1.4 Tdi slightly rough sounding start up from cold

E

Evoman

Member
I've recently changed the thermostat on my A2 and she gets up to temp 90 degrees now and stays there.

Recent cold mornings the start up is a little rough almost like the car is running on two momentarily.

From what I've read on here it sounds like perhaps temperature sender or glow plugs?

I've had my local friendly garage plug in a diagnostic to see if any fault codes are registering but none are showing. I was hoping that would point me in the right direction.

The glow plug light is notably staying on a little longer once the ignition is on turned on during these cold mornings but I guess that is normal.

Car runs and starts great when warm and seems to run fine after this slightly rough cold starting.

Any tips? Go for the temperature sender? Should it be showing a code fault?

Cheers
 
Evoman said:
I've recently changed the thermostat on my A2 and she gets up to temp 90 degrees now and stays there.

Recent cold mornings the start up is a little rough almost like the car is running on two momentarily.

From what I've read on here it sounds like perhaps temperature sender or glow plugs?

I've had my local friendly garage plug in a diagnostic to see if any fault codes are registering but none are showing. I was hoping that would point me in the right direction.

The glow plug light is notably staying on a little longer once the ignition is on turned on during these cold mornings but I guess that is normal.

Car runs and starts great when warm and seems to run fine after this slightly rough cold starting.

Any tips? Go for the temperature sender? Should it be showing a code fault?

Cheers
Click to expand...

The temperature sender failing will not throw a fault, the system just thinks it is cold (or warm depending on which way it has broken)

Similarly if the glow plugs are not in top condition there would be no fault, only when they have failed.

So do the easy one first and change the temperature sender (even though the dash temp is showing correctly the other circuit in the sender MIGHT be sending the ECU the wrong temperature).

Then if that makes little or not difference get the glow plugs out and check / replace them.

The glow plug light stays on longer when the engine is cold, but it does vary.

Steve B
 
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Fiddly job this one. I reckon once you've done it once it would be pretty straight forward with the 'know-how' a second time.

Replacement sensor, o-ring and clip from Audi, fitted along with coolant top up. That clip is awkward until you get it.

Started her up once fitted and smooth running straight away.

I had thought performance had tailed off slightly. Now the little thing is genuinely quick, really impressed with the wee A2.

Spot on advice and guidance on here yet again :D

Whilst in the Audi dealership I picked up a copy of the Audi magazine, flicked to the last page where was an A2 and discussion on upgrades with input from Steve I believe from on here. Great little article :)
 
Hmm.. have an ATL engine, and always found the glow circuit strange as glow is on just for 2 sec regardless outside temperature. Can start slightly rough.

Is this temp sensor something applicable for ATL engine as well? Where can I find more info about the temp sensor; part number?
 
Could you inadvertently have bumped the earth connection to the starter motor? Is it not in that general area? Maybe not getting full juice. Mine is the same after my stat change and I'm planning on having a look tomorrow?


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Olerype said:
Hmm.. have an ATL engine, and always found the glow circuit strange as glow is on just for 2 sec regardless outside temperature. Can start slightly rough.

Is this temp sensor something applicable for ATL engine as well? Where can I find more info about the temp sensor; part number?
Click to expand...

Yup I had mine replaced a few months back ... Also known as the "green" sensor at the base of the engine.

When that didn't work in relation to my cool running issue I then replaced the thermostat.

Pinky can tell you how that works :)

Oh and if it's any consolation my ATL is starting rough just now also!
 
Pinky can tell you how that works :)

Oh and if it's any consolation my ATL is starting rough just now also![/QUOTE]

I don’t think Evoman is quite as technically limited as me. I’m special.

I’m not sure if mine is quite rough - feels like it isn’t going to start... lights really begin to dim (more than normal)... a couple of times it’s thrown up an error code (steering wheel and exclamation mark?)... then caught... then runs absolutely fine. The whole thing takes maybe three seconds - it’s more that it makes me nervous that it won’t start.

