2.0 FSI Poor idle when cold

[MEL744]

Just had something incredibly strange happen. Got in the car, started it up and it idled at 1200 as normal but it was smooth! My brother even noticed it. Seemed to run for a bit longer than usual (at a guess 60 seconds). This seems like how the car should be operating. The only parameters that I can think of as being slightly different are that the car has sat for 48 hours and the fuel level is very low (in the red dashes). Also its very cold in Melbourne at the moment but the car gets garaged so thats probably not related. Was going to make some logs but was in a rush so decided not to.

[MEL744]

About the PCV diaphragm, thanks for the heads up on that one, will be careful not to tear it. The struggle with angled needle nose pliers sounds very familiar... When you say 510 ohms on the heaters, is that constant and for all heaters? Also, tonight on the way home from uni I started it (with low fuel still) and sure enough it idled smooth and for longer at 1200rpm. Only put a bit of petrol in tonight so by the end of the week it will be low again and I can make some logs. Any suggestions for what might be useful to check?

[saabman]

ECU files good luck making any sense of it its for a TFSI but still a 9.5.1 so "should" be relevant" Dropbox - Bosch MED9.5 - Simplify your life
I think I found it on ecuedit.com ?

Im at a bit of a loss as to where to go as well - I had a similar experience - the day I took the car back to my daughter - it started and idled fine interestingly it was low on fuel as well I didnt have the laptop with me and was running late so couldnt check anything - but the android head unit she put in can display some very basic data and the only thing I noticed was the voltage was almost exactly 12V after the car had started normaly it is around 14V. I was wanting to investigate the battery/charging voltage a bit more but that was my last day with the car. Maybe have a look at battery voltage.

I had read about about possible issues with a full tank of fuel and issues with the purge valve - I had discounted that as I had removed the purge valve and blocked the port in the manifold, Ive since replaced the purge valve and no noticable differnce.

[saabman]

As for the Resistance thats for B1S1 and B2S1. The field for B1S2 and B2S2 is blank (MB41 and 42)
510 is out of range acording to the label file Ill need to look into this further
Data:
41 510 ohms Resistance Htg. S1 OFF .......... Htg. S2 OFF
42 510 ohms Resistance Htg. S1 OFF .......... Htg. S2 OFF

Description:

41 0 Lambda Control (Lambda Sensor Heating Bank 1)
41 1 Resistance Bank 1 Sensor 1 Range: 0.0...500.0 Ohms
41 2 Heater Condition Bank 1 Sensor 1 Range: Htg. S1 OFF/Htg. S1 ON
41 3 Resistance Bank 1 Sensor 2 Range: 0.0...0.5 kOhms
41 4 Heater Condition Bank 1 Sensor 2 Range: Htg. S2 OFF/Htg. S2 ON

42 0 Lambda Control (Lambda Sensor Heating Bank 2)
42 1 Resistance Bank 2 Sensor 1 Range: 0.0...500.0 Ohms
42 2 Heater Condition Bank 1 Sensor 1 Range: Htg. S1 OFF/Htg. S1 ON
42 3 Resistance Bank 2 Sensor 2 Range: 0.0...0.5 kOhms
42 4 Heater Condition Bank 1 Sensor 2 Range: Htg. S2 OFF/Htg. S2 ON

[MEL744]

Interesting, so your two sensor 1s are behaving the same as my single sensor 1... Will give the ECU files a go later this week hopefully. You might be onto something there with the voltage, it seemed to take a little longer to start today, but not sure - definitely going to be making some logs of that.

[saabman]

been trying to find out more about the Lambda sensor heater resistances but nothing yet BUT i did come accross a SSP which is specifically for med9.5.1 Dropbox - SSP_322.pdf - Simplify your life

[saabman]

Just been persuing through elsawin (runs heaps better in XP) and come across this Technical product information
Dropbox - VW TPI cold start idle 1200.pdf - Simplify your life

Customer statement / workshop findings
After a cold start the engine runs sporadically for about 80 seconds at an idle speed of 1200 rpm.
Technical background
The idle speed is raised to about 1200 rpm.
Production change
---
Measure
The measured value block 56 of the engine control unit shows the actual value (field 1) and the specified
value (field 2) of the idle speed.
If the engine temperature is in the specified range and the two values in measured value block 56 are
identical the engine has no complaint.

[MEL744]

I also found that SSP the other day, doesn't look like it has anything related to this issue, but still very handy to have. Today I checked the values and they match but when its running rough there is a fair bit of fluctuation (+/- 60 rpm) around 1200 rpm as you would expect. Interesting that specifies 80 seconds which is how long it goes for when the fuel is low, but when its rough the high idle is less than 40 seconds.

[saabman]

That is rather interesting - have you checked the operation of your purge valve? It’s the only thing I can think of that would have any impact dependent on the fuel level. I’m guessing with a higher fuel level there would be more vapor passing through and saturating the carbon filter and thereby creating a higher fuel load if the purge valve was either open or stuck open.

I know mine was stuck open - i could blow through it with ease and pulling it apart I could see bits of carbon holding it open. While I was waiting for a new valve to arrive I blocked the pipe to the manifold which would have eliminated any potential effect of fuel level.

