JMC 0 Posted January 15, 2008 I've had a problem with my G60 recently whereby my mpg has gone down and it feels 'boggy' in the mid range. For instance a journey which I do regularly and used to get 30mpg I now get 27. Recently I've changed the front brakes (but they are not binding - checked that), had the map tweaked (bit it didn't seem to start at exactly the same time), and it has been a few years since the charger was serviced. I read somewhere that a failing blue temp sender can affect mpg - is the the case? Also if it is the case if there a way to test it to see if it is functioning properly (as well as the unplug it and watch for the revs dropping?)? Any advice would be great folks. Quote Share this post Link to post Share on other sites
Kevin Bacon 5 Posted January 15, 2008 I think for the cost of a new sensor, might be worth just sticking a new one in and see if it makes a difference? Have you got a Bentley? It should say in there what the resistance of the sensor should be at certain temps. Quote Share this post Link to post Share on other sites
Supercharged 2 Posted January 15, 2008 Yeah - resistance increases with age so it under-reads meaning the fuel enrichment map will run for longer... Could be the above tho but just becuase of the weather - mine is taking 10 mins driving before the coolant and oil hit 90... Quote Share this post Link to post Share on other sites
JMC 0 Posted January 15, 2008 Yeah Kev, I have a Bentley, will check in there (serves me right for not checking there first, doh). Thanks Supercharged, I thought I'd read somewhere that they degraded over time, so though it best to ask here :D Don't think it's the weather though, it has been quite a marked difference, and it didn't occur last year at this time. Quote Share this post Link to post Share on other sites
JMC 0 Posted January 16, 2008 Well, the more I look into this the more it seems to be temp dependant. Do my normal journey cold - 26mpg, do it with the engine hot 29mpg. And I've tried doing that half a dozen times, so it's not just a one off. Looks like blue temp sender is the first and easiest thing to try.. Don't suppose anyone knows the part no for one for a 92 G60 by any chance? Save me ordering one from VW, only to find when I get down there, they've ordered me in another headlamp :lol: Quote Share this post Link to post Share on other sites
plateletboy 0 Posted January 16, 2008 Do my normal journey cold - 26mpg, do it with the engine hot 29mpg. that is exactly what you would expect with a working blue coolant sensor.... cold engines use much more fuel, full stop... im getting far worse mpg at the moment because that big old VR6 block takes so much more energy to heat up from winter temps compared to summer pb Quote Share this post Link to post Share on other sites
JMC 0 Posted January 16, 2008 that is exactly what you would expect with a working blue coolant sensor.... cold engines use much more fuel, full stop... im getting far worse mpg at the moment because that big old VR6 block takes so much more energy to heat up from winter temps compared to summer pb So you think the sensor is working as it should be then? I was wondering if these things gradually fail (resiatnce as a function of temp gradually drifts), as I never had much of a difference before (it was always around 29mpg, cold or hot). Quote Share this post Link to post Share on other sites
plateletboy 0 Posted January 17, 2008 the sensor could be failing, but i was just making the point that using an engine from cold always uses much more fuel than a warm engine... as people have suggested, its a cheap part so just change it, or if you've got vag com check the readings are 'sensible' in block measurments.. pb Quote Share this post Link to post Share on other sites
JMC 0 Posted January 17, 2008 the sensor could be failing, but i was just making the point that using an engine from cold always uses much more fuel than a warm engine... as people have suggested, its a cheap part so just change it, or if you've got vag com check the readings are 'sensible' in block measurments.. pb Cheers plateletboy, I thought I'd better check though as it didn't make sense to my little brain :D . VAG-COM doesn't really show anything on mine as it is the older system, however as you say I may as well just change it. VW here I come. Quote Share this post Link to post Share on other sites
plateletboy 0 Posted January 17, 2008 ive only got vag.com version 3.something and a 'dumb' cable, but can read engine values.... go to 'open engine module', select measuring blocks, and then using the little up and down arrows on the left hand side, change the different lines to 1,2,3,4,5, etc you'll soon see if it measures something or not... i think coolant is on the first one.... pb Quote Share this post Link to post Share on other sites
