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Discussion Starter #1
Hi,

Back into Alfa ownership and need a little guidance regarding my 156 1.6 TSpark.

I've owned it for a few days and have I think poor fuel economy during my commute to work (8miles each way country roads). I've based this on the gauge shifting a lot rather than MPG readout, as it has used around 1/4 of the gauge in 32 miles, meaning I guess it'll do 128 miles to a tank!!!!
If you ask the MPG computer I did a test earlier:

16mile trip country roads this evening (Computer made it 10miles, no idea how?)
AVG speed on computer 20mph )must have been higher).
Average MPG 25.1.
Temp gauge made it to 65-68 and top rad hose was hot.

This was with the MAF unplugged, pretty much the same result as my 8 mile commute (to be fair I average 18mpg on the computer during that!!!)
Engine light is now on.

I have atleast 2x lambdas (2002 model).

Where should I start with this?
Clearly the computer isnt working properly but I think there is a fuel problem.one front wheel was warm but not so hot that you couldn't touch it etc.

Guess I need to check the air filter and inlet hoses before plugging into some obd reader?

Thanks
 

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There's a known problem with info centre getting confused between miles and Kms. Sounds like yours is doing that - 10 miles is roughly 16km. If you switch the units to metric you should find the km readout equals miles travelled. Your ave speed and mpg as indicated will be out currently as a result.
 

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Discussion Starter #3
Ah didn't think it could be as simple as that. Guess there isn't an easy fix unless I change the units...
Still think it's drinking too much fuel but I guess I need to monitor that or plug it in.
 

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Sounds like you need a new thermostat to.
 

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The OP may well need a thermostat but that isn't likely to have such a drastic affect on mpg.
If the OP is basing mpg on the bottom quarter of a tank then I wouldn't worry too much - the 156 can do that. I'd fill up run it til it gets to a quarter tank, refill and calculate mpg against mileage recorded Vs fuel used.
Your car will have 3 lambdas.
 

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Start with the thermostat, as above poster mentioned. If the car isnt running at 90c, the ecu will compensate and adjust the fuel distribution to rich burn, which in long run applies too much pressure on the catalytic converter and other parts of the engine, resulting in more expensive repairs.
 

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Discussion Starter #7
I am going to try real time mpg. I do suspect my MAF may be a bit dodgy as the mog figure was down at 18mpg before I unplugged it (up to 25) which I guess when you convert it makes a big difference? (I'm not clever enough to do the maths).
The test was from half tank to quarter tank.
Also how can I clear the engine.light or isn't it possible.aithout software?
 

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First of all, regarding fuel consumption you should make a proper calculation of how much petrol the car is consuming, based on how many miles it actually takes to empty one or two full tanks. You should never trust the display for measuring the actual consumption.
The display is not working like a “proper computer”, but basically shows readings based on the actual amount of gasoline being currently used.

You might want to save your lamba sensors until a proper (Alfa compatible) diagnostics program has actually confirmed problems with the sensors.
I don’t think you write whether the car is a pre- or a post facelift, but there are a substantial number of possible reasons for the engine lights being on – especially for the face lifted versions. E.g. ignition coil packs is a much more likely reason.

However, you might as well order a new thermostat - as many have already stated, - in case it stays around 60 degrees during a long drive in this weather:

https://www.alfaworkshop.co.uk/parts/156_Thermostat.shtml

https://www.alfaowner.com/Forum/eng...ow-to-change-a-thermostat-on-a-twinspark.html
 

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In mostly rural (but not highway) driving, my 147 2.0 litre TS was consistently displaying 8.8L/100km (32.1 mpg) "average consumption" (as indicated on the display, not 'properly' calculated which tends to be about 0.5L/100km worse than the computer display, i.e. the display is optimistic by about 0.5L/100km).

Some weeks ago I changed the two upstream O2 sensors (but not the one after the cat converter, which doesn't affect economy), and consumption immediately dropped to a steady indicated 8.4L/100km (33.6 mpg). O2 sensors can be quite bad but still not trigger a CEL (in fact can be utterly buggered and still not do so, as experience with my wifes' Saab proved...).

A week or so ago I changed the oil (old oil was very thinned out and runny like black hot water...) with a 20W/60 (Penrite), and indicated consumption has immediately dropped further to a consistent 7.6L/100km (37.2 mpg), an amazing improvement just from changing the oil, plus being noticably more powerful and quieter...

Your coolant temperature is quite low, this will mean that the AFR is always quite rich and so economy will suffer. You need a new thermostat. Thermostats for TS engines are stupidly expensive (considering what you would pay for a 'normal' thermostat for most other cars).

Recently I've discovered (not personally, from the internet) that it's possible to fit a Renault 5 thermostat into the TS upper radiator hose, for a much more reasonable cost. These thermostats open at a nominal 89°C, and have a 'drum' shaped body that can be jammed into the hose as near the engine as possible (a tight fit apparently, but it will squeeze in). The thermostat can then be held within the hose with a hose clamp (outside where the 'drum' fits inside the hose). Removing the guts of the original Alfa thermostat would probably be a good idea, though some say it works without doing this...

Regards,
John.
 

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If the MAF is unplugged then the ECU will be in 'open loop' mode, which will mean the engine is running too rich, and, will barely be able to sustain idling (may even not idle at all). My experience is also that the consumption display won't work with the MAF unplugged.

An excessively rich AFR will likely foul the spark pugs eventually, and cause misfires (perhaps make starting harder too). Excessively rich AFR will also tend to foul the O2 sensors, which will then tend to report a false lean condition to the ECU, which will respond by inappropriately enriching the AFR even more, which will further foul the sensors, which may then mistakenly report an even leaner AFR, etc...

My understanding is that ECUs can detect a broken heater circuit or a lack of data from the O2 sensors, and so generate a CEL (i.e. so bad that the sensor generates no signal at all or a broken signal circuit), but have no way of 'knowing' whether any data it is receiving is accurate or not, so 'garbage in / garbage out'...

Regards,
John.
 

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Discussion Starter #11
The MAF was unplugged to see if it positively improved MPG but as established the computer trip is misreading (kmh mph).

Commute to work complete, here's what I did:

Switched units to KMH and consumption to KMH/L (not 100L).
Approx 10mile journey - reader states 10kmh. Bang on.
Consumption 9.2KM/L which we assume is MPL = 41mpg? No other traffic, 40-60 crusing all the way so I suppose there is a chance it could be that high.
Any thoughts?

Also noted temp guage barely moved so Thermostat (although it's probably just the sender unit) needs replacement.
 

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The sender units are pretty reliable it's usually the thermostat itself which fails open. If replacing avoid Circoli as a brand. That mpg seems about right on a 1.6 at those speeds. If you can do a motorway run at 70 I'd expect that to drop off to maybe 35ish.
 

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I don't think there has been a thread where the thermostat was not been attributable for poor fuel economy (CF3 and later engines).

Circoli? Just avoid Euro Car Parts as you'll be paying over the odds.

OE Behr comes with a new sensor.

Top radiator being hot is no indicator of thermostat condition.
When engine is warming up, the heater hoses should become fully hot before the radiator top hose starts to become warm.

I could set my watch by how often a thermostat thread comes along. I'm surprised it's not a sticky.
 

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There is a sticky but:
1. Its not actually correct.
2. Too many words.
3. There is not link about fuel consumption. It assumes the thermostat is already suspected.

I don't like criticising those who have taken the time to help other but I think things could be improved.
 
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