Passat TDI 1998 AFN Dies when cold

**Elvis the king** · 02-06-2008,05:42 PM

on the scanner the MAF % reading comes up 0.00000% all the time.
But the MAF has just had a new one fitted.

**Crasher** · 02-06-2008,06:29 PM

Once it is disconnected, the ECU defaults to using the air intake temperature and a base map to determine the engine temp, if the sensor tells the ECU it is -40°c it will fuel accordingly, its up to you anyway.

**snapdragon** · 02-06-2008,07:15 PM

If the -40c is given by the high resistance of a faulty sensor, then when disconnected, the same -40c or thereabouts will be given. They are cheap enough at ECP and GSF and are a common failure, so you may as well replace, they are practically a consumable.

**Elvis the king** · 04-06-2008,06:39 PM

Up Date !!
changed the temp sender no different.
Took the EGR valve off and cleaned it up checked that it works ok.
(Inlet manifold from the air in take on the intercooler was rather choked up) (needs stripping down really)
Still the same.

Any ideas folks???????

**Crasher** · 05-06-2008,01:08 PM

When it has cut out, you said it does not start easily again, does it sound odd, as if there is no compression? If you drive slower and don't rev it hard, I presume you can drive around this until it warms up and then it is OK?

**Elvis the king** · 05-06-2008,01:13 PM

Got it!
It sound odd, as if there is no compression.

**Crasher** · 05-06-2008,01:41 PM

Which grade of oil are you using?

**Elvis the king** · 05-06-2008,08:47 PM

15W/40.
you must be reading my mind.

I have just changed this evening to 10W/40semi synthetic

**Elvis the king** · 05-06-2008,08:48 PM

seems to run smoother.
but I haven't tried it from cold yet. ( I will try it tomorrow)

**Crasher** · 05-06-2008,11:04 PM

I think you are suffering from tappet pump up or jacking as it can be known, I have had this with the earlier TDI engines that use the direct drive pump in sump, rather than the later chain driven type. On the ones I have battled with this we tried a new oil pump, tappets and even dropping down to a 0w/50 oil and all we succeed in doing was reducing the warm up time it suffered from this problem and moving it up the rev band quite a lot but I could not completely cure it.