JMC 0 Posted January 17, 2008 Cheers pb, I'll try that when I get the chance... Quote Share this post Link to post Share on other sites
JMC 0 Posted January 19, 2008 Oh well, got a replacement blue temp sender today from VW. Doesn't look exactly the same as the old one (and couldn't find a part no on the old one). Fitted it though and the engine ran fine. Lets see if this does the job..... Quote Share this post Link to post Share on other sites
JMC 0 Posted January 23, 2008 Mmmmh, changed the blue temp sender, and now the fuel pressure switch (as that was leaking petrol - nice). Neither have had any effect on my MPG. How's this for a thought - the charger is nearing it's rebuild period, although boost pressure hasn't dropped appreciably. Could this be the cause? Quote Share this post Link to post Share on other sites
ProdigalSon 1 Posted February 4, 2008 Have you ever had the fuelling properly set using an exhaust gas analyser? Have you checked that the lambda is working properly? There are about 8 different factors in getting the ECU to fuel correctly, and there are 2 to start with! My fuelling had been set a bit rich (on the CO pot) since before I bought the car, but not too obvious. However, a failing lambda probe sent it over the edge into black smoke territory! Once it was set by Daz at G-Werks it was infinitely better, but by that time the cat had died from all the excess fuel :( One new cat and lambda later, it runs like a rocket, flew through MOT emissions, and I'm getting easy 30+mpg on my 10 mile commute (was doing 17mpg for the same run when it was bad - we measured an air/fuel ratio of 10:1 on throttle and 12:1 on idle! :shock: ) Quote Share this post Link to post Share on other sites
JMC 0 Posted February 4, 2008 Have you ever had the fuelling properly set using an exhaust gas analyser? Have you checked that the lambda is working properly? There are about 8 different factors in getting the ECU to fuel correctly, and there are 2 to start with! My fuelling had been set a bit rich (on the CO pot) since before I bought the car, but not too obvious. However, a failing lambda probe sent it over the edge into black smoke territory! Once it was set by Daz at G-Werks it was infinitely better, but by that time the cat had died from all the excess fuel :( One new cat and lambda later, it runs like a rocket, flew through MOT emissions, and I'm getting easy 30+mpg on my 10 mile commute (was doing 17mpg for the same run when it was bad - we measured an air/fuel ratio of 10:1 on throttle and 12:1 on idle! :shock: ) I spend far too much time at G-Werks (they are always glad to see the back of me :lol: ) and Darren does most of the work on my car. Fuelling was originally set on an exhaust gas analyser, and the lambda is fine (my AFR is showing he typical beahviour of a narrow band lambda probe). One thing I'm going to rule out next is the tweaked map - Steve from PSD has done my map and we tweaked it slighly last time I was down there. Wondering now if that was a tweak too far :lol: . Fingers crossed... Quote Share this post Link to post Share on other sites
ProdigalSon 1 Posted February 5, 2008 I spend far too much time at G-Werks (they are always glad to see the back of me :lol: ) and Darren does most of the work on my car. Fuelling was originally set on an exhaust gas analyser, and the lambda is fine (my AFR is showing he typical beahviour of a narrow band lambda probe). One thing I'm going to rule out next is the tweaked map - Steve from PSD has done my map and we tweaked it slighly last time I was down there. Wondering now if that was a tweak too far :lol: . Fingers crossed... OK, so it could be a map thing... Doesn't sound bad enough to be a 'limp home' state, otherwise I would advise to check the voltages/earths... *refers to useful ECU pics* :wink: 2.8l 24v Climatronic system.pdfpg_0010.jpg[/attachment:2nwpqc9a]pg_0011.jpg[/attachment:2nwpqc9a] Quote Share this post Link to post Share on other sites
ProdigalSon 1 Posted February 5, 2008 Also, have you disturbed the knock sensor? Sure it's torqued correctly? Just a wild stab in the dark! :lol: Quote Share this post Link to post Share on other sites
JMC 0 Posted February 5, 2008 Ooh, those are useful pics thanks. As for the knock sensor, it isn't something I've played with before, and try to be very careful around it as I know it is delicate. Fingers crossed putting the map back to what it was before will cure it... Quote Share this post Link to post Share on other sites
