Rough idle on cold start 2003 alh

ghitaboamba · Oct 18, 2017

I have the following symptoms:
* Rough idle on first start in the morning, even in the summer, for about 20 - 30 seconds (it is longer on colder wheather) then the engine smoothes out and all the starts are ok later during the day.
* If I press my accelerator pedal to the floor while I'm cranking, the symptom is almost unnoticeable.
Compression is good in all 4 cylinders
Battery good
Starter good
Fuel filter new
Air filter new
Glow plugs good
I suspect a fueling related issue ...
Please give me your thoughts only if you had the exact same issue and avoid pouring BS about glow plugs, starter, battery or similar.
Thank you in advance!

Nevada_TDI · Oct 18, 2017

Seeing as I just went through a long list of symptoms that included the ones you describe, I will bet if you hooked up VCDS your IQ is jumping all over the place. Jumping all over the place not in the gross sense where it is going to throw a code, but just enough to have the idle hunting. Your mention of throttle on the floor reduces the symptom to unnoticeable, yup, IQ is going to be my guess. If you don't use any kind of a lubricity additive, I suggest you start now, and if you already do maybe try a different brand or more of what you currently have on hand.

UhOh · Oct 18, 2017

Timing

Thermo-T (pay close attention to the connections at your fuel filter)

Nevada_TDI · Oct 19, 2017

Yes, it could also be timing, but you don't mention a recent event where the timing was adjusted or changed. Did you drain the old filter and check to see if there was any water in it, if there was that could explain the symptoms you are having; the Quantity Adjuster hates water and will sometimes stick on the slide it operates on after water has been found. I sincerely hope there is nothing wrong with your pump.

jokila · Oct 19, 2017

ghitaboamba said:
I have the following symptoms:
* Rough idle on first start in the morning, even in the summer, for about 20 - 30 seconds (it is longer on colder wheather) then the engine smoothes out and all the starts are ok later during the day.
* If I press my accelerator pedal to the floor while I'm cranking, the symptom is almost unnoticeable.
Compression is good in all 4 cylinders
Battery good
Starter good
Fuel filter new
Air filter new
Glow plugs good
I suspect a fueling related issue ...
Please give me your thoughts only if you had the exact same issue and avoid pouring BS about glow plugs, starter, battery or similar.
Thank you in advance!

So let's see what i read here....

OP wants you to take time from your day and help him with free suggestions to his problem. Oh yeah, he does not what your opinions and anecdotes because he doesn't have time for that nonsense. However, he did have time to respond to a thread that hasn't had a post in 10 years and criticize those responses as a newbie to this forum.

Nice way to introduce yourself. Don't worry about me offering any opinions or anecdotes to this important thread. Everything I have said above was a fact.

UhOh · Oct 19, 2017

jokila, yes, you are correct, BUT... this isn't only about the OP, it's about information, information that someone else coming along, someone else that's a little more humble and gracious, might find useful.

ghitaboamba · Oct 19, 2017

I would like to thank Nevada_TDI and UhOh, for the constructive comments and suggestions.

I will definitely check the filter again (It contained no water at all when I changed it), I will try to use a different additive (I tried some Lucas diesel treatment additive but it only made my engine noisier and I stopped), and I'll keep you posted as soon as I have any news.

ghitaboamba · Oct 19, 2017

jokila said:
So let's see what i read here....
OP wants you to take time from your day and help him with free suggestions to his problem. Oh yeah, he does not what your opinions and anecdotes because he doesn't have time for that nonsense. However, he did have time to respond to a thread that hasn't had a post in 10 years and criticize those responses as a newbie to this forum.
Nice way to introduce yourself. Don't worry about me offering any opinions or anecdotes to this important thread. Everything I have said above was a fact.

Jokila, it's not about my time its about this forum. I would rather leave space for really knowledgeable people whom are actually able to repair stuff, who have positive results and can indeed help others and we'll all benefit from it.
But you have the right to disagree with me ...

Cheers

ghitaboamba · Oct 19, 2017

Nevada_TDI said:
Seeing as I just went through a long list of symptoms that included the ones you describe, I will bet if you hooked up VCDS your IQ is jumping all over the place. Jumping all over the place not in the gross sense where it is going to throw a code, but just enough to have the idle hunting. Your mention of throttle on the floor reduces the symptom to unnoticeable, yup, IQ is going to be my guess. If you don't use any kind of a lubricity additive, I suggest you start now, and if you already do maybe try a different brand or more of what you currently have on hand.

Nevada_TDI,

Is there a place in VCDS where one can change the cold start IQ or something related to that?

UhOh · Oct 19, 2017

There's no "cold start adjustment." IQ is a base reference point on the Quantity Adjuster. IQ "can" affect things, both starting and running

You're a resourceful person, lots out there on checking IQ and changing it (either via VCDS, though this is only really good for fine-tuning; "hammer mod" is the better way for more substantial changes).

