tdi misfire but no fault codes.

snips73

Member
Need some advice
A have had the tdi for about 4 years now and it has to be the most reliable car i have ever owned, the only non maintenance spend has been ARB bushes and a OS front spring in 60,000 miles
However over the summer the temp gauge stopped working or sometimes randomly showing normal operating temp. Not a big deal , car running fine.

However last few days car starts fine and runs ok but after about 5 mins of driving starts to cough and splutter.
Plugged the free version of vag com in and no fault codes are detected.
I also noticed that after 10-15 mins of idle the air through the blower is still cold and its taking an age to warm up during normal driving.
and now the cold weather is here

suspect the thermostat has let go and spends most of its time open, this would point to the temp gauge actually being correct and its cold....
Would that explain why vagcom is not picking anything up? Electrics and sensors are all ok

Any ideas.
Thanks
 
Hi snips73, welcome to the A2oc
Your 2001 TDi has a diesel fired Webasto auxiliary coolant heater (a bit like a miniature central heating bolier) and this aids warm up in temps below 5C. I suspect this is not working.
I also suspect the coolant temp sender unit has failed which is why the temp gauge (and possibly the Webasto) stopped working. See link for more info http://www.a2oc.net/forum/showthread.php?t=7776&highlight=temp+gauge+woes
Fuelling is influenced by coolant temp so maybe the engine ECU thinks the engine is still cold and overfuels it, leading to the rough running. Do you get any black smoke?
Freeware versions of VagCom often only read generic fault codes and may not give the full picture.

Cheers Spike
 
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Thanks Spike
however this morning it got worse , at least the ecu lights started working.
Plugged vagcom in and got the following.
any ideas


Control Module Part Number: 045 906 019 G
Component and/or Version: 1,4l R3 EDC 0000SG 1281
Software Coding: 00002
Work Shop Code: WSC 02138
Additional Info: WAUZZZ8ZZ1N050922 AUZ7Z0A1813642
1 Fault Found:
18075 - Valve for Pump-Jet: Cylinder 2 (N241): Electrical Malfunction
P1667 - 35-10 - - - Intermittent

Well it seems a few others have had this and its the injector harness.
http://www.a2oc.net/forum/showthread.php?t=8289&highlight=18075

I did a service a few weeks back so may be i knocked it, time to have a look
 
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The injector harness which causes the problem with symptoms similar to which you are describing lives under the rocker cover. So unless you had this off in the service it is unlikely you have disturbed it.

In my experience on the post you referenced the copper wire in the harness would appear to age, harsh environment really with heat, oil and vibration etc. The copper had gone almost black on the one i removed. Changing this was an instant cure.

Hope this proves to be the case as its really not that big a job. I would recommend you replace the rocker cover gasket along with the bolts too holding it down. After my own personal experience of the rocker cover leaking after id done it and also snapping a bolt off when torquing back up due to age the bolts were slightly corroded and one sheared at its thinnest section.

One other thing to check is the connector on the right hand side of the head which links the main engine loom into the injector harness. Worth a quick clean and some contact grease i did for a few weeks manage to cure the problem with this. As any increase in resistance in the wiring dirty contacts etc will add to this problem and tip it over the edge.

Gary
 
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