Technical My stilo

[Deckchair5]

Does it hold steady 750 rpm tickover after a high rev kickdown or is it an "only just" tickover?

With a nice hot exhaust surge of exhaust gases the O2 sensors might have got up to better temp


Here's my O2 sensors, note O2 No.1 is swinging nicely between 0.1 and 0.8- no less - no more

The Post cat O2 No.2 is very happy and purring along between 0.1 min and 0.6 showing good combustion

Yours is wild and goes off the charts with 0v on both sensors here and up to 1v at times. That's totally out the window

So try disconnecting that No.1 O2 sensor just to eliminate it as it's output is vital for a good closed loop tickover

 

[Seraph]

ok, so i'm sat in my car, with my o2 bank 1 sensor disconnected.

i've got the fault code, but no engine management light...

the engine is ticking over at 1000rpm at the mo....but it is cold.

I can feel it doing it's little idle thing, it feels like it's shaking the car a bit. (if that makes sense
ok, so when i rev it up now, when it dips down it dips low... and bounces a bit. very nearly stalls...

 

[Deckchair5]

Ok take it for a little run and see if you've got a reasonable tickover afterwards.

 

[Seraph]

Just had the engine up to temp and it's been a stones throw from cutting out whenever i drop out of gear... and it felt less stable now, so i've just run it from standstill and the attached image is what happened when i rev up.

 

[Deckchair5]

Ok that looks pretty normal. Connect it all back up and your fault light should clear after a few starts. Bang in some new plugs tomorrow and do a normal run trace with a bit of tickover afterwards Both O2 sensors on top trace and rpm on bottom

My suspicions are on the No1 O2 sensor but it would be good to see some more data with certain good plugs. Just get the normal recommended plugs and nothing fancy and expensive

 

[Seraph]

ok, so the map sensor has been disconnected and the revs are really bouncing...
i'll show you idle.

 

[Deckchair5]

Yes the poor thing is getting lost now
MAP is obviously working

Connect it all up again, clear your fault codes, get some good plugs in there and see what happens

I forget now, has your car had the ECU/throttle body update?

 

[Seraph]

Yes the poor thing is getting lost now

i might add that was with o2 no 1 connected up again.

i'll get to halfords on my lunch break tomorrow and get the plugs/socket wrench.

 

[Deckchair5]

ok Post up another trace when you're done but suspicions are with the O2 No.1 sensor. Expensive bit of kit though so it would be nice to see some more of it's output. It look sluggish at the moment. Ought to be switching every few seconds

Have a look here http://www.lambdapower.co.uk/Diagnosis/Diagnostic_index.asp

 

[Seraph]

I forget now, has your car had the ECU/throttle body update?

pass and how would i go about getting that done?

 

[crazydave]

Awwwww chris is this still not sorted

 

[Seraph]

Awwwww chris is this still not sorted

yes mate it's still not sorted.

right then, so plugs all changed. here are the first set of readings.

 

[Deckchair5]

Hi Seraph
FIRST TRACE
looks good. You've just started it and you have hi tickover and very rich. That's normal and good

SECOND TRACE (the one on the right)
You're blipping the gas and it's holding tickover at close to 750rpm, O2 sensor is working properly from 0.1v to 0.8v when on tickover too

THIRD BOTTOM TRACE
It's holding tickover pretty well but the engine temp is still pretty low and
it's rich but that maybe because the engine isn;t up to temp yet.
Is that as high as the engine temp gets?
Do you have trouble with your coolant heating that you haven't mentioned like heater getting colder on long runs, taking a long time to warm up, needle hardly getting to N position?

It needs to be at normal running temp around 92 degrees

Fiat can tell if it's had an ecu/throttle body update by putting it on examiner

So how is the tickover, it looks better from what you show here.Never below 700rpm

Run it up to normal running temp and see what it feels/looks like. If it won't go up to normal running temperature or if it does but the engine temp sensor is saying cool then there's your problem

 

[Seraph]

Hi Seraph
FIRST TRACE
looks good. You've just started it and you have hi tickover and very rich. That's normal and good

SECOND TRACE (the one on the right)
You're blipping the gas and it's holding tickover at close to 750rpm, O2 sensor is working properly from 0.1v to 0.8v when on tickover too

THIRD BOTTOM TRACE
It's holding tickover pretty well but the engine temp is still pretty low and
it's rich but that maybe because the engine isn;t up to temp yet.
Is that as high as the engine temp gets?
Do you have trouble with your coolant heating that you haven't mentioned like heater getting colder on long runs, taking a long time to warm up, needle hardly getting to N position?

It needs to be at normal running temp around 92 degrees

Fiat can tell if it's had an ecu/throttle body update by putting it on examiner

So how is the tickover, it looks better from what you show here.Never below 700rpm

Run it up to normal running temp and see what it feels/looks like. If it won't go up to normal running temperature or if it does but the engine temp sensor is saying cool then there's your problem

hi, i stupidly didn't get the right readings at full temp, it's corrupted some of the date, so I'll have to give it another run, but essentially, all is not well.
it's still stalling and still dipping.

it's been doing something else too, which I forgot to mention, when it first starts up from cold invariably it will stall almost straight away.

at full running temp it's 93degrees, and it's running exactly as it was before I changed the plugs.

 

[Argonought]

Taking account of the history of the car (lots of work done) are you absolutely sure you don't have any leaks around the manifold/throttle body area due to parts being reassembled quickly :chin:

Just a thought.

 

[Rich]

This problem sounds like classic coolant sensor - not knowing how cold it is, and not giving the engine enough fuel to cope. However, it is reading 93 degrees.

You could try disconnecting the sensor, which should force the ECU into recovery mode (like a safety mode, the fan will stay on constantly too), and see how the engine runs then.

 

[Deckchair5]

It's showing eng temp of 37 on first two and then flatline at 68 degrees C on your recent traces

Do another couple of traces
Start up cold and monitor eng temp it should suddenly surge up as the thermostat opens. If it just slowly rises but takes ages or never gets to 93 degrees then suspect thermostat

Then do a trace with engine up to normal running temp if it'll get there. Should be there inside 5 mins. Blip gas and tickover

Plot both O2 sensors on top and rpm and eng temp on bottom

It really does look temp related

On this trace you did earlier both O2 sensors show a period when they are OFF, not just showing lean which would be 0.1v but completely switched off and unable to take any kind of oxygen reading. All you've done with the car or engine is started to slow down gently at that point

 

[Big Black Stilo]

is it a bad starter when its been hot?

My ibiza had a problem with a temp/coolant sensor which meant it would cut out changing gear or lack of power sometimes, and wouldnt start if it was hot.

On diagnostic equipment, the sensor was meant send a square wave (was no where near as sophistcated as this, was 8 years ago on a '96 car) but the wave was all over the place and far from a square wave, confusing the ECU and fueling the car incorrectly, or not at all

If it wouldnt start you have to disconnect the sensor, start it and put it back after 5 minutes.

 

[Seraph]

Right, so the results are in, Attached is a "at temp" section of a 5 minute graph...

if anyone wants to see the full thing, lemme know and i'll send the csv file for you to make your own graphs.

 

[Rich]

Ok, did you try disconnecting the sensor and seeing how it runs?

If the sensor is knackered and reporting a false temperature (e.g. the 80-odd degrees C yours is showing), the car's rev's will drop as there isn't enough fuel to keep the engine running, and will cause rev bouncing.