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- Nov 9, 2019
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Unable to diagnose 1998 Polo "one day no power, unable to idle, VAG-COM has no codes"
Hi to you all from a newbie in Australia
Got my shiny new VAG0COM to help me track down the problem that suddenly appeared in my Polo. I'm working through the VAG-COm capabilities but there is a LOT there, hope someone can point me in the right direction..
-----------------------------
History (1998 Polo 1.6 lkitre, auto, 6N1):
Car has 92K Kms on it, has never had a problem with running, power, starting, etc One day at startup, it had very little power, would not idle below 1100, barely moved on the road (like a dead cylinder perhaps, in the level of power reduction happening) and could go no more than ~5-10 kph, I had to select lower gears to get that too. Easily stalled out if I did not keep the revs up. I was able to move it to a place to work on it out the back of my place, but lots of stalling and nearly didn’t make a very minor hill, the power was so poor. In summary, one day with no warning (I have done my own diagnosis and repair work on many cars across every system (except transmissions) since the 70’s, I am very alert ti changes in engine function - so this was not a gradual slide into a problem, it just happened suddenly one day at startup. Very weird to be so hard to diagnose / correct....
What I've done:
Battery disconnected for a month while away. Returned and re-connected and ...
Started fine again. Runs well above ~1600rpm, it feels and sounds fine there and higher. This was what I had found myself left with before going away for a month.
If allowed to drop to 1000 rpm (taking foot off accelerator) - it hunts around across a range of a few hundred RPM, producing rough idle to smooth, engine lifts and drops rpm, gets rough, gets smooth, and so on. No obvious pattern to what is happening with the ups and downs though.
The car progressively seems to try to lower rpm by itself, this also brings increased roughness mostly. Like having one cylinder running very badly (but plugs show no issues). It then went to ~900 RPM and was rough then smooth (as if under ? ECU? control, was not consistent like if there was a vacuum leak). Then went a bit lower, hunted around again showing variously smooth then rough idling. Then a little lower and the same thing. Then after about 4 mins it dropped lower to about 500 rpm and stalled out.
But on scan with my new Ross Tech VAG-COM I get no codes at all, before or after trying things / running for a while. The battery is well charged and have tried all this after battery disconnect / reconnects, no effect.
Trying again today after being away, starts fine but drops to a very rough 600-700 rpm, sometimes up to 900, but variously rough then smooth idling. Keeps going for a few mins then dies as before.
If it was an old style carby I’d be thinking idling jets, but this is an electormechanical throttle control system.
What should I be looking at next? I’ve tried a few things, oith no change to the outcome...
Checked and cleaned the injectors (all fine)
Replaced the lambda sensor in the exhaust pipe
Spark plugs replaced (no differences in appearance to suggest cylinder issues)
Have cleaned the existing throttle body.
Tried another throttle body (wreckers).
Tried another ECU (wreckers).
Have not replaced fuel filter as that does make sense - it runs well at high rpm (i.e high fuel flow).
Tried throttle adaptation as per the Ross Tech wiki/ website video (both 001 and 098 codes, and 001 is not the adaptation code on this model), it failed to do anything, and it shows weird and very high starting values for the throttle pots:
Address 01: Engine (032 906 030 S)
10:09:10 Group 098: Throttle Control Basic Setting
128.0 Throttle Pot G69 Voltage 0.500...5.00V
119.0 Throttle Pot G88 Voltage 0.500...5.00V
53.0 Operating Mode
25.0 Adaptation Status Idle/OK/ERROR
Nothing tried with the VAG-COM with the engine “running” :-)
So, in the absence of any VAG-COm codes coming up, and the Adaptation not working, I’m a bit lost. It definitely seems like it is a throttle reset /adaptation issue not being resolved ATM, but I am new to this area.
What might the the high 098 Throttle Pot values mean for me? Any suggestions for next steps?
Thanks,
David Parsons
Adelaide, Sth Australia
Hi to you all from a newbie in Australia
Got my shiny new VAG0COM to help me track down the problem that suddenly appeared in my Polo. I'm working through the VAG-COm capabilities but there is a LOT there, hope someone can point me in the right direction..
-----------------------------
History (1998 Polo 1.6 lkitre, auto, 6N1):
Car has 92K Kms on it, has never had a problem with running, power, starting, etc One day at startup, it had very little power, would not idle below 1100, barely moved on the road (like a dead cylinder perhaps, in the level of power reduction happening) and could go no more than ~5-10 kph, I had to select lower gears to get that too. Easily stalled out if I did not keep the revs up. I was able to move it to a place to work on it out the back of my place, but lots of stalling and nearly didn’t make a very minor hill, the power was so poor. In summary, one day with no warning (I have done my own diagnosis and repair work on many cars across every system (except transmissions) since the 70’s, I am very alert ti changes in engine function - so this was not a gradual slide into a problem, it just happened suddenly one day at startup. Very weird to be so hard to diagnose / correct....
What I've done:
Battery disconnected for a month while away. Returned and re-connected and ...
Started fine again. Runs well above ~1600rpm, it feels and sounds fine there and higher. This was what I had found myself left with before going away for a month.
If allowed to drop to 1000 rpm (taking foot off accelerator) - it hunts around across a range of a few hundred RPM, producing rough idle to smooth, engine lifts and drops rpm, gets rough, gets smooth, and so on. No obvious pattern to what is happening with the ups and downs though.
The car progressively seems to try to lower rpm by itself, this also brings increased roughness mostly. Like having one cylinder running very badly (but plugs show no issues). It then went to ~900 RPM and was rough then smooth (as if under ? ECU? control, was not consistent like if there was a vacuum leak). Then went a bit lower, hunted around again showing variously smooth then rough idling. Then a little lower and the same thing. Then after about 4 mins it dropped lower to about 500 rpm and stalled out.
But on scan with my new Ross Tech VAG-COM I get no codes at all, before or after trying things / running for a while. The battery is well charged and have tried all this after battery disconnect / reconnects, no effect.
Trying again today after being away, starts fine but drops to a very rough 600-700 rpm, sometimes up to 900, but variously rough then smooth idling. Keeps going for a few mins then dies as before.
If it was an old style carby I’d be thinking idling jets, but this is an electormechanical throttle control system.
What should I be looking at next? I’ve tried a few things, oith no change to the outcome...
Checked and cleaned the injectors (all fine)
Replaced the lambda sensor in the exhaust pipe
Spark plugs replaced (no differences in appearance to suggest cylinder issues)
Have cleaned the existing throttle body.
Tried another throttle body (wreckers).
Tried another ECU (wreckers).
Have not replaced fuel filter as that does make sense - it runs well at high rpm (i.e high fuel flow).
Tried throttle adaptation as per the Ross Tech wiki/ website video (both 001 and 098 codes, and 001 is not the adaptation code on this model), it failed to do anything, and it shows weird and very high starting values for the throttle pots:
Address 01: Engine (032 906 030 S)
10:09:10 Group 098: Throttle Control Basic Setting
128.0 Throttle Pot G69 Voltage 0.500...5.00V
119.0 Throttle Pot G88 Voltage 0.500...5.00V
53.0 Operating Mode
25.0 Adaptation Status Idle/OK/ERROR
Nothing tried with the VAG-COM with the engine “running” :-)
So, in the absence of any VAG-COm codes coming up, and the Adaptation not working, I’m a bit lost. It definitely seems like it is a throttle reset /adaptation issue not being resolved ATM, but I am new to this area.
What might the the high 098 Throttle Pot values mean for me? Any suggestions for next steps?
Thanks,
David Parsons
Adelaide, Sth Australia