Manifold intake air temperature sensor

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justin garthwaite

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Hi all. Just joined today, did a search and could not find my problem.
I have a 2004 Audi b6 Avant 2.5 Quattro and noticed she was starting really rough. Put her into a vag and she has an error code for the manifold intake air temperature sensor.. I have looked online and can't find any images pointing out where abouts this sensor is. I have tried my best to look around the engine but can't find anything. It's probably buried somewhere deep inside the engine.
If anyone knows where the sensor is could u please take a pic and show me please. Any help would be great and would be very much appreciated.
Many thanks.
Justy
 
I think there are only 2 sensors on the 2.5 intakes. 1st is the MAF (mass air flow) which is between the airbox and turbo. 2nd one is the MAP (manifold absolute pressure) which is on top of the left intercooler. The MAF picks up the temperature and air density whilst the MAP measures boost pressure. Check the flexibe air intake pipe between the airbox and turbo. These can split especially at the turbo end and they often throw up fault codes relating to the MAF. Rough starting could be any number of things. Coolant sensor, pump timing, partly clogged egr, faulty glow plugs etc.
 
abyrne153 said:
I think there are only 2 sensors on the 2.5 intakes. 1st is the MAF (mass air flow) which is between the airbox and turbo. 2nd one is the MAP (manifold absolute pressure) which is on top of the left intercooler. The MAF picks up the temperature and air density whilst the MAP measures boost pressure. Check the flexibe air intake pipe between the airbox and turbo. These can split especially at the turbo end and they often throw up fault codes relating to the MAF. Rough starting could be any number of things. Coolant sensor, pump timing, partly clogged egr, faulty glow plugs etc.
Click to expand...
I have since cleared the codes and none have came back on again.. but looking at another section of vag and noticed an error code for diesel injector + needle lift sensor. Would that cause my rough starting.. also should say when I start it first thing in the morning as well as it starting rough.. vibrations etc there is a lot of white smoke coming from exhaust. I let it tick over for a while turn off and start it again it runs fine.
 
The third injector on the right bank of the engine has a sensor built in. You can see the wire coming out from under the rocker cover. This sends signals to the injector pump and assists the ecu in providing correct injection timing. If the injector is faulty then essentially you can have rough running or poor performance as the pump timing won't be adjusted dynamically to suit the conditions. Check this isn't a wiring fault as a replacement injector is expensive. Cold starting problems with white / greyish smoke are more likely to be glow plug related or maybe the pump timing is not set correctly. The needle lift sensor doesn't really come into effect until the engine is running hence the reason why accurate pump timing is so important at startup.
 
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abyrne153 said:
The third injector on the right bank of the engine has a sensor built in. You can see the wire coming out from under the rocker cover. This sends signals to the injector pump and assists the ecu in providing correct injection timing. If the injector is faulty then essentially you can have rough running or poor performance as the pump timing won't be adjusted dynamically to suit the conditions. Check this isn't a wiring fault as a replacement injector is expensive. Cold starting problems with white / greyish smoke are more likely to be glow plug related or maybe the pump timing is not set correctly. The needle lift sensor doesn't really come into effect until the engine is running hence the reason why accurate pump timing is so important at startup.
Click to expand...
Thank you very much for the info.
So would it be best just to replace all the glow plugs? It's got 148k miles on her. How would I go about checking the wiring for the lifting needle?
How do I check the pump timing?
Sorry for the noobish questions but I'm a firm believer of "if I don't ask I won't learn" lol
I do appreciate your knowledge as there is not really a lot of info on the wonder web about this engine.
 
Check glow plugs with a multimeter. Pull off each plug cap and check the resistance of the plug centre to earth. Any that don't register or have a high resistance are likely faulty. Also ensure you have 12v at each plug when you switch on the ignition. Beware though the plugs are a pig to change and must be done with the engine hot. Most people soak the plugs in plus gas or similar for days before changing and even then they can snap in the head or strip threads and then you have real problems.

Check needle lift sensor by unclipping the wiring multi plug (just follow the wire back and you will, find it). Using a multimeter check the resistance between the 2 wires to the injector. It should be between 90 and 120 ohms when cold.

Pump timing is checked with a full version of vagcom in basic settings with the engine hot. There are other systems for checking using snap on solus pro etc but easiest with vagcom. If the timing is out of range you need to remove the top belt covers and loosen the 3 Allen bolts on the slotted pump drive sprocket on the left cam drive sprocket and rotate by tiny amounts right or left to advance or ****** the pump as necessary. Unless you are very handy with the spanners and have the diagnostic software both these jobs are best left to others. Have a look at some of adamss24 posts about these engines. His knowledge is incredible!
 
Last edited:
Manifold intake air temperature sensor is part of the MAP sensor. There is little point in measuring the temperature of the intake air at the MAF sensor as it bears little resemblance to that going into the engine after it has been through the turbo and intercooler. If you look in the end of the pickup on the MAP sensor you will see a small bead, that's the thermistor that measures intake temp.
If a glow plug doesn't want to come out leave it. They will start quite happily with several duff plugs so 1 or 2 duff ones is not a problem. You don't want to be removing cylinder heads to sort out issues after you have broken off glow plugs.
 
abyrne153 said:
Check glow plugs with a multimeter. Pull off each plug cap and check the resistance of the plug centre to earth. Any that don't register or have a high resistance are likely faulty. Also ensure you have 12v at each plug when you switch on the ignition. Beware though the plugs are a pig to change and must be done with the engine hot. Most people soak the plugs in plus gas or similar for days before changing and even then they can snap in the head or strip threads and then you have real problems.

Check needle lift sensor by unclipping the wiring multi plug (just follow the wire back and you will, find it). Using a multimeter check the resistance between the 2 wires to the injector. It should be between 90 and 120 ohms when cold.

Pump timing is checked with a full version of vagcom in basic settings with the engine hot. There are other systems for checking using snap on solus pro etc but easiest with vagcom. If the timing is out of range you need to remove the top belt covers and loosen the 3 Allen bolts on the slotted pump drive sprocket on the left cam drive sprocket and rotate by tiny amounts right or left to advance or ****** the pump as necessary. Unless you are very handy with the spanners and have the diagnostic software both these jobs are best left to others. Have a look at some of adamss24 posts about these engines. His knowledge is incredible!
Click to expand...
Mate your great.. thank you so much for the info..
sorry only getting back to you now but my back went and been on the old morphine lol.
Really appreciate your help and once my back is better I'll tackle the car with my tools and see what is going on.. have a great weekend.
And once again thanks.
 
desertstorm said:
Manifold intake air temperature sensor is part of the MAP sensor. There is little point in measuring the temperature of the intake air at the MAF sensor as it bears little resemblance to that going into the engine after it has been through the turbo and intercooler. If you look in the end of the pickup on the MAP sensor you will see a small bead, that's the thermistor that measures intake temp.
If a glow plug doesn't want to come out leave it. They will start quite happily with several duff plugs so 1 or 2 duff ones is not a problem. You don't want to be removing cylinder heads to sort out issues after you have broken off glow plugs.
Click to expand...
Nice one bud .. just googled that and seen that's the part I received. Hopefully my backs better soon and I can get this car going smooth.
Thanks for your help. I'll let you know how I get on.
Many thanks
 
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