Can a Faulty Coolant Temp Sensor Cause Judder/Lumpy engine 1600-2000 rpm???

[graemer147]

I recently wrote a thread on how my car was very lumpy and juddery between 1600rpm and 2200 rpm. Yesterday i had the car on vagcoms live data which told be after 15 mile motorway driving and 15 mins idling the coolant temp was still only 71 degrees. Diagnosing this as a possible faulty coolant temp sensor i was wondering if this could cause the car to run lumpy/judder at the above revs??? The sender is reading but the temp gauge only goes max to 75ish never does it reach 90 degrees which im now told it should. Could anyone help me on this situation please??? I took the connector off the sender and it changed things but still ran quite lumpy Please help!!!

[Peter D]

you need to actually measure the engine coolant temp as it may in fact not be heating up due to a faulty stat. You could put a peice of cardboard over 75% of the rad and see if the temp goes up to 85/90. If it does then I suspect the stat has failed. Report back and tell up your engine code, it is on the ID label in the Spare wheel bay. Regards Peter

[Sam]

Peter's got you on the way to diagnosing the issues.

To answer the question in the thread title, yes a faulty CTS will cause fluctuating/lumpy idle.

[graemer147]

Hi there, Thanks for the fast reply. The engine idles like a dream no erratic reving etc at all the only problems i get at all are the juddering/lumpiness at 1600-2000rpm. I am getting the temp sensor changed today so hopefully this will solve it other than that i shall meanwhile try and do what peter said and put some cardboard in front of the radiator. I just dont understand the juddering as it is so annoying and im only getting 28mpg is this normal???

[Peter D]

Do you have a multi meter that measures resistance and what is the engine code. Regards Peter

[graemer147]

Hi there peter, Im afraid i dont have a multimeter but i know the engine code is AYM!!!

[Christofy]

Hi there,

i know it was a while ago for you but my 2002 A4 is having the same symptoms as yours did. I'm changing coolant temp sensor and stat tomorrow night. Just wondered if it made engine run a bit better as I'm thinking it might be over fuelling because engine is or it thinks it is running cool.

I basically get slight judder when engine is under load between 1600 and 2200rpm like you did. Mpg is down a bit to.

[Christofy]

I recently wrote a thread on how my car was very lumpy and juddery between 1600rpm and 2200 rpm. Yesterday i had the car on vagcoms live data which told be after 15 mile motorway driving and 15 mins idling the coolant temp was still only 71 degrees. Diagnosing this as a possible faulty coolant temp sensor i was wondering if this could cause the car to run lumpy/judder at the above revs??? The sender is reading but the temp gauge only goes max to 75ish never does it reach 90 degrees which im now told it should. Could anyone help me on this situation please??? I took the connector off the sender and it changed things but still ran quite lumpy Please help!!!

Hi there,


i know it was a while ago for you but my 2002 A4 1.9 tdi 130pd is having the same symptoms as yours did. I'm changing coolant temp sensor and stat tomorrow night. Just wondered if it made engine run a bit better as I'm thinking it might be over fuelling because engine is or it thinks it is running cool.


I basically get slight judder when engine is under load (pulling away) between 1600 and 2200rpm like you did. Mpg is down a bit to. Idles fine to!

thanks Chris

[Millerboy79]

Hi, newbie here! I have an issue with my cts too, i hope :-/. My temeprature gauge doesn't read at all and the car can also be awkward to start when warm, plus my mpg after 100 miles of mixed driving is only 26. Is this normal?
Cheers Todd

[pugville]

Just posted up a similar issue this morning on my avf a6. Hope it's not the stat as I just changed timing belt etc yesterday!!!
Coolant temp sender ordered as my temp gauge never goes above 70-80....
love to hear how others have gotten on after changing
Damien