to increase and steadied off at around 82 deg C.

Thinking that was OK, I decided to look at some other parameters because the engine still seems to be not right (struggling to start). The one that was glaringly incorrect was air temp, showing as 50 deg C. However, there is no error shown, probably because it's OK to have an air temperature this high if you happen to be in Death Valley, USA. Snag is, I am in th UK in March and I'd say it was cool outside, no more than 10-12 deg C.

Do I have a problem Houston? I removed and inspected the manifold pressure/temp sensor and it looks OK but haven't tested it yet. I suppose two of the four pins go to the thermistor and I could check resistance but I don't have any reference to compare to.

Any ideas?

blackfish

[hanzs]

I think this is ok, I also have on my Stilo air temp. about 50 deg. C. on warm engine. Air is warmed by hot engine, so the temperature is higher then outside.

[EnIgMa]

The temparature it's ok.

I tested it on my grande punto last month, warm engine, with an elm327 device and i got about +38C where outside it was +6C

[blackfish]

But my air temperature is showing 50 degs before I start the engine. Car was cold, engine was cold, I was cold..... but ECU he say 50 degs (assuming the programme is converting the parameter correctly to degs C). When engine was up to normal temperature (coolant at 80+ degs C) air temperature still at 50 degs. No ECU errors reported so I don't think it's a default value in case the sensor signal is lost. I wouldn't expect the air to get warmed up too much as it is drawn through the air filter and down the throttle body, so I would expect to see it start off at ambient temp, say 10 degs C and warm up to say 20-30 degs C when the engine is running.

Anyway, I have another problem now. It started idling fast (up to 2000 rpm) and the idle stepper motor seemed stuck at value 138. Maybe it's time to strip the throttle body down. Still no ECU errors though.

I did start off with a fatal ECU error for coolant sensor (which may have been air in the system) so it gets more curious each day (coolant temp, air temp, idle stepper motor). Can still start it (with a struggle sometimes) and when it's hot it seems to run OK (though don't know whether ecomony or performance is suffering) so I'm not without transport and can continue to investigate.

blackfish

[hanzs]

blackfish: Air temp. sensor - you are right, on cold engine the value is near ambient temperature, not 50 deg. C.
The second problem - sorry no advice.

[Deckchair5]

Inlet air temp should be close to ambient on a cold start then rise rapidly after engine start. If it's showing 50degrees at cold start then there's a problem

Engine temp sensor won't put out a fault code for air in the coolant system, it's saying circuit problem so it's feedback voltage is out of limits so it's open circuit (most likely). Try cleaning the ETS contacts with electrical contact cleaner (not WD40 ) and you can check the ETS resistance at cold and hot engine to see if it'sacceptable.

Without ETS feedback then reliable engine starting will always be an issue, it will default to guessing the engine temp

[blackfish]

Engine coolant temp sensing seems OK now. I''ve cleaned the connections with solvent but would have liked to get into the socket contacts if I could figure out how to get it apart. I also noticed a gurgling noise and managed to bleed some air out so that wouldn't have been helping.

Combined air temp/pressure sensor was a bit contaminated with oil. Cleaned as best I could but temp still showing as 50 deg C. Will get a meter on it next.

Now I'm also suspecting idle valve and might take throttle body off and give it a clean out (idle valve and stepper motor are integral to throttle body). I suspect this because of the high and stuck values reported by Fiat ECU Scanner and the evidence of oil contamination in the throttle body (coming in from the breather - may be another sign of head gasket on its way).

blackfish

[Deckchair5]

If it's any help, my air intake temp shows exacly ambient before start up (10 degrees last time) so you can dismiss any problems with the ecuscan program, it does what it should so there is a fault somewhere on your air intake temp circuit

With the integral MAP and air intake temp sensor then being wet or covered in fuel won't do any harm as the sensor is totally enclosed in a solid gel to work in any environment. Getting the raw data out of your AIS would be a good idea and if you look here then you can deduce the approx range of output volts versus temp for Bosch MAPS

It's 5v supply in so I'd expect a rough range of 0.5 t0 4.5v

http://www.bosch.com.au/content/language1/html/4596.htm

click on the pdf downloads

Both your throttle valve and the MAP recieve 5v from your ecu so i'd check your 5v and earth supply to them