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Discussion Starter #1
Hi guys, can anyone tell me what symptoms I could expect if the temp sensor is faulty ????
My car has always had an unusually high craving for fuel. The emissions test at the last 2 MOT's have ruled out the lambda probe (which I have replaced anyway when it was faulty).
My car seems a little "dead" at higher speed in higher gears. Less responsive than I would expect. Also no matter how I drive the car I always get about the same mpg.
Plugs, leads, air filter etc are all good and no fuel leaks.

I'm thinking this: the temp sensor is making the ECU think that the car needs less fuel (that's why my emissions are almost non-existent). At higher revs in higher gears, there is more risk of pinking (I think), so because the mixture is weak, the knock sensor is retarding the engine. It may be doing it in low gears but I don't notice. The increased fuel consumption could then be down to me having to use morepedal for longer to get to a certain speed/revs, if you see what I mean.

Any ideas please.....

Marlon
 

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It`s a possibility that it`s giving a wrong reading :confused:

Or it could be your thermostat opening sooner than it should or even stuck open which will make your engine run cooler than it should therefore the ECU would be increasing the amount of fuel :confused: which is what it does on cold start up

Or maybe it`s just the way it is and you have to make it work harder because its an 8 valve :confused:

Dunno really :confused: think i`m starting to waffle so i`ll stop wink :D

Btw don`t all Alfa`s have a craving for fuel
 
M

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Discussion Starter #3
I replaced the stat when I bought the car and it's all fine temp wise. I'm suspecting the wrong reading scenario. It's about the only sensor I haven't replaced with a new one.

Oh yeah, whaddya mean because it's an 8 valve. We all know they are the engines to have.... wink :rolleyes:

Marlon
 
J

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Discussion Starter #4
marlon i changes my temp senosr last week, now sweet as a nut (also changed the stat cos it was stuck open) I can get you a sensor for £10
 
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Discussion Starter #5
my temp. sensor is good (I tested it with multimeter) my thermostat doesnt closing enough, but sparks are nice brown colour. I also get same (and high) fuel consumption in the city and on open road.
 
J

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Discussion Starter #6
If your stat does not close enough, then the water will not get up toi temp quick enough and it wil run cool, which could coause higher fuel consumption
 
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Discussion Starter #7
I replace my water termo sensor and you can easily check it with multimeter... readings should be around 200 ohm when is cold...
 
M

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Discussion Starter #8
Thanks guys. Jack I may call on you !!!
What should the reading be when the engine/water is hot ???

Marlon
 
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Discussion Starter #9
I dont know what the readings should be but there is a thread on here somewhere where a kind chap with too much time plotted a graph of the sensor readings ohms v temperature. If you need a sensor give me a shout marlon
 
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Discussion Starter #10
Hi, i think values should be:
-10 oC 9100-9300 ohm
0 oC 5700-5900 ohm
20 oC 2400-2600 ohm
40 oC 1100-1300 ohm
60 oC 500-700 ohm
80 oC 300-400 ohm
100 oC 150-200 ohm

temporary you could stick 175 ohm resistor instead of sensor and see how it goes...
 

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from the Manual the readings sholud be
40c = 900 - 1400 ohms
60c = 470 - 500 ohms
80c = 235 - 300 ohms
100c= 135 -165 ohms
120c= 80 - 100 ohms
hope this helps wink
 
M

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Discussion Starter #12
Thanks guys, I'll check for both sets of figures. Maybe the 8v and 16v have different values. Need to get a new meter though, just realised my cheapo thing doesn't give ohms, just a circuit test which is scaled in volts.
Bloody skinflint !!!!

Marlon
 
M

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Discussion Starter #13
I just replaced the air flow sensor with one I had in the shed (I actually have 3).
I think it might have something to do with this as now the car seems to pull like hell. Sounds a bit smoother and has a bit more of a rasp, in fact there is quite a noticeable difference in engine note. The AFM also has the air temp sensor in it I think (on the 8v and V6). Maybe that is what was causing my probs. I'll wait and see what the mpg is like.

Marlon
 
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Discussion Starter #14
thats right AFM have air temp sensor in it, it is like small wire inside but I dont know how this can be dead..I read somwhere that resistance of air temp sensor and water temp sensor should be about same so check it....
 
M

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Discussion Starter #15
Can someone with a parts CD handy get the part number for the 8v water temp sensor please. Also could you check if it's the same part for the 16v too.
My parts CD is still boxed up somewhere after moving house.

Cheers, Marlon
 
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Discussion Starter #16
Ok, there's one on the thermostat which I guess is the right one.......60800167 looks like its shared with everything except the 155 16v (perhaps the V6 engines?)

Price is £27.50

wrinx
 
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Discussion Starter #17
here is number from my previous water temp sensor 0 280 130 026 my car is 1,7 8v

cheers
 
M

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Discussion Starter #19
Well the AFM change didn't do anything. Still was only getting about 250-260 miles on a full tank. My daily drive which is A road/motorway mostly means I should get much more.

Luckily my local motor factors got me a temp sensor for £14.10.

All the aftermarket suppliers only list one replacement for all the 155's. This part is a direct replacement for all the Alfa part numbers (the guy showed me the catalogues which actually stated this)
Will have to see if mpg improves. I've just done 5 miles since changing it. It is a different car !!!!

The car now ticks over about 150rpm less.
When I rev the car, the revs drop smoothly (used to stutter on the way down like it was trying to burn off fuel).
The flat spot at low revs when pulling away hard seems to have dissapeared.

Overall the car feels much smoother on the road. I seemed to be able to wheelspin out of every junction easily. Before I had to make an effort to spin the boots.
The low throbbing rumble I got when driving at town speeds has turned to more of a typical "Old Alfa" rasp. I remember this sound from my Dads old Guiletta.

Like I say, let's hope the mpg improves as I'm starting to get a bit disheartened about the amount of money this car is costing me to run daily.

M
 
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