Engine hesitates when cold?

[g10chy]

My car has recently started to hesitate when cold. Its most noticable when leaving my works car park as they have a 20mph limit. Sitting around 20mph the engine starts hesitating, easiest way to describe it is as if im lifting on and off the throttle a little bit.

Once the engine is warm the problem goes away but it can be abit lumpy at idle.

Had a garage run a diagnostics but they did not find any fault codes and said come back in a few weeks when the issues gets worse.

Do any of you guys have any ideas what it could be causing the problem?


Cheers,
Chris

 

[AndyMac]

Dodgy coolant temp sensor can cause those symptoms, telling the ECU the car is warm when it isn't, but it could be any number of things. Is your temp gauge behaving itself?

 

[ikbenben]

I have the same problem. Coolant temp sensor G62 is allready replaced.
Could it be a dodgy secundairy air pump? This will be removed next weekend.

 

[Andy´]

I actually got the same problem too. My temp gauge sits perfectly at 90 since I changed the thermo.

Maybe it would be a good idea to change the sender?

 

[g10chy]

Yeah my temp gauge is behaving its self. How much is a temp sensor?

 

[Welly]

I have the same problem. Coolant temp sensor G62 is allready replaced.
Could it be a dodgy secundairy air pump? This will be removed next weekend.

Won't be the SAI I wouldn't of thought, only fires up on first start, and only pumps air through the head to warm the cats quicker.

Most of these sorts of problems are perished hoses (boost/vac leaks) on the inlet manifold, or around the N75 pipework which allow unmetered air into the engine. Very common for giving lumpy idle especially.

I have never seen an untouched 1.8T engine of any variant without a vac leak somewhere. Bear in mind that most of these engines are over 5 years old, many getting to 10 years these days. Rubber hoses don't last that long in a hostile environment like an engine bay.

Check your hoses, or if you have VAG COM then check engine measuring block 032. First value gives short term fuel adjustment. Any over +/-5% means something isn't quite right, and generally indicates vac leaks (due to the engine taking fuel away to adjust for unmetered air).

Changing the G62 temp sender not a bad shout - BUT one of you said said this has already been done, so can't be this in your case.

 

[g10chy]

Oh and when it was in Audi for service the technician said it took longer than normal to reach temperature.

 

[Andy´]

I have checked block 032 and I was given a value of -0.2% so it might not be vac leak in my case.

 

[Welly]

I have checked block 032 and I was given a value of -0.2% so it might not be vac leak in my case.

Nope, you're spot on! :thumbsup:. In your case, change the CTS (Coolant Temp Sensor).

Go with a genuine part.