Low-ish power and mpg
Discussion
Since I bought my Seat Leon 1.6TDI CR, I have been having varying fuel consumption results. I was told to adapt my driving style, and that has certain helped, however, I definitely think there is a problem with the car.
The problem I've noticed, is if I start the engine from cold, and let it get up to temperature, it NEVER reaches full efficiency, and it feels like an engine with 80BHP instead of 105BHP.
If I then stop for around 10-15 minutes, and turn the engine back on (whilst it's still warm), the MPG takes a massive jump up, especially on the live data display. The power also feels like it should. This is how I would have thought the car would perform all of the time.
I decided to do a test. I started the engine cold, got it up to temperature and went to the motorway nearby. I reset the trip when I reached 70mph, and stuck cruise control on. I did a 10 mile journey to the end of the motorway, made a note of the reading, and then did the exact same thing back up the other side (waiting until 70mph to reset the trip etc). I averaged the two readings. at 52.9mpg.
I then stopped the engine for 20 minutes, got a cup of tea etc. I then did the exact same test on the exact same bit of motorway. The average mpg this time around was 65.4mpg. A MASSIVE jump.
It's also returning on average 10mpg higher in urban driving when started warm, as opposed to being brought up to temperature and the trip reset
Do you have any idea what could be causing this? Someone on another forum said they noticed similar symptoms in a Mondeo with a faulty temperature sensor/thermostat. I've also read that it could be the MAF.
I have fully activated VAG COM, so if anyone could suggest anything I could be maybe monitor to take to SEAT, because, as usual, I'm just getting the old 'we're not having an issue when we drive it'. The car is under warranty so without an error code or some sort of evidence I don't know how far I'll get.
Thanks guys
The problem I've noticed, is if I start the engine from cold, and let it get up to temperature, it NEVER reaches full efficiency, and it feels like an engine with 80BHP instead of 105BHP.
If I then stop for around 10-15 minutes, and turn the engine back on (whilst it's still warm), the MPG takes a massive jump up, especially on the live data display. The power also feels like it should. This is how I would have thought the car would perform all of the time.
I decided to do a test. I started the engine cold, got it up to temperature and went to the motorway nearby. I reset the trip when I reached 70mph, and stuck cruise control on. I did a 10 mile journey to the end of the motorway, made a note of the reading, and then did the exact same thing back up the other side (waiting until 70mph to reset the trip etc). I averaged the two readings. at 52.9mpg.
I then stopped the engine for 20 minutes, got a cup of tea etc. I then did the exact same test on the exact same bit of motorway. The average mpg this time around was 65.4mpg. A MASSIVE jump.
It's also returning on average 10mpg higher in urban driving when started warm, as opposed to being brought up to temperature and the trip reset
Do you have any idea what could be causing this? Someone on another forum said they noticed similar symptoms in a Mondeo with a faulty temperature sensor/thermostat. I've also read that it could be the MAF.
I have fully activated VAG COM, so if anyone could suggest anything I could be maybe monitor to take to SEAT, because, as usual, I'm just getting the old 'we're not having an issue when we drive it'. The car is under warranty so without an error code or some sort of evidence I don't know how far I'll get.
Thanks guys
Thanks for the responses guys.
It takes around 5-6 miles to heat up on the morning run to work in current temperatures. About 3 1/2 miles of that is 50mph, the rest is normal urban driving in 30mph zones.
McSam, I have Vag Com so can take any readings, which readings would you suggest I take and then drive like you said? I'm sure it's not a placebo effect, but no harm in proving it. It's mostly around acceleration I feel the difference in power when I drive the car as I normally do, I.e accelerating to approx 2,500rpm and then changing gear (which drops me to about 1,500rpm in the next gear, any lower than that and the engine feels sluggish)
As for changing the thermostat, I can't, the car is under warranty and the reason im asking on here is so that I can try and nudge the dealer in the right direction, or if possible, obtain proof by collecting logs as stated above.
