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MG MGF Technical - Sensors
| Calling all you engine gurus! Can anyone tell me what effect on the engine fuelling/ignition timing each of the temperature sensors has? For instance, what tells the MEMS ECU to decrease the tickover rpm when the engine has warmed up? Is it the water temp sensor or is it the inlet air temp sensor? Or perhaps it's time related? If one were to magically cool the engine back down to overnight ambient would the tickover go back up again? Which sensor has the most effect on the fuelling? All questions...... Bruce |
| Bruce Caldwell |
| Weird, I was just looking up the location of the Intake Air Temperature (IAT) Sensor because I was thinking of cleaning the contacts to see if it helps my over fueling issues. Note to self: Need more tin foil to stop brain waves leaking out! |
| Steve Ratledge |
| I sense (pardon the pun) that I am getting under fuelling issues. My engine pinks slightly under load but only when warmed up to normal temp. Tried adjusting the sensor readings by adding resistance into the circuits but no affect on the pinking or tickover. Bruce |
| Bruce Caldwell |
| If you look in the RAVE manual it tells you what each sensor is used for, but I think you'll find that both are used. IIRC the air temp sensor is used to work out (with the MAP sensor) how dense the air is, the water temp sensor is used to decide how much to overfuel (like a choke) when cold. Pinking could be leaning out, but also might be old plugs - have you tried changing the plugs? |
| Will Munns |
| In the old days , I would have said you needed a de-coke, to remove the carbon deposits from around the valves and combustion chambers. But these days your not supposed to need this, unless you're using really crap petrol. sorry can't help. Mike |
| Mike (Mersea Office) |
| Is there any easy way to test if either of the sensors are faulty? |
| Steve Ratledge |
| Both sensors influence the ignition and fuel maps. The sensor that alters idle speed between 'cold' and 'warm' is the water temperature sensor. >>If one were to magically cool the engine back down to overnight ambient would the tickover go back up again? << Yes, it would. In fact, you can emulate this by placing a resistor in place of the water temperature - something with a suitably high resistance (the figures on Dieter's sensor pages should be a good guide). Temperature isn't the sole determinate of the mapping of course - the crank position sensor and the Manifold Absolute Pressure sensor are also critical - the MAP sensor influencing both fuelling and ignition advance under load and idle speed (throttle closed). If the temp sensors prove to be okay Bruce, then these are the sensors I'd check out next. |
| Rob Bell |
| Take it to MGR and connect it to the testbook? Check the resistance compared with Dieters 'sensor' page? Buy yourself an Emerald and plug it in ;-) |
| Will Munns |
| The Crank sensor cannot 'lie' like the others, it will either read correctly or not at all. |
| Will Munns |
| Steve, pop the sensors in a pot of boiling water and see how the resistance values change. I've done this on old water temp sensors - these have usually checked out okay, suggesting a problem with electrical contacts rather than with the sensor itself. |
| Rob Bell |
| >>The Crank sensor cannot 'lie' like the others<< Agreed - I'd look at the MAP sensor. |
| Rob Bell |
| Thought about changing the plugs but the problem has been there for some months and is not getting worse or better. So assume plugs are not the problem. Changed the water temp sensor to no avail. Inserted a variable resistor in line with the inlet air temp sensor. No change to the response or pinking at all. Increased the resistance right up to 1K in series but still no difference. Anyone know the resistance of the Inlet Air Temp sensor at ambient? Guess I might take it to a dealer to put his Testbook on it. Do Techspeed have a Testbook Rob? Bruce |
| Bruce Caldwell |
| Bruce B&G have a Testbook at Baldock. Only 58 miles excl M1. |
| JohnP |
| That's certainly an idea JohnP. Forgot about them. Thanks. Bruce |
| Bruce Caldwell |
