Very rough starts on my ALH

[Smokey Eddy]

Yeah well thanks buds perhaps I don't have one. It's not MY car. Just asking some questions my grumpy pants.


Jer, its about ...-1 at night.

[Vincent Waldon]

When its cold, the glow plug light doesn't stay on for very long at all

IMHO this ^^^^^^^^^ needs to be looked into long before timing or IQ.  

Regardless of temperature you should always get a brief flicker of the glow plug light when starting... as a bulb test.  If you don't get this flicker you suspect relay 109... if you are getting this flicker 109 is probably fine, at least for the purposes of starting.

The glow plugs come into play below about 45F/ 7C... at -1C I'd expect about 5 seconds of glow plug time.

BTW, just like the IDIs the TDIs have a glow plug strip fuse...it's in the fuse box on the top of the battery box.  And just like the IDIs the glow plug light has nothing to do with whether the glow plugs are actually getting power. 

[8v-of-fury]

Ahh see what posting from your phone does! You miss stuff!

Vince, if a gp has died what does the ECU do to notify the driver. So the light not staying on means the plugs are not seeing power.. EDMUND try jumping the plugs! I am confident this will solve your rough start problem

[Vincent Waldon]

Vince, if a gp has died what does the ECU do to notify the driver

It throws a code (P0380 most often on the pre-2002 cars) and triggers the CEL.  It should do this if the fuse goes as well.

So the light not staying on means the plugs are not seeing power.

Unfortunately no... just like our IDI engines the light is a "wait until I go off before you start" light rather than a "the glow plugs have power" light.

[8v-of-fury]

Right, so then being like the idi engines.. the light will go off when the relay has kicked out. The light stays on for a second and goes out meaning even if the plugs were getting power it was only for a secondÉ (that means a question mark my browser is being funky)

[Vincent Waldon]

Right, so then being like the idi engines.. the light will go off when the relay has kicked out.

Nope... 'cause now the system is different.  

Assuming the engine starts the TDI glow plugs stay on for 3-4 minutes even if they didn't come on to start it in the first place.  Spring/summer/fall/winter... the glow plugs always come on *after* the engine starts, even if they weren't used to help start the engine.

The light says "ok to start me" and that's all... the glow plugs themselves has a completely different mind of their own.   

[8v-of-fury]

Well shyyyoot I thought I had it conquered. Ok well here is another point, if the car eventually starts after cranking indicating lack of gp usage.. and then continues to run rough when the afterglow ¨Should¨ be working.. yet doesn't seem like it is.

Either way, what i am trying to say.. is that the gps dont seem to be working at all.

[nathan_b]

Pull the temp sensor and see what happens (tricks the ecm into thinking temp is max cold)

Then test the resistance from the terminal of the gp to the head. if it is excessive (more than .8 ohm) then replace them. Failed gps have infinite resistance 90% of the time.

[Smokey Eddy]

I already pulled them out and tested them.

[Powered by Spearco]

Does the coolant temp take for ever to warm up?

If its a manual trans TDI, take out three GPs in the coolant flange and swap them with the engine GPs. See if it starts any better. 

Or perform the tests outlined before to verify them being bad.

[Vincent Waldon]

You can confirm by pulling the connector off the sensor on a cold morning... if you get a longer glow plug light diagnosis confirmed.

There's a connector plugged into #6... pull it already and see if the glow plugs come on long time and engine start properly:

[Smokey Eddy]

I will I will!

[coke]

Not sure if this applies to your car or not but I had to modify the glow cycle with Vag-Com on my father's 98 because the glow plugs would come on for pitifully short cycles and it would run rough and start hard.

Replacing the temperature sensor is a great place to start. I know they had some wiring harness defects but not sure they apply to the A4/MK4.  My dad replaced his, I modified the glow time with vag-com and it starts great in all temperatures. Doesn't stumble hardly any and smooths out immediately.  If you have to, after you've exhausted the other possibilities, extend the glow time, I can get you the instructions on how to do it. Just send me a PM.

[blackdogvan]

Does anyone know the part number or year/model/engine code for the GR relay that doesn't use a input from the ECU but stays on for a short time after start & also has the temp input for no GP warm starts? I had one, it died & I forgot the part number.

[Smokey Eddy]

that's what i mean by short. That was one of the warmest days too... i think it was +4 or +6 ... (that is a video by the way. click on the image)
when its cold in the morning like -6 it barely feels like it's going to start...
the sound sucks because its from my phone but maybe someone can say its the starter? (turning slowly)

i should have done the "pull the sensor" trick but im so unorganized all the time im almost always late... i will try tomorrow.