It's also strange in that turning it back on again immediately after turning off doesnt seem to cure the problem, it needs to sit for a few minutes at full temperature with the engine off.
I would have thought I was dodgy computer readings, but the loss of power and also the lack movement of the fuel gauge over long journeys when the engine has been restarted leads me to believe its genuine. My trip also underestimates by about 2mpg over a whole tank. I.e indicates 55mpg when hand calculated I've done 57mpg.
It takes around 5-6 miles to heat up on the morning run to work in current temperatures. About 3 1/2 miles of that is 50mph, the rest is normal urban driving in 30mph zones.
McSam, I have Vag Com so can take any readings, which readings would you suggest I take and then drive like you said? I'm sure it's not a placebo effect, but no harm in proving it. It's mostly around acceleration I feel the difference in power when I drive the car as I normally do, I.e accelerating to approx 2,500rpm and then changing gear (which drops me to about 1,500rpm in the next gear, any lower than that and the engine feels sluggish)
As for changing the thermostat, I can't, the car is under warranty and the reason im asking on here is so that I can try and nudge the dealer in the right direction, or if possible, obtain proof by collecting logs as stated above.
It's also strange in that turning it back on again immediately after turning off doesnt seem to cure the problem, it needs to sit for a few minutes at full temperature with the engine off.
I would have thought I was dodgy computer readings, but the loss of power and also the lack movement of the fuel gauge over long journeys when the engine has been restarted leads me to believe its genuine. My trip also underestimates by about 2mpg over a whole tank. I.e indicates 55mpg when hand calculated I've done 57mpg.
Edited by xreyuk on Thursday 14th June 12:13
Thanks for the information guys.
I didn't realise 5-6 miles was a long time to warm up, I'd been told that this was the norm by a few people on the Briskoda forums, and the guy from Seat told me his takes 15 minutes to warm up. I'm tempted to exaggerate when I next take it into Seat just to try and get them to change the thermostat, but as usual, no error code = no problem, although I've seen plenty of examples of a dodgy thermostat without error codes.
I have been measuring tanks brim to brim, and found that the trip computer under calculates by about 2 mpg, so I'm getting better mpg than it's indicating. Taking that into account, I doubt it's faulty when showing 52.4mpg for one journey, then 65mpg for the same journey.
I was wondering whether the gauge on the dash could be giving false information, I can monitor coolant temperature with vag com and do a start and see how it goes from there.
I can monitor a lot of stuff from Vag Com so anything that might help with the diagnosis of power can be logged. I've posted this in the VW marque forums to see if anyone looks there.
I didn't realise 5-6 miles was a long time to warm up, I'd been told that this was the norm by a few people on the Briskoda forums, and the guy from Seat told me his takes 15 minutes to warm up. I'm tempted to exaggerate when I next take it into Seat just to try and get them to change the thermostat, but as usual, no error code = no problem, although I've seen plenty of examples of a dodgy thermostat without error codes.
I have been measuring tanks brim to brim, and found that the trip computer under calculates by about 2 mpg, so I'm getting better mpg than it's indicating. Taking that into account, I doubt it's faulty when showing 52.4mpg for one journey, then 65mpg for the same journey.
I was wondering whether the gauge on the dash could be giving false information, I can monitor coolant temperature with vag com and do a start and see how it goes from there.
I can monitor a lot of stuff from Vag Com so anything that might help with the diagnosis of power can be logged. I've posted this in the VW marque forums to see if anyone looks there.
I believe the thermostat is around £20 from SEAT, but as stated above, I can't touch anything, the car is under warranty.
As for the DPF, yes I have one, but I drive mainly motorway miles, about 80% of 600 miles a week is motorway miles. Also this problem happens every time, regardless of how long the journey is, it is miles better after a restart.
