SDI Idle jumps occasionally

[poiuytre111]

My 2001 SDI (97k)  is running very well generally - my usage pattern tends to be whole days starting with a longish run then gaps of an hour or two so parked up -  the car is more or less running warm all day.

 

I have noticed lately that (when warm) it sometimes returns to a higher idle speed of about 1100 rpm c.f. the normal 900 rpm. Also when warm starting, I occasionally find it starts with a succession of short bursts of higher revs - as If I was trying to wind someone up at the traffic lights by blipping the accelerator. Again this will continue for a few mins if I re-start but then go away.

 

Car is due for a new cambelt next week so if there anything I should ask the specialist to look at - egr or crank breather perhaps ? Otherwise I am tempted to put some injector cleaner in the next tank to run through the injection pump.

[sepulchrave]

Just get the car checked for fault codes while it's in for the cam belt and take it from there.

[AdamOP94]

Mine has a high idle sometimes and if I flick the accelerator up with my food (like a motorbike gear) it drops back down.

Based on that, I assume my pedal just sticks being as it's electrical.

[trundlenut]

My old octavia did this (same type of injection pump diesel) and a faulty coolant temperature sensor gave very similar symptoms. A fault scan is a good idea to confirm though.

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[poiuytre111]

My old octavia did this (same type of injection pump diesel) and a faulty coolant temperature sensor gave very similar symptoms. A fault scan is a good idea to confirm though.

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Thanks for that - temp guage is a bit iffy so I will take a new sender with me when I get the belt done - excellent !

[trundlenut]

Thanks for that - temp guage is a bit iffy so I will take a new sender with me when I get the belt done - excellent !

If it is the CTS, then it should give an implausible signal fault. The octavia has a dual sensor CTS, with one feeding the instrument cluster and the other the engine ecu. I thought the Fabia uses a single sensor, so a problem would show up as a wobbly temperature gauge. I don't know if the Fabia ones are as prone to failing as the early octavia ones.

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[felicia16v]

Yeh sounds like a faulty cts to me

May not have a fault logged sometimes it's easier to log the reading on vcds to spot fluctuations in its reading as the gauge is pretty slow to react and is heavily ballasted towards staying in normal range.