[saabman]

been contemplating the technical bulletin some more and noticed it doesnt mention the specified temperature range which has me wondering which sensor is responsible for enabling that mode and why it was occurring all through summer - of a morning the engine was around 17 deg and the oil/intake/water temps were all arround this value and of an afternoon it usually around 28-30 deg not exactly what you would could call cold temps - id love to be able to understand the opperation of the ECU better and the maps involved at engine start..
MB 130-135 are all temperature related might be worth having a look there. interestingly though I noticed inlet manifold temp can be viewed but not the temp sensor on the air filter box.

[MEL744]

Haven't checked the purge valve, but I find it fascinating that the fuel level could even play a role in this issue. So now you have changed the purge valve what happens when the fuel level is low? Does it run rough when fuel is below a quarter of a tank?

I had a quick first go at opening the maps on WinOLS today - seems like it will be a full on job to work whats going on there but will persist. Today the fuel level was around 1 notch below 1/4 and the 1200 idle for 80 seconds returned. It wasn't 100% smooth, felt like there was a few misses and even a couple more after it settled to 700 - it was noticeably smoother than normal though. My current hypothesis that at least some of the rough running is due to carbon build up throughout the intake and this is probably what I was noticing, and the rest (majority) is due to some other problem.

Given the fuel level is low and the car seems to be operating in this alternate mode I'm keen to get as much data out of it before I need to fill it up again. Current list of things that could be worth checking: battery voltage as mentioned earlier, timing data and misfire count as a means of quantifying the 'smoothness'. Any other suggestions?

Made a few logs over the past few days, haven't plotted any as for these I don't think it will be particularly illuminating - most values are constant.

First up, a cold start with full fuel
- Rough idle, 1200 rpm observed for approx 40 seconds
- 56 misfires
- Battery voltage around 14.2V

Next, cold start with low fuel
- Smoother idle, 1200 rpm observed for approx 80 seconds
- Measured temp values as requested
- Temp values all seem reasonable

Finally, hot start (car was sitting for 2 hours or so)
- Same temp values as above

From these, the temperature adaptation factor discussed earlier seems to be the same for both the hot and cold starts - so I think its just some function of ambient air temp. Also interesting is that G299 (Intake air temp sensor 2 - the one in the air box) doesn't seem to show up anywhere, might have a look for it tomorrow in case it appears in some strange measuring block. I'm thinking the 1200 rpm idle could be triggered when the difference between the 'Engine Start Temperature' (seems to be the same as Engine Outlet Temp) or some other temperature and the ambient air are below a certain threshold (close to 0). This would represent a situation where the car has been sitting sufficiently long that it has been able to reach (close to) thermal equilibrium with its surroundings and so there for will require some special procedures to bring the emissions systems up to operating temp. Time also seems to play a factor, given how if you restart it, it will settle to 800 rpm immediately. Really need the maps to confirm though.

[saabman]

You certainly get a lot more misfires than I ever noticed - mine was down around 3 or 4.

I think the misfire data is the best metric for engine smoothness as I understand It is calculated by the variation in time between ignition points.

I’m at a loss as to what to check for which is why I was doing block map scan before and after staring the engine to try and capture everything and then look for differences - unfortunately I didn’t keep track of good and bad starts to properly correlate the data.

I didn’t notice any difference between bad purge valve, no valve and good valve. Apart from the engine not reporting gas fault once the new valve went in. I’ll check with nat andcsee I she has noticed any difference between full and empty. When I had the car here for a month I only used half a tank - I don’t work far from home ( benefit of rural city living)

Logging temp values might be give some clues as to when the high idle occurs - I don’t think it should happen as often as it does.

I’m going to organize to swap cars again so I can have a play and investigate further but I’ll order some injector seals so I can get right into the valves to clean them up. Does your engine have the tumble flaps? I need to remove the injectors to get the flaps out to get access to the valves. Might try and get some crushed walnut shells and blast the valve stems to clean them up.

[MEL744]

The difference in misfire count is slightly concerning... Will try doing some block scans. Also today it threw another CEL again for the EGR so really need to check that out. In the morning it was low on fuel but idled for only 40 seconds and was rough, so I have no idea what triggers the 80 second smooth mode. Pretty sure it has the tumble flaps, not 100% sure though (haven't checked myself).

[saabman]

I think we could be looking multiple faults. I had a lok through my logs last night and could find any with misfires logged, I never bothered to log them because when ever i did look at the misfire figgures they were so low.

Maybe concentrating on the missfires might be show up something. While the TB indicates that the 1200 rpm idle is normal Im not convinced it should happen as often as it does, in you case I think the missfires is a more significant issue and my be caused by some other fault.

Maybe log misfires for all cylinders at idle, high RPM, hot cold, etc. and see if it is confined to one cylinder or effects all of them.

Heres a couple of relevant Tech Bulletins Dropbox - TPI exhaust.pdf - Simplify your life
Dropbox - TPI Missfire.pdf - Simplify your life

[MEL744]

Logged the misfires for each cylinder today on a cold start as normal. Cylinder 1 recorded 73 misfires and 3 had 1. I have replaced the spark plugs and coil packs, so will need to look into this more. Don't have the time at the moment to be taking the intake manifold off to try swapping injectors.