As for the motorway test, as McSam said, all of the testing was done within the same hour, on the same stretch of the M58, and all the averages were taken over both directions, as obviously, one way can be downhill, the other uphill. When joining the motorway, I got up to a constant 70mph before leaving the slip road, and stuck the cruise control on to maintain consistency. I reset the trip computer as I crossed the slip road line, and took my reading as I left the motorway and crossed the slip road line again. I did the same coming back up the other side of the motorway.
On the 'warm-start' test, I did the same procedure as above, and the mpg was around 12-13mpg better. It's also incredibly noticeable around town. Starting cold and bringing up to temperature around town, is around 48mpg, but it's near 55-60mpg when starting with a warm engine.
As for the two people saying that the trip computer is counting the cold start period, and fuel running richer when cold, when the engine reaches temperature I restart the trip computer, all of my measurements have been done with a warm engine, as I understand a diesel engine isn't efficient until warm. No measurements have been done unless the engine is completely up to temperature, so this means that no cold engine driving is included.
With regards to the power issue, I understand there isn't going to much power and performance when shifting and dropping to 1,500 RPM, that was never my problem. My problem is that the car drives differently at those same RPM when the car is started warm, than when it is fully up to temperature after being cold. I don't think the car is sluggish in general, but I do think the power is different between the two scenarios.
@ Olivera - As stated before, the trip computer is accurate within 2mpg over a tankful. I don't get the chance to do a long enough motorway stint, get somewhere, not stop the engine and go back up the other way, and then do the same procedure again (but stopping the engine) so I can get an accurate hand calculation. If I do get the chance, I'll definitely do it, because it's more proof, but I find it hard that a trip computer that is accurate to 2mpg over a tankful, is 12mpg out on two motorway runs that are identical, or two town runs. The pattern is also consisetent, as I've noticed it over the past couple of months, every day. I've not just noticed it willy nilly, it's been happening pretty much since I had the car.
I am doing my best to explain my situation.
As for the DPF, yes I have one, but I drive mainly motorway miles, about 80% of 600 miles a week is motorway miles. Also this problem happens every time, regardless of how long the journey is, it is miles better after a restart.
As for the motorway test, as McSam said, all of the testing was done within the same hour, on the same stretch of the M58, and all the averages were taken over both directions, as obviously, one way can be downhill, the other uphill. When joining the motorway, I got up to a constant 70mph before leaving the slip road, and stuck the cruise control on to maintain consistency. I reset the trip computer as I crossed the slip road line, and took my reading as I left the motorway and crossed the slip road line again. I did the same coming back up the other side of the motorway.
On the 'warm-start' test, I did the same procedure as above, and the mpg was around 12-13mpg better. It's also incredibly noticeable around town. Starting cold and bringing up to temperature around town, is around 48mpg, but it's near 55-60mpg when starting with a warm engine.
As for the two people saying that the trip computer is counting the cold start period, and fuel running richer when cold, when the engine reaches temperature I restart the trip computer, all of my measurements have been done with a warm engine, as I understand a diesel engine isn't efficient until warm. No measurements have been done unless the engine is completely up to temperature, so this means that no cold engine driving is included.
With regards to the power issue, I understand there isn't going to much power and performance when shifting and dropping to 1,500 RPM, that was never my problem. My problem is that the car drives differently at those same RPM when the car is started warm, than when it is fully up to temperature after being cold. I don't think the car is sluggish in general, but I do think the power is different between the two scenarios.
@ Olivera - As stated before, the trip computer is accurate within 2mpg over a tankful. I don't get the chance to do a long enough motorway stint, get somewhere, not stop the engine and go back up the other way, and then do the same procedure again (but stopping the engine) so I can get an accurate hand calculation. If I do get the chance, I'll definitely do it, because it's more proof, but I find it hard that a trip computer that is accurate to 2mpg over a tankful, is 12mpg out on two motorway runs that are identical, or two town runs. The pattern is also consisetent, as I've noticed it over the past couple of months, every day. I've not just noticed it willy nilly, it's been happening pretty much since I had the car.
I am doing my best to explain my situation.
