Passat PD 130BHP Temp sender location?

[alba_tdi]

Hi,
I have a query that i hope someone can assist with.
My 01 Passat TDi has an intermittant misfire, it can go for days without a single misfire then you can get a day where it is missing frequently. The car has been hooked up to a Bosch diagnostic gizmo and the only fault found was a short circuit/dead short - temperature sensor. I am assuming this is on the coolant side.
I have found out from VW that the temperature sender is Part No 059919501A. I can't locate this anywhere, can anyone tell me where to find this sender, and secondly is the faulty sender going to cause a misfire?
By the way the temperature gauge is reading exactly 90 degrees C but the diagnostic check was showing the engine temp at only 74 degrees C.
Thanks.
alba_tdi
:mad:

[glynnd]

The ecu gathers info from the temp sender and the fuel temp sender and uses the info to supply the correct amount of fuel and boost etc along with other things such as injector pulse width. Wrong info when the engine is hot or cold can produce a misfire due to an over rich or weak mixture. I believe the engine coolant temp sender is located on the rear of the cylinder head on the left side looking at the car from the front.
Fuel temp sender is located in the fuel return line behind the oil filter housing.

:biglaugh:

[alba_tdi]

Cheers glynnd.
Thanks for the information. I have bought a new temperature sender and i will replace it and let you know if there is any improvement.

[alba_tdi]

New temperature sender fitted and the car's running worse than ever....
There is little power up to 2,500 RPM then the power is delivered but still not like what it used to be.
I have refitted the original sender and it is running better than with the replacement sensor, but still not what it was like.
Does anyone have any ideas or advice?
Thanks again.
alba_tdi.

[glynnd]

First try running the car with the air mass meter disconnected. If its not worse then the meter may be at fault.
Also try running the car with the fuel temp sensor disconnected. This can be found in the fuel return line just behind the oil filter housing. It has a green clip securing it.

:biglaugh:

[glynnd]

Could also be turbo boost control valve or split in vacuum pipes. The boost control valves have been known to fail giving poor performance

:biglaugh:

[alba_tdi]

Hi glynnd,
Thanks for all the assistance.
I have lifted the bonnet and found one of the vacuum pipes to the air filter box was disconnected, when the engine was running you could hear the air getting drawn in, i must have disturbed it when i was changing the sensor, i have refitted this pipe and the performance is perfect.
All i need to do now is refit the new sensor and start again.
I'll be doing that tomorrow and will let you know how i get on.
Hopefully the new sensor will work better this time.
Cheers again.
alba_tdi

[glynnd]

Glad you have sorted it!


:biglaugh:

[alba_tdi]

Wish i had your confidence!
All being well i will be a happy chappy tomorrow when i refit the new sensor and see if the misfire is cured.
:beerchug:

[alba_tdi]

New temperature sender fitted and misfire still there when engine reaches working temperature. Have tried disconnecting the MAF sensor and the car runs flat but still misfires but not as badly, also disconnected the fuel temp sender and this didn't help either.
I have been told that unless warning light is present when the car is misfiring a VW diagnostic check will not show a fault, does anyone know if this is correct? I was hoping i could drive the car with the diagnostic kit connected so when the car misfired it would be visible on the screen where the fault was.
Any suggestions would be greatly appreciated.
Thanks.
alba_tdi
:1zhelp:

[glynnd]

You will usually only get fault codes from components that have an electrical supply to them. Does the misfire occur when the car is cold too. The misfire is possibly a problem with the fuel injectors (number 3 is known to be a problem) as you are probably aware that there is no spark in a diesel engine. So i would suggest that a lean or over rich mixture would only cause a loss of power not really a misfire. Hope you get ot sorted as from my experience vw repais are not particularly cheap.

:biglaugh:

[alba_tdi]

Hi glynnd,
Thanks again for taking time to reply.
The misfire is only when the engine is hot, i can almost set my watch to the specific time it will happen on my journey from work each day, that's how regular the misfire is. Once the engines up to temperature it starts.
I have tried a diesel conditioner additive in case there was a suspect injector but that did not work either, i have drained the fuel filter to see if there was any water or dirt present but that was clean.
I have found another local garage who can do a diagnostic check using VAG.COM? software, can this check injector pressures i wonder?
The cars booked in for Thusday this week, i will post a reply to let you know how i get on.
What is the problem with No3 injectors and how easy are they to get into for changing?
Presumably you have VW experience of labour costs, something i am trying to avoid.
Cheers.

alba_tdi
:beerchug:

[glynnd]

What is the symptom you are calling a misfire?
Is it a noise or can you feel the engine jerking and losing power?
Not altogetther sure about injector 3 as this was mentioned to me as a possibillity with a fault I had with my car, although I did at the time dismiss this myself.
Have you tried disconnecting the fuel temp sender? as this miss is only there when its warm. When did you last have the cam belt changed as incorrectly fitted can cause the engine to miss. (timing etc)

:biglaugh:

[alba_tdi]

Hi glynnd,
The car is losing power, jerking and generally starts on one cylinder but could go onto two. Accelerating tends to let you rev through the misfire but gives a lot of black smoke out of the exhaust, typical of a lot of unburnt fuel.
If it was a petrol car you would swear the HT lead or plug lead was faulty.
Disconnected the fuel temp sender when the car was stationary and misfire was present and it made no difference.
Timing belt was changed about 2 months ago.
Spoke to someone today who refurbs VW diesels and they confirmed PD engine has problems with injectors. VW price £377 each plus vat.......
Cheers again.
alba_tdi
:beerchug:

[glynnd]

Can the injectors be re conditioned?

:biglaugh:

[alba_tdi]

Injectors can be re-conditioned but i am unsure of the cost. Service exchange injectors are also available, the best price i have found is £400 + VAT per set.
It seems i will need the injector number taken directly off the injector to make sure i get the right ones, of course that means taking off the rocker cover and i presume removing the injector to get the number.
Alternatively i could go to VW and get the correct part number off them and see if i can cross reference the number to get a service exchange set.
I have also been told that there is a procedure to try to reset the injector pressures by means of adjusting a locknut on the top of the injector, i will need to look into this further as it will probably be the first step i would follow.
Whichever way you look at it it's going to be a costly repair that i am not 100% sure is going to work.
I have never had so much trouble with any VW i have owned and it's starting to pee me off!
Thanks again.
alba_tdi
:beerchug:

[alba_tdi]

Just to let you know VAG diagnostic check revealed No 2 injector faulty. When i say faulty i mean an electrical fault. A phone call by the garage to VW confirmed that the fault was in the wiring loom that is connected to a plug on the back of the head and then inside the cambox to the injectors. This part of the wiring which is housed internally has, according to VW, become brittle.
Price for new part of the loom is only £35, plus fitting.
VW seemed very aware of this problem and reported this happening after about 80,000 miles to other vehicles.
Thanks again to glynnd for all help.
Cheers.
alba_tdi