1.4 TDI Cold Start: Troubleshooting & Tips

Hello! I'm new here and I already have a question:
As the owner of a Polo 9N with the 1.4 TDI engine, I'm always surprised by how unevenly the engine runs during cold starts in winter, for about 5 to a maximum of 10 seconds. It also emits a bit of blue smoke. I can also feel some knocking from the engine, as if the cylinders aren't firing properly. My workshop says this is normal. I suspect that the preheating time might be too short, or at least insufficient.
Does anyone perhaps have any advice, or should I just not worry about it?
Thank you very much for your answers.

I wish you a good start to the new year and a happy new year!

Hello,

Perhaps a spark plug isn't receiving power or is defective?
Then it takes a few engine revolutions after a cold start for the affected cylinder to run properly.

Best regards, Rainer.

Just tell him to let it glow for five times during the next cold start in the morning!

If it then starts running smoothly immediately, it indicates that one or more glow plugs are faulty!

That is initially easier than measuring the candles!

'Definitely, it's not normal for him not to start running around immediately in the morning!'

Regards,

Manuel.

Hello,

but if, for example, a glow plug is defective and doesn't glow at all, then pre-heating it 5 times won't make it glow, right?
They're quick to figure out... mass, engine block, glow plug, wire, 55W light bulb, wire, +12V battery. If nothing lights up, the glow plug is dead.

Best regards, Rainer.

Hello,

but if, for example, a glow plug is defective and doesn't glow at all, then pre-heating it 5 times won't make it glow, right?

Greetings, Rainer

Yes.

Regards,

Manuel.

OK, thank you very much, I will follow your advice and pre-heat it 5 times and see what happens!

I've already put a few kilometers on the engine, and my thoughts are:
If you've filled up with diesel (not petrol or biodiesel), blue smoke is absolutely abnormal and indicates a problem with the glow plugs. Many people find that the 3-cylinder engine always runs unevenly when cold, but that's more a matter of opinion.

Regards,

Olaf.

Yesterday, I took the car back to the workshop, and they checked everything! And everything was supposedly fine! But this morning, at -7 degrees Celsius: It cranks..., ..., starts, and it fires up like the engine has already done 400,000 kilometers! There's a little blue smoke, but you can practically feel how poorly the individual cylinders are firing. Also, the engine speed fluctuates about twice between 1200 RPM and 1000 RPM, and then it stabilizes. Honestly, I'm fed up! This is already my second Polo 9N 1.4 TDI that starts so poorly, and I'm just disappointed with this 'fragility'! My neighbor's Clio 1.5 dCi doesn't care about the cold; it starts perfectly and 'humms' contentedly. I think it's time to switch back to Renault.

Hi!
I also have the engine you mentioned. Well, almost. I have the "older" AMF engine, just like Olaf. It's mostly original, with 40,000 km on it. And I certainly can't complain about poor starting characteristics. At the moment of starting, the RPMs only briefly rise to just above 1000 at -10 degrees Celsius, and then immediately drop back to its normal idle speed. I've never noticed any fluctuations, nor have I experienced any dragging cylinders.
Do you always fill up at the same gas station? Otherwise, it might be worth trying a different one for a couple of fill-ups. Apparently, this seems to be affecting the second 1.4 engine as well... that's strange!

Good luck, and let me know how it goes...
Dirk.

I always fill up with either Aral, Esso, or occasionally Shell.
What kind of fuel do you usually use?
I've already tried everything; it runs the worst with Shell.
It's possible that I'm wrong, but I have a feeling that it works better if I wait about 5 seconds after the indicator light goes out before I start. I know that the operating manual says the exact opposite!
Well, what can you do? I guess it just vibrates a bit! But does that actually damage the engine? Mechanically speaking?

Hi,

You are certainly not mistaken in your observation. After the preheating indicator disappears, the device will continue to glow for at least 5 more seconds (this is called "standby glow"), before it actually stops glowing.

I actually monitor this with an LED at my place... If I start the process only when the LED turns off, it runs much smoother than if I start it after the actual display has disappeared.

You can easily observe this:

Turn on the interior lights, turn on the ignition, and then wait. Eventually, after the regular preheating phase is complete, you'll hear a "click" (this is the preheating relay, located on the lower left side of the relay panel in the Ibiza, and it's easy to hear), and the light will become noticeably brighter.

Regarding the uneven engine running... I think the number of cylinders also plays a role. The 1.4 TDI is a 3-cylinder engine, while the 1.5 dCI you mentioned is a 4-cylinder engine.

Best regards,

Jan.

Hi,
The question is, what exactly was understood by "everything" in the workshop, especially how the glow plugs were checked.
The method described in the article, which uses a light bulb, is simple to perform and would provide certainty.
Perhaps that's just normal for a three-cylinder engine. I doubt it can continue to function well if one or even two of the cylinders refuse to fire.

Joohn wrote:

I think the time is slowly coming for a return to Renault.

Before you decide to take that step, I would first recommend going to a more competent workshop. What you are describing is certainly not normal, not even for a three-cylinder engine.

I would like to properly check the preheating system.

1. There may be transition resistances present, which can cause the spark plugs to heat up, but not properly.

2. Glow plugs can also be defective without immediately burning out. In such cases, the glow plug still draws current and can be identified through simple tests using a lamp.

Okay, so check all the cables, fuses, and relays. Also, remove the spark plugs one by one and test them directly by connecting them to the battery.
etc. pp. etc.

Let's test the compression at the same time.

CU Gremlin.

I was at the workshop again today, and the result was:
This is more or less the case with all Pump Duse TDI engines! They have had these issues repeatedly, and the problem has never been resolved. After consulting with the factory, it was determined that all PD TDIs have cold start problems, and there's nothing that can be done about it!
They from the workshop even wanted to give it to me in writing!
Well, I guess I'll just start it up with a rough idle, some misfires, and blue smoke!

Okay, here's the translation:

'Hmm... there are a few cars in the yard, but they all seem to be starting without any problems despite the current temperature of -6°.'

CU Gremlin.