Edited by xreyuk on Thursday 14th June 20:46
Thanks, I'll make a log of the coolant temperature and anything else I think is relevant on next start up and see what happens.
I was thinking thermostat myself, but like I said, it doesn't appear to be a long warm up period. Hopefully they won't have to reset the ECU, but we'll see.
Any other recommendations would be greatly appreciated.
I was thinking thermostat myself, but like I said, it doesn't appear to be a long warm up period. Hopefully they won't have to reset the ECU, but we'll see.
Any other recommendations would be greatly appreciated.
Edited by xreyuk on Thursday 14th June 23:01
Locke said:
Sorry, I should maybe expand.
I'm not a mechanic but a thermostat malfunctioning on a car that age is quite rare, It wouldn't effect the power like you describe and although it would effect mpg I can't see it resulting in a 12mpg difference.
HTH.
Cheers, oh well, here's to hoping.I'm not a mechanic but a thermostat malfunctioning on a car that age is quite rare, It wouldn't effect the power like you describe and although it would effect mpg I can't see it resulting in a 12mpg difference.
HTH.
Any idea what else it could be? It has been suggested it could be the MAF, but I wouldn't have thought it was have affected it in this way.
Well, as usual.
Sods law kicked in today, and for the first time since I've owned the car, it behaved properly as soon as it got warm, from a cold start. It's never done this before, and it would happen when I went to log the information. I'll try doing another log over the next few days to get one of the bad startups. Hopefully though, that might have been the last I saw of it today.
Quick question, what temperatures should I be seeing? I saw the following:
Coolant Temp at Radiator outlet: 44deg
Coolant Temp: Went as high as 97deg, and then cooled a little to 93deg.
Oil Temp: Settled at around 89/90 deg.
That coolant temp seems a little bit high from what I've read on the internet?
Sods law kicked in today, and for the first time since I've owned the car, it behaved properly as soon as it got warm, from a cold start. It's never done this before, and it would happen when I went to log the information. I'll try doing another log over the next few days to get one of the bad startups. Hopefully though, that might have been the last I saw of it today.
Quick question, what temperatures should I be seeing? I saw the following:
Coolant Temp at Radiator outlet: 44deg
Coolant Temp: Went as high as 97deg, and then cooled a little to 93deg.
Oil Temp: Settled at around 89/90 deg.
That coolant temp seems a little bit high from what I've read on the internet?
McSam said:
Sounds reasonable to me. The thermostat probably opens around 88-90'C and it won't go much above that, but a peak of 97 and settling to 93 isn't anything to worry about, unless these engines are known for running very cold?
Here's hoping that's the end of it!
Hopefully so. I'm secretly hoping it's just decided to behave itself, it was even much better at high speed after a while, just after it had warmed up, it was poor though.Here's hoping that's the end of it!
However, I'll keep monitoring it, and if needs be over the next few days, do another test and possibly post on here.
Thanks for the responses.
Where I live, it's a 30 minute drive to the motorway, so the engine is definitely up to temperature.
Ironically, since I monitored a start up the other day, the car has actually warmed up correctly, I don't know why or how, it's probably sods law, but I"m goign to keep monitoring it.
Is the thermostat and coolant temperature sensor the same thing or different?
Is it really a cambelt off job to change the coolant temperature sensor? If so, I'll make sure I remember just to get it changed when the cambelt is off.
At the moment however, the car is under warranty, so it's anything goes.
Where I live, it's a 30 minute drive to the motorway, so the engine is definitely up to temperature.
Ironically, since I monitored a start up the other day, the car has actually warmed up correctly, I don't know why or how, it's probably sods law, but I"m goign to keep monitoring it.
Is the thermostat and coolant temperature sensor the same thing or different?
Is it really a cambelt off job to change the coolant temperature sensor? If so, I'll make sure I remember just to get it changed when the cambelt is off.
At the moment however, the car is under warranty, so it's anything goes.
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