It only hasn’t started first time twice and it caught the second each time. Doesn’t seem to matter if I’ve just done a long run. If it’s hot or cold. I’m going to check the starter Earth.


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Starter earth will be your culprit - you need to wire brush all the crap off it, probably install a new bolt (use a stainless one) and then smother the area in battery terminal grease - it'll protect from future corrosion but still allow good electrical contact.
 
Starter is brand new Bosch, so this is not the issue. Car starts every time, just more rough than my other Touran TDI. There is no difference in time for glow circuit with respect to outside temp, so that why I suspect something wrong with glow circuit.
 
Assuming battery checks out in relation to voltage output?

Indeed what level is expected or at what point cold you point a finger at the battery? Above or below 11.5ish v or thereabouts?
 
likely to be one of the Glow plugs as failed, that cylinder will not fire until the engine as done a few revolutions and will then come on song. Not a real problem until a 2nd glow plug goes faulty then with only 1 left you will have real starting problems in the cold weather
Cheers,
 
Pinkythelabrat said:
Ooh, dear! Would that throw an error message? ☹️

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Click to expand...

Hey Pinky, I've read on here the glow plugs are really quite accessible on the little A2 compared to some cars so not necessarily a big deal to replace.
Look up the threads on here, tips include ensuring the engine is hot before attempting to remove and perhaps prior to that get some ant-seize penetrant sprayed onto them and let it soak in over a few applications over a few days.

A previous car I had did show glow plug error codes but they were potentially very difficult to remove and I would never have attempted that before but on the A2 it's a great little car to learn diy skills or just get very cold and test your patience in this weather :p

Good luck!
 
Indeed, glow plugs on the 1.4 TDi are a doddle to change. You just need a deep-reach 10mm socket and a bit of mechanical sympathy.

Start off by removing the engine cover (yes, that's the black piece of fibreboard) and then you'll see the 3 glow plugs hiding behind the fuel rails, with their electrical feed conduit going to them

If they won't undo easily, then soak a bit of anti-seize into the threads and leave overnight. The, when they're out, simply screw back in hand tight, plus a 1/3 turn and re-attach the leads to them.

Photo showing the AMF engine below - you can't fail to spot the plugs:

s-l1000.jpg
 
Yup kinda obvious even for me.

When I bought the car back in June I did have errors logged for glow plugs and asked for them to be replaced. Errors now gone on this but I've since discoverd the guys I used to do this work are charlatans... Stuff I asked them to do was not done but I won't bother with the detail here.

Question is if I have no diags for glow plugs coming up do I still have an issue? If so anyway to tell how new the plugs are?
 
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Be warned. Glow plugs also snap quite easily without you needing to do anything.

I had a glow plug code so decided to replace them at a service a couple of years ago. The tops just spin because they shear off the body and you end up with plugs you can't get out. I still have 2 broken plugs in there. No lights, still starts ok. Maybe a bit rough when really cold... But starts fine every time.
 
KekseKaempfer said:
Be warned. Glow plugs also snap quite easily without you needing to do anything.

I had a glow plug code so decided to replace them at a service a couple of years ago. The tops just spin because they shear off the body and you end up with plugs you can't get out. I still have 2 broken plugs in there. No lights, still starts ok. Maybe a bit rough when really cold... But starts fine every time.
Click to expand...

You can test for a plug failure easily by removing the wire and applying a voltage to the plug end and measuring the current drawn. From memory the early A2 used a 12volt plug, so applying 12volts to the plug is same, should draw about 10 amps maybe a little more (the end of the plug glows red when its working, so a lot of amps used to produce the heat) I think the later A2's used a lower voltage glow plug, therefor applying 12 volts to these glows would likely damage them, I think from memory the later plus are 5 volt plugs

cheers
 
My ATL has brand new overdimensioned battery, starter and glowplugs.

And agree with warning for glowplugs. I got the old broken ones removed easily, but the new ones would not fit, and bolt treads in aluminiumtop had to be redone. Glow plugs were from dealership.
 
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