audi a4 b6 1.8t not starting 90% of the time

darren green

Registered User
Nov 5, 2016
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i have scanned the car using torque app and it brought up AIT sensor and cam sensor as faulty so i replaced these and has made no difference to it starting checked the maf reading on idle once finally started it was reading 2.5 g/s on idle on the revs it went up to 15.0 g/s i believe this is the correct reading. i can hear the fuel pump priming as well. any other thoughts on this would be much appreciated.
have you checked the crank sensor. this will affect the starting of your car.
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hi neil thanks for the reply
not yet mate i was hoping to change it tomorrow just found it strange how it didnt bring it up on diagnostic.
Got vcds now still bringing up cam sensor and ait sensor also replaced crank sensor cleaned maf and map sensor still struggling to start after its warm also i re aligned the throttle body
It won't run properly until you have dealt with the remaining codes that you have. The cam sensor and air inet temp sensor are on the same part of the loom (obviously) can you follow the loom from the sensors and check for any damage as far as you can. Also try disconnecting the sensors and give the connections of the sensor and the connector a good spray of contact cleaner or WD 40, you might as well clean the IAT as they're quite bad for getting covered in oil vapours, clear the codes and see if they come back.
hi calum thanks for the reply
i have cleaned the sensors and the connections with contact cleaner and cleared codes no difference. looks like il have to strip the cables like you said and check for contact through bare wires etc.
you dont happen to know which numbers the cables run to on the ecu block connector by any chance?
thanks darren
I'm sorry, I don't know which numbers they run to. Have you checked the throttle body? They can cause problems if dirty I know you did tba but if it dirty/ sticky it won't help.
just a quick update
i found a thread linked to the AIT sensor about the connector block on the AIT being wrongly connected to the MAP thermostat sensor, basically the wrong way round. it only occurred to me then as this might be the issue as the previous owner said he had changed the thermostat so he must have got them the wrong way round on re install. so i swapped the cables round cleared the codes and the car started up 1st time and every time previous. the cam fault code has not re appeared either so happy days on that. will double check everything in the morning.
thanks again guys for the input / help greatly appreciated. :)
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That was a good result, chances of finding that are slim. I'm surprised that the IAT connector reached as far, glad you have got it sorted at least it was easy enough to switch the connectors round.
I don't understand how previous owner mixed them up?
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Thanks guys yeah I'm surprised aswell but yeah it did. the cable was was pretty tight tbh I don't understand either.
But that's that sorted now on to the next issue I'm loosing boost after 2000rpm I think I might have a vacancy leak I'm going to check the dv