Nevada was talking about a problem with the IP, the IQ bouncing around. A good IP won't do that: of course, one can still set the IQ wrong on a good IP.

I'd think that checking IQ and telling folks here what you find might be the best thing: do data gathering first; problem-solving second.

ghitaboamba · Oct 19, 2017

UhOh said:
Timing

Thermo-T (pay close attention to the connections at your fuel filter)

UhOh,

It is very possible because I experienced the same symptoms when I first started the engine after changing the fuel filter. It was on a warm engine.
Can you explain how the Thermo-T works? How can it cause a rough idle? Is it possible to bypass it for a test?

ghitaboamba · Oct 19, 2017

UhOh said:
There's no "cold start adjustment." IQ is a base reference point on the Quantity Adjuster. IQ "can" affect things, both starting and running

You're a resourceful person, lots out there on checking IQ and changing it (either via VCDS, though this is only really good for fine-tuning; "hammer mod" is the better way for more substantial changes).

Nevada was talking about a problem with the IP, the IQ bouncing around. A good IP won't do that: of course, one can still set the IQ wrong on a good IP.

I'd think that checking IQ and telling folks here what you find might be the best thing: do data gathering first; problem-solving second.

From what I remember since I connected my laptop to my car the IQ was at 23 and it would not go below that (I guess I have to try hammer mode) but if I am not mistaken it was within specs.

The fact is when you want to adjust the IQ the engine should be at working temperature but the problem manifests when first starting the engine in the morning (even in the summer) ...

UhOh · Oct 19, 2017

I'd take another look with VCDS. I don't think that IQ can register 23.

Thermo-T can crack and you won't know it. ANY crack/hole in the fuel lines will result in air incursion. Air in the fuel system will cause hard starts (especially when cold).

Data gather first!

Genesis · Oct 19, 2017

What UhOh said.

I had a damnable problem for a while several years back with my '03. Warm, never a problem. Cold, never a problem except if you started the car, backed it out of the garage (or otherwise ran it for a very short period of time) and then shut it off.

IF you did that it would take a VERY long crank to restart. I chased that for a good long time as there was nothing obvious wrong (e.g. no air bubble in the clear line, etc), and finally found a tiny air leak - no fuel was leaking out, but that little bit of air, under the "wrong" circumstances, was just enough to cause trouble.

Since fixing that it starts first crank, every time, no matter the circumstance.

jokila · Oct 19, 2017

ghitaboamba said:
Jokila, it's not about my time its about this forum. I would rather leave space for really knowledgeable people whom are actually able to repair stuff, who have positive results and can indeed help others and we'll all benefit from it.
But you have the right to disagree with me ...
Cheers

Thank you for posting what obviously has been going on here, for YEARS. I think the forum was doing fine about that and doesn't need you deciding what is worth posting, especially if it wasn't your post (your other rant) to begin with. You came across as arrogant and a tad foolish.

Here's my final point. Some people contribute indirectly even if they aren't exactly focused on the answer. It sometimes helps the conversation many times bringing out thoughts from other contributors. We have our own watered down Socratic method where people can contribute freely. Don't be that guy who is short on patience about getting what is basically free help.

ghitaboamba · Oct 20, 2017

Genesis said:
What UhOh said.

I had a damnable problem for a while several years back with my '03. Warm, never a problem. Cold, never a problem except if you started the car, backed it out of the garage (or otherwise ran it for a very short period of time) and then shut it off.

IF you did that it would take a VERY long crank to restart. I chased that for a good long time as there was nothing obvious wrong (e.g. no air bubble in the clear line, etc), and finally found a tiny air leak - no fuel was leaking out, but that little bit of air, under the "wrong" circumstances, was just enough to cause trouble.

Since fixing that it starts first crank, every time, no matter the circumstance.

Thank you Genesis and everybody else! I'll order a brand new Thermo-T as soon as I can, also the o-rings, to see if it will make a difference.

Cheers ...

UhOh · Oct 20, 2017

You can just directly connect the return line from the injectors to the tank return line to eliminate/test for any Thermo-T issues (though you'd need to, in-place, plug the ends of the Thermo-T).

rrgrassi · Oct 21, 2017

Also check the braided return lines for seeping. That can allow air in, and cause a stumble or misfire when doing a cold start. That is what caused my issue.

ghitaboamba · Oct 21, 2017

UhOh said:
I'd take another look with VCDS. I don't think that IQ can register 23.

Thermo-T can crack and you won't know it. ANY crack/hole in the fuel lines will result in air incursion. Air in the fuel system will cause hard starts (especially when cold).

Data gather first!

I meant 2.3.

