Ignition Timing at Idle (Vag-com question)

[Ice White Socks 0]

Hello,

 

Had some trouble with the VR after fitting a new Cam Position Sensor, basically it has lost some of its sensitivity and flexibilty at part throttle- sometime you feel like the more you press the throttle the slower the engine goes. I have checked absolutely everything obvious- the car still has all its power at full throttle, Vag-com is clean, no pinking, ISV cleaned, car idles fine etc etc.

 

The only thing that caught my eye was the ignition timing field on Vag-com at idle. The correct value is supposed to be Six degrees BTDC which mine averages at. This value updates on Vagcom- every second or so and mine jumps like 6, 3.8, 5.9, 6.8 etc never goes below 3.8 or above 6.8 but jumps around quite a bit- is this normal?

 

Cheers

[kebabman 0]

Mine varied between 5.8 and 6degrees, I didn't see any of the low or high figures you are describing. ;)

[stevemac 0]

Theory -

 

The 6.8 that you register may indicate that or your timing is too far advanced & the "knock sensors" are telling the ECU to retard the timing, hence the fluctuating figures ?

[Kevin Bacon 5]

Yeah it does jump about a bit.

 

For a more informative picture of your timing, use the log function and record the timing over a 20 minute drive (from cold).

 

Fire up the measuring blocks (engine running), move to block 001 and hit the 'log' button, then 'Start' (you can change the file name if you wish).

 

After 20 min run, load up the outputted *.csv file into Excel, go to the top row of the data and go to 'data', 'Filter', then select the 'Autofilter'.

 

On '001' column, go through the rpms and check the timing against the rpms. Any wild variations could indicate the ECU backing the timing off.

 

As an idea, mine averages 6.3 BTDC at idle and 38.3 BTDC at 6000rpm.

[Ice White Socks 0]

OK two more things I thought about yesterday:

 

1) I checked the blue Temperature sender from cold to hot- that looked fine but I remember the EGR temp reading 180 degress before I even started the engine- could this sensor affect ignition timing??

 

2) The car stalled twice yesterday on startup which makes me think maybe ISV sticking somewhere- one of the measuring blocks indicates the ISV function soomehow (on idle mine read 54%) could i use this measuring block to indicate an ISV problem?

 

Cheers

 

Mike

[Kevin Bacon 5]

Ignore the EGR (Exhaust Gas Recirculation), it's an American feature n/a on UK cars.

 

I don't think you can do anything with the ISV on the measuring blocks. I'll check at lunch as the laptop is in the car.

It shouldn't cut out when cold though!

[Ice White Socks 0]

I'll check at lunch as the laptop is in the car.

 

Cheers for that mate- much appreciated- be good to know what your ignition timing ranges between at Idle.

 

Great call on checking the timing vs revs using the log function as well :D

[Kevin Bacon 5]

Yeah it's cool, you can log any of the measuring blocks and then load them into VAG-SCOPE (or excel) and see what's occuring over time.

 

It's not a way of isolating specific faults, but if the timing for example is doing weird things at certain rpms, it points you in the right direction at least.

 

I'll have a play at lunchtime and see what the idling parameters are like.

[Ice White Socks 0]

Well I think I might have cooked up a theory for this problem. When I had the engine in bits checking for vacuum leaks and loose plug leads etc, I also noticed an irregular knocking from the left hand side of the engine- I think this is the belt tensioner- its not grinding or squealing though- it knocks every one-two seconds.

 

I reckon this is being picked up by the knock sensors and retarding the ignition- I can't think of another reasonable explanation- I'll get it changed and see what happens :roll:

[Kevin Bacon 5]

Could be, although I think the Knock sensors are tuned to a specific frequency...and that is a guess before I get attacked for giving bad advice!

 

Best way to check the tensioner is to slacken the belt and spin the pulley by hand to see if it's stiff or grindy. If it spins freely with no appreciable lateral play, it's OK.

The other thing that can rattle down there is the water pump.

 

BTW, my timing at idle remained at a constant 6.3 degrees during warm up but when hot it fluctuated between 4.8 and 8 degrees, so not dissimilar to yours. At WOT the timing was 38.3 degrees. I don't know if those figures are right though as I don't know what the timingshould be!

 

I'll be sending the logs to Vince over the weekend and he can tell me for sure.

[Ice White Socks 0]

Kev, I have always found your advice to be spot on mate (if your referring to the 'other' thread there). I would be interested to hear what Vince says about your ignition logs anyway. I think I'm just clutching at straws with the knock sensors- Its just frustrating when your cars runs like a bag of spanners without any obvious reason why :-(

[Kevin Bacon 5]

Thanks mate.

 

I'm in the same boat with the rough running. I have ordered a new Intake air temperature sender (screwed into the manifold above the thermostat hosuing) as I've found the idle quality is a LOT better and the engine is smoother when this sender is disconnected, so I think it's shot. It's worth a try anyway.

 

Try it on yours. If the engine runs even worse with it disconnected, it's OK. But again, you can log the intake temps over the period of a 20 minute drive. The temp should be high when sat in traffic and drop when on the move. Mine was sat at 20 degrees permanently, not a good sign!

 

I'll let you know if the new IAT sender makes any difference or not.

 

What's your MPG like? If it never gets above 25mpg, something is amiss.