Hi a couple of annoying problems with my '98 a4 1.9tdi(ahu engine),
a couple of weeks ago the car developed a water leak which i traced to the plastic t pipe that houses the coolant temperature sensor(think thats the one, 4 wire job blue plug) there was a crack in it which i have now sealed up and the leak has gone. since then there have been a few noticeable issues, firstly the glow plug light on the dash now stays on for anywhere up to a minute before going out although the car will start as soon the fuel guage shows the level, also intermittently but twice in the last two days it has failed to start, it just turns over without firing, i suspect the glowplugs have failed but haven't had chance to check but i did check they are getting voltage.
the other issue is the idle is playing up, when the car does start the idle always goes up to 1100rpm whether the car is hot or cold, it's like the cold start is stuck on, when the car has been ran awhile say 10 minutes it settles back down to 900 rpm like it always used to be, but sometimes the enginehunts and the rpm fluctuates between 900-1000rpm, could this be to do with disturbing the cts or a unrelated problem thats happened by coincidence?
your help would be gratefully received
chris
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Both those issues are connected to the coolant temperature sensor.
The best way of fixing this would be to read the temp being sensed using the diagnostic tool, VAGCOM or similar, and then replace the sensor and/or check the wiring.
The sensor is cheap and easy to replace, so if you do not have access to VAGCOM, change it and see what happens.
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Alec is spot on, and although the job you've done of repairing the unit is good it's obviously living on borrowed time. The sensor is easy to replace and will probably need it again soon due to further leakage.
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Just a bit of lateral thinking. If it was leaking water, did it it get into the connector? Check that the pins aren't corroded/ high resistance or that a dried deposit is not shorting between any of the connections. Clean it all up spray with WD40 and plug unplug a few times to clean up the pins.
Could be cheaper than a temperature sensor.
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pmh (was peter)
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quick update, firstly the connector with the cts has been butchered the sensor goes in and is held happily in place by a circlip, but the wiring plug has been cut off and replaced with crimp connectors, checked it over and it looks to be ok connection wise.
secondly i took the input pipe off at the fuel filter and cranked it over and there was no diesel coming out, also can here the front fuel pump click on but not the rear, the rear pump seems to be covered in a bit of diesel for some reason, im suspecting the fuel pump at the rear has died although im struggling to understand why it would start last night albeit a bit of cranking required and then suddenly not work at all. i checked the manual and then the fuse box, book says no. 28 there is no fuse in no. 28 on my fuse box, put one in but it seems to have no affect.
could this all be related to the cts still? oh and the immob light goes out so im ruling out immob problems
cheers
chris
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also forgot to mention i tried measuring the voltage at the fuel pump and best it showed was 1.0volt does it turn off after so long or something as i did have to turn ignition on then run round car n stuff
chris
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