Here are some VCDS screenshots:

Also a video of the clear hose while running ...

http://pics.tdiclub.com/data/533/AirInClearHose1.wmv

I had bubbles in the hose since I bought the car in 2013 but lately they seem more ...

Is this normal or there should be no bubbles at all?

UhOh · Oct 21, 2017

OK, yeah, a decimal point makes ALL the difference!

You're within spec, IQ will vary a bit. What you're showing doesn't seem at all like a problem. Might look to bump this up a bit, though I don't believe that this is necessarily the source of your starting troubles. BUT...

What's up with that low idle speed? You should be seeing 903 rpm. What is your timing set at? Did someone change the adaptation for idle speed?

Group 013 looks great! I'm a HUGE fan of this data being able to provide an overall assessment of an engine.

I am currently bandwidth challenged, in which case I cannot view the video, sorry.

On the bubble front... I'd double-check your fuel return lines (fuel filter bits- o-rings, hoses, Thermo-T etc.) Air incursion makes for problematic starts (and early running issues until the engine can compensate and purge the air). Bubbles are, up to a point, OK.

ghitaboamba · Oct 22, 2017

I was the one who changed the idle speed for fuel economy purposes (don't know whether that helps).
Today I have replaced the fuel preheat valve (Thermo-T) and there are no bubbles in the clear hose anymore. I will keep looking but today I took the car for a spin after changing the Thermo-T and when I came back checked again and no bubbles still.
Tomorrow when I start the car in the morning I will check to see if this changed something relative to my starting problem.
For now I thank you all for all this help!!!

UhOh · Oct 22, 2017

The amount of fuel savings from changing the idle speed is so insignificant to not even register. Try to keep your adaptations stock such that your ECU has better full range to work with.

BTW - My tunes set idle high (1150?) until warmed up. All my cars (Golfs) average over 50mpg (highway driven): I'm pushing around 52 mpg of late.

ghitaboamba · Oct 23, 2017

UhOh said:
BTW - My tunes set idle high (1150?) until warmed up. All my cars (Golfs) average over 50mpg (highway driven): I'm pushing around 52 mpg of late.

I would like to have the same thing. Is it possible to set it up this way? On mine is always the same (except when very cold -20 celsius or lower).

This morning I did not have the rough idle issue. I am pleased with the change. I have to check when it becomes colder outside but so far the results are encouraging.

UhOh · Oct 23, 2017

You'd have to get a tune in order to have that function. It is offered free for some/many tunes, so I decide I'd do it. I supposed one could get a tune for just this, but it would tend to be a bit costly since all the same hoops need to be jumped (need to flash the ECU). For me, however, it's not of a lot of use, as we're just a short stretch and then it's highway for many miles: the daughter, who lives elsewhere, does mostly city driving, so this mod in her car it is more useful.

Genesis · Oct 24, 2017

It is of almost-zero value, however, to do so even in cold weather.

These engines simply don't develop enough waste heat unless they're under load.

BobnOH · Oct 24, 2017

ghitaboamba said:
I was the one who changed the idle speed for fuel economy purposes (don't know whether that helps)............................!!!

Put it back. With the coolant at least 80c you want to see 903. When it's cold it should bump a little.

Technician! · Nov 10, 2017

Genesis said:
What UhOh said.

I had a damnable problem for a while several years back with my '03. Warm, never a problem. Cold, never a problem except if you started the car, backed it out of the garage (or otherwise ran it for a very short period of time) and then shut it off.

IF you did that it would take a VERY long crank to restart. I chased that for a good long time as there was nothing obvious wrong (e.g. no air bubble in the clear line, etc), and finally found a tiny air leak - no fuel was leaking out, but that little bit of air, under the "wrong" circumstances, was just enough to cause trouble.

Since fixing that it starts first crank, every time, no matter the circumstance.

Where was your air leak into the fuel line coming from? Is there a "common" source for this problem? I too, have VERY long crank times when it is colder than 30 degrees F outside, and vehicle has sat for more than 6 hours.

Genesis · Nov 10, 2017

Mine turned out to be in the Thermal-T -- it had a very tiny crack in the body, so despite looking just fine, the O-rings being just fine, and not leaking any visible amount of fuel it was leaking a bit of air into the filter, which then got drawn into the pump.

BobnOH · Nov 10, 2017

Gotta keep an eye out for that!
OP- Never heard of rough cold idle from a thermostat.
Since you got the VCDS device go ahead and check all the temperature sensors when cold (ambient) and hot. Look for anomalous readings.
Here's a reference
If you have high mileage on the injectors, maybe run a can of Diesel Purge straight.
Also verify the glow plugs are working, they are used, even in relatively warm temps./

NaTaS02 · Sep 25, 2019

I had a Beetle with same problem. It was sucking oil from the turbo and it settle in the intake and burn off during a cold start. It needed an EGR gasket, round O ring

Rough idle on cold start 2003 alh

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