| Hi Bruce, http://www.mgfcar.de/mems1.9/iat_2.33.jpg Had a measure when having had high idle troubles. 2.33 VDC at 8°C ambient temperature (ECU input) The manual says it works with similar ratings as the coolant temp sensor. This would mean app 2k Ohm ? I daubt. The only similar is IMO, it's an NTC (Thermistor) However, Testbook will know whether any sensor is damaged. It will not realise low deviations due to bad connections. (IMO) I only can assume i.e. 200Ohms is no failure for Testbook, but strange behavior of the engine. Another idea is, that testbook only can put *sensor failures* if the ECU switched to *fail save mode* ... cause a sensor got broken. I don't know. Just ideas. Still not finished and not confirmed diagram of the 5V powered sensors (MPI) http://www.mgfcar.de/sensor/sensors.jpg Good luck. Dieter |
| Dieter K. |
| Bruce, I'd go for B&G; TS sadly don't have testbook :o( MGOC in Cambridge also has Testbook I think? |
| Rob Bell |
| Thanks for that info Dieter. I will check the voltage at ambient and if nothing untoward found then I'll take it to my local dealer to run his Testbook over it. It may be that the sensor is open circuit in which case any resistance added into the circuit would make no difference at all. Perhaps the MEMS has a failsafe if the sensor goes o/c. Rob, B&G is a fair way for me in my six and a half hour lunch break. By the time I get there it will be time to get back. 6-10, 4:30-8. No holidays to come until next year. Shame TS don't have one. They are 5 miles away! cheers Bruce |
| Bruce Caldwell |
| Bruce - how far away from Wolverhampton are you? The MGF Centre also have a testbook. Other than that, then I guess you're in the hands of the local MGR dealer... |
| Rob Bell |
| How about we put a definitive list together of places other than Rover that have TestBooks? Starting with....... B&G, Baldock MGOC in Cambridge? Can anyone confirm? MGF Centre, Wolverhampton Any more? Tony |
| Tony |
| Good idea Tony, Dieter, I notice from the picture http://www.mgfcar.de/mems1.9/iat_2.33.jpg that the voltage is negative reading and it looks as if the red wire of your DMM is connected to Black/Green. Did you measure from chassis to Black/Green wire or from the Pink/Black wire which is Sensor Earth. If the voltage was actually a negative reading then maybe the Sensor Earth is really the Sensor Supply (5volts perhaps). Do you remember? Just checked the price of a new Inlet Air Temp sensor..£63 + vat! I think I'll be looking for a second hand one. cheers Bruce |
| Bruce Caldwell |
| Sorry Rob, Missed your question. About 25-30 miles from Wolverhampton. Good idea. Lot closer than B&G for me. Measured the voltage at ambient on my IAT sensor. 0.016 volts as opposed to 2.3 from Dieter, so possibly my sensor is faulty. Next step is to check the wiring which means hard top off. Got my hands on a second hand sensor already. cheers Bruce |
| Bruce Caldwell |
| <<Just checked the price of a new Inlet Air Temp sensor..£63 + vat! I think I'll be looking for a second hand one>> I think they were trying to sell me an MAP sensor. Bruce |
| Bruce Caldwell |
| <<How about we put a definitive list together of places other than Rover that have TestBooks?>> Good Idea, Any in Central Scotland.?? |
| John Dickson |
| Bruce, I recall. Picture isn't electric engineers quality like *applogy* :( (Get always shouted from Will due to this *ignorance* of the mechanical engineer ) :) Correction on the picture related measurement line colours. Please swap red and black colours of the instrument. Red is earth input. Black is plugged to plus at the digital meter. Bruce, I know you have the skills. :o) Please if you get the chance then try to enhence some missing values to the sensor circuit. http://www.mgfcar.de/sensor/sensors.jpg There's easy access to the engine bay sensor and the resistance of the IAT seansor is missing as well. I'm nearly sure all might have similar ambient temp resistance, but at least the adator housing is different at the front. For instance the engine bay fan sensor is none protected for quick action. IAT might be similar. Regards Dieter |
| Dieter K. |
| OK Dieter, I will send photo of my old IAT sensor. Also details of the resistances of the IAT and Engine Bay sensors. cheers Bruce |
| Bruce Caldwell |
