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General Low MPG

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General Low MPG

Right, just got back from college and tested my sensor with a warm engine. I let the fan cut in then turned off the engine and tested it, it read 0.23.

I'm not sure where the 315 has come from, I'm getting confused about how you convert a 20k reading to a 2000k one:eek: I think its best if we only use the 20k setting.

So my readings are:

Cold 4.80
Hot 0.23

And your readings are:

Cold 5.90
Hot 0.28

Doesn't seem like my sensor is too far out really so maybe it isn't the problem. How would we go about testing the voltage? The sensor will need to be plugged in for us to do that so where would we connect the mulitmeter into?

As for the thermostat I reckon it might well be stuck open, carboard over the rad hasnt made much difference, temp is probably a little bit higher now but not much. Heater does take a while to get hot aswell. I'll get a new one and fit it at the weekend, it could do with a coolant change anyway, suppose I might aswell change the sensor at the same time, will completely rule it out then.
 
Good question :eek:
As the connector is sealed and we don't have a wiring dia to the ECU, only way would to mock-up a connector with male and female to allow for a reading to be taken (via some terminal block say)... but then fitting a new one is probably the easier option -esp. if time is short...
Just as a point of interest - as those links point out, a poor connection somewhere would increase the effective resistance as picked up by the ECU - so a voltage test would be more thorough than just testing the resistance of the sensor.
However, it would be better to check the other main avenue of the thermostat sticking or not seating properly first (rather than just fitting a new one of each - as then if it's cured, you won't know which of the two effected the cure!)
So, as your readings of the sensor are similar to mine, I would concentrate on the thermostat - fit a new one by all means but do test the old one to see if it is closing fully.
(y)

Ps Haynes always tell you to do things the hard way! The rad temp sw and the temp gauge sensor can both be changed without draining the system. Do it cold and leave expansion cap on - have the new one to hand ('fraid this don't work for the thermostat though as it fits a much bigger hole!)
 
Will change the termostat at the weekend then, the only thing is what could be causing the odd idle and spluttering? I've also noticed that if you rev the engine it takes it a second or two to return to idle rather than falling straight away. Any thoughts on what these problems could be if it isn't the temp sensor?
 
I think that as your hot readings are pretty much the same it's safe to say that the temp sensor is ok, so I agree with going for the t/stat first. If you do want to check the voltage to the temp sensor though you can spear one of the wires with a pin and connect to that.
It seems that the only way to solve these engine management problems is either to take it to a dealer for diagnosis, or start making educated guesses as to what component may be at fault and renew it, hoping that by the time we've solved the problem we've spent less than we would have if we'd taken the first option. I've had very little to do with the engine management systems on Pandas, or anything else for that matter, so would be interested to know if all the equipment and info is easily available to us to carry out this work ourselves? Anyone?
 
VmanC said:
I think that as your hot readings are pretty much the same it's safe to say that the temp sensor is ok, so I agree with going for the t/stat first. If you do want to check the voltage to the temp sensor though you can spear one of the wires with a pin and connect to that.
It seems that the only way to solve these engine management problems is either to take it to a dealer for diagnosis, or start making educated guesses as to what component may be at fault and renew it, hoping that by the time we've solved the problem we've spent less than we would have if we'd taken the first option. I've had very little to do with the engine management systems on Pandas, or anything else for that matter, so would be interested to know if all the equipment and info is easily available to us to carry out this work ourselves? Anyone?
Click to expand...

I know that with most new cars you can get the software and cables to be able to plug your own laptop in and do diagnosis, you can also buy code readers that display fualt codes aswell. I'm not sure if anything like this will work with a Panda? I thought as the injection systems on Pandas are so basic (especially the bosch system) whether there is much diagnostics available?

Back to the thermostat, I'm now not really sure, the heater was blowing fairly warm after a about a mile, it wasn't very hot but not cold either. I'm not sure whether to bother changing it or not.
 
