Hi All

 

I hope someone may shed some light into what is going on with my 2014  1.2tsi 16v  CJZC  Polo.   41k miles.

 

1)  When I start the engine from cold - it behaves fine,.... i.e.  slightly higher idle for a brief moment, then quickly settles perfectly on +/- 650rpm

2)  When I start the engine warm-hot, ....after some journey, ...it also behaves absolutely fine. (same as above)

 

3)  BUT when I start the engine +/- 4hrs after stopping, ...it will start with a higher rpm (approx. 1200) then within the next minute or so, will slowly go down and eventually settle on 650rpm.  During this settle-down time the car tends to shake ... and IF I drive it during this time, it sounds throaty.

 

I believe it must be temp related, because on a hot sunny day, this "goldilocks" hesitation zone is longer,  i.e.  around 6hrs after stopping,.... and on a very cold day it is shorter, i.e. around 2.5hrs.
Any other time,... earlier or later than this "goldilock" zone causes NO probs.  and the car idles perfectly immediately.

 

Recently my O2 sensor2 died (after cat) so I replaced with the approved Bosch (long cable) and reset the fault codes via (limited) diagnostics - and for some time this hesitation problem seemed to be slightly less, .....but now it's the same as before.       I fitted the new after-cat O2 sensor around 2 months ago.

 

I would like to ask what might be causing this limited starting hesitation... anyone else have or know about this prob ... and what to do ?

 

Maybe?   pre-cat O2 sensor,  coolant temp sensor,  temp sensor for fuel pressure,.. or something else  be the root cause ?

 

I bought the car new ( in 2014 ) and this issue has only shown itself since needing to start/stop after around 4hrs !!  (on a normal day)

 

Thx in advance for any tips.

 

 

That's a weird one for sure. 

 

You can check the temp sensors, by buying a dirt cheap elm bluetooth obd adapter and monitor the temps on your phone in real time.

 

Does your car need oil top up's regularly? Maybe a bad seal on the turbo is filling your intake with oil causing it to run rough when you start it. Maybe a bad coil is the issue. Try running a diagnostics test and see if anything comes up.

 

I would also check the spark plugs as they can indicate if a cylinder is running lean/rich or misfiring.

Hi.  Thx for your reply.

 

I changed the spark plugs 2 yrs ago and my   Autophix VAG diags  shows no engine fault codes at all.

The oil never needs topping up, and I change oil/filters every year.

 

Anytime I start the car outside of this "goldilocks" zone (before or after) , the car behaves perfectly.

 

My autophix doesn't show realtime.  I have no probs to buy a new coolant sensor and change (preventitvely).   Just wanted to ask around if anyone has seen this issue.

 

Thx again.

P

If the coolant temp gauge is reading OK then it won't be any point in replacing the sensor as on your car the sensor feeds the ECU and it sends the information to the gauge via the CANbus system 

 

You need to get it on a diagnostic reader that will read "Live data"  then you could look at the air inlet temperature readings 

Hi.  OK

 

I will definitely look online for a cheap elm bluetooth obd adapter and connect it up.

I am not exactly sure what I will be looking for, concerning the right/wrong readings, and also as this hesitation/shaking goes away within 1 minute of starting (during this specific time zone)

 

Someone also noted that usually the O2 sensors go/play up around the same time, so .. also thinking if the pre-cat O2 sensor should be replaced now as a good idea anyway, if its end-of-life is coming anyway too.  It's about 50notes for the Bosch short cable version.

 

Engine temp dashboard display seems to be all ok.  No strange readings at all.  When warm it's bang-on 90C and slowly gets there during driving from cold.

 

Thx again and I'll post readings from the elm

 

P

 

 

If you can find someone local who has VCDS with that you just need to hover the mouse pointer over the measurement reading and it gives the upper & lower limits 

Hi.   Unfortunately not.  The only ones with that would be service centres here and would charge an arm/leg and book it in sometime in August - as they're all too busy !!  (sigh)