| <B&G, Baldock <MGOC in Cambridge? Can anyone confirm? <MGF Centre, Wolverhampton MGOC in Cambridge advertise "MG Rover T4 Diagnostics" I presume that's the TestBook? Anyone confirm? Tony |
| Tony |
| Bruce, got them and included to the sensors site. "MG Rover T4 Diagnostics" Yup, T4 is the newest version (Laptop). Works for both, *our* old and aswell the new ECU with OBDII. They must make a new Testbook although cause the old Interface IC's got discontinued. (Xilincs) |
| Dieter K. |
| Bruce, don’t know it its too late (only just seen the thread) but I know of an independent MGR garage in Rugby who have a testbook and also one of PTP’s new super duper diagnostic computers. I used them once after my warning light came on and my dealer didn’t seem keen to look at it within a couple of weeks so tried this place and was very pleased with their service. IIRC they charge about £50 for a diagnostic. Let me know if you want their details. |
| Steve White |
| Steve, please post the details so we can build up a list of Testbook equipped specialists :o) |
| Rob Bell |
| Hi Steve, Yes please. I suspect it is the chaps from Banbury Rover who sent up as an independent when Banbury Rover moved to Oxford. I heard some time ago about them but don't know where they are. Would be very useful! I'm booked in at the MGF Centre where I guess the scenery is far better then most places, but for future use..... cheers Bruce |
| Bruce Caldwell |
| Banbury Rover moved to Oxford? That must be the new dealership up in Summertown then? They call themselves 'Alexance' now. No idea if they have testbook, though. Jamie |
| J Wakeham |
| OK here you go:- Rugby Car Care Centre 40 Sommers Rd, Rugby, Warwickshire CV22 7DH Tel: 01788 562162 They have been is business in Rugby for 18 odd years apparently, so don’t think it’s the Banbury lot. They also use MGR trained mechanics ;o) |
| Steve White |
| Thanks Steve, That's very useful to know. They are in the same road as my son's bodyshop business so it's very convenient. I heard a rumour some time ago that some of the Banbury Rover mechanics had moved to Rugby because they lived in this area and presumably didn't want to travel to Oxford everyday. Maybe they got jobs at the Rugby Car Care Centre? I will try them out sometime soon and report back. Or perhaps someone else on here has used them and can report on the quality of service. Thanks anyway Bruce |
| Bruce Caldwell |
| Bruce, I'd be interested to hear more about your sons bodyshop too, as I could be in the market for a new TF rear bumper soon. Victoria did a quick repair on mine to last me through the summer after I cracked it, but the damage is begining to re-appear and I would like to restore it to 'as new'. Last body shop I used in Rugby didn't seem to know the meaning of customer service and I wasn't overly impressed with the quality of thier work, so if I could find a reliable local firm to do it it would be great :oD |
| Steve White |
| Maidstone Sports Cars has.... "MSC is well equipped with the latest diagnostic and alignment equipment to be able to deal with the MGF. We also have the advantage of racing our 'MGF in the 'MGF' challenge (See Motorsport) where our success speaks for itself." www.maidstonesportscars.co.uk When I emailed asking just what they have, the answer was "We have the MGF code readers which are very good at finding faults". I have asked him to be more specific. Tony |
| Tony Thompson |
| Steve White, Email me at mgfinbraunston at aol dot com Bruce |
| Bruce Caldwell |
| Cheers Bruce, I'm off working up north tomorrow for a week, so I'll drop you a message when I get back :) Steve |
| Steve White |
| Anyone with testbook in Cheshire/manchester? |
| paul |
| Kernahan of Witney, Oxfordshire have the T4 diagnostics - see www.kernahan.co.uk Looks all the worls like a Rover Dealership, but the mg-rover website does not list them as such. |
| Tony |
| Quote from Summit MG, Maidenhead "I'm am sorry we do not have the rover test book but we do have the latest Sykes diagnostic that is almost identical to test book but better." Tony |
| Tony Thompson |
This thread was discussed between 25/10/2004 and 11/11/2004
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