Whether the engine is actually running cool (ie. thermostat) or whether the sender unit is telling the ECU incorrectly that it's running cool will still result in the same - the ECU 'deciding' that the engine needs more fuel...
Maybe we should turn our attention to the accuracy of the temp sensor for the temperature gauge (as you are basing your belief on the engine running cool on its reading..?)

My 4x4 is running cool - I've blanked off the rad but the temp gauge still seemed reluctant to go over 70° - now swapped the sender unit and the gauge IS reading higher, but still not what it should be at 80-90°. (Had I got an inj engine the manifold sensor that delivers info to the ECU would be telling it that I have a cool engine and this would certainly result in extra fuel delivery -
I suspected the manifold sensor because my CLX had similar problems to what you describe...
maybe all you need is some injector cleaner? This is something I did after changing my sensor (though the readings on my sensor were def. different to the new one)

If you want to up your MPG, you need to do something and unless you take it in to be looked at (expensive) you can only establish what it is by a process on elimination... (many garages would do this anyway!) maybe the thermostat has an intermittent fault?
:idea: Another basic test maybe would be to see how long it takes for the rad fan to sw on..? I got 3 here, all runners. But would the test be reliable with a standing car? A driven car would take for ever to get to temp as the coolant would be circulating freely with an open stat. When I took mine out of the 1000S altogether the gauge rarely got over 50, though I suspect that one that isn't seating correctly will probably only result in a 10° drop in running temp.
I think (as Vernon) that the thermostat has to be your first call (well 2nd if you dismiss the manifold sensor)
I got one for the 4x4 today £15 from local factor - hope to fit at weekend (or before if bad weather keeps me from working...)

Does the Panda ECU have a diagnostics plug? The EML seems very reluctant to come on with the Panda - with the Corsa it seems to be on most of the time! Only saying this because had trouble with Corsa but not Panda in this field...

Does yours sound lumpy on start-up btw? you could check plugs - see if it looks like its running rich...
 
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While I was at the scrappy getting a bit of hot air pipe yesterday, I also cut off the manifold sensor socket - so with the old sensor I can now make up a test connector with a bit of terminal block -(though a good idea (y) I don't think it would be a good to pierce the cable or for that matter use a Scotchblock connector as there may be some resistance or cable damage)
When I get time :rolleyes: I'll set this up on the CLX and read the voltage - perhaps a guide for this would be useful too :)
 
I'll change the thermostat this weekend if the weather is decent, it could probably do with a coolant change anyway, I wouldn't be surprised if its never been changed since it was new.

Went on a longer run today, about 25 miles, (I usually only do 5 miles journeys to college and work) engine was running at 90 on the guage, so I reckon without the cardboard over the rad it probably would have been around 80ish.

It doesnt run lumpy on start up aslong as you dont touch the throttle for about 10-15 seconds after start up, if you do it starts mis-firing.

To me it seems like the problem is with a sensor or something to do with the injection system because of the odd idle and spluttering as the thermostat wouldn't cause that, I'll eliminate the thermostat anyway.
 
Fitted a new thermostat this morning, i have tested the old one but it seems to be working fine. Started to open at around 83 and was fully open by about 87ish like it should.

I'll see what its like tomorrow, but it did seem to warm up quicker when it was idling than with the old one.

It only took about another 2 ltrs of coolant when I refilled it though. Didn't actually drain the radiator though as my Dad didn't want to take off the bottom hose incase it wouldn't seal again or the clips broke. Instead we took the top hose off and flushed it through that way, so there is probably still alot of old coolant left but it seemed clean enough when it came out.
 
If you look at my guide on thermostat testing they (new and old) are stamped 87 and 88 - so yours opening at 83 may indicate it opening too soon (though you have to ensure you are sampling the temperature of the water and not the bottom of the pan.
Changing stat on mine doesn't seem to have made any difference... :eek: (didn't appear anything wrong with the old one either but I didn't have time to test 'em together this time...)
Hopefully yours will run better - hope you get a result (y)
 
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