VW Golf 1.9 TDI (ALH) 2001- Running issues

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VW Golf 1.9 TDI (ALH) 2001- Running issues

Postby Robski » Mon Jul 09, 2012 1:12 pm

Vehicle as in the title.

The car came to me after the previous repairer had spent a week or so of head scratching & 'Googling' .

Rough running on cold start up & plenty of eye stinging smoke white in colour & stinking of un-burnt fuel, with a lack of power & general poor drive-ability complaints.

First was to plug in with VCDS to pull any DTC's (diagnostic trouble codes) which there was one of :-
17656/P1248/004680 - Start of Injection Timing Regulation: Control Deviation.

Looking at the MVB (measured value blocks) group 004 i noticed that the actual injection pump timing was too far advanced in relation to specified, with the coolant temp to 85 + i switched to basic settings to the TDI timing checker but it was that far advanced it would not plot on the graph, at this point i suspected the N108 COI (commencement of injection) solenoid stuck advanced.

I selected the output tests & actuated the N108 commencement of injection control solenoid which made the engine tone change which told me it was functioning.

I retarded the timing to a point where it started to graph & set to spec for the post 1999 ALH engine. This also got rid of the DTC.

This made a big difference in how the car drove & pulled, i tried a start after it had cooled a little & the smoke seemed better too but not exactly a cold start. I let the previous repairer take it back to try a cold start the following morning which wasn't very good to be honest & the car came back.

A check again for DTC's with VCDS revealed no codes & the timing was still in spec.

So thinking it could be over fueling on start up i adjusted the IQ (injection quantity) to trim the fueling to see if that made any difference.....No ! So we are looking at something else.

I hooked up the Pico with 600A clamp round the battery cable & did a relative compression test, as this method is non-intrusive & takes a matter of minutes rather than hours removing injectors or glow plugs to do an actual compression test.
I saw what i expected to see as the smooth running correction values were high for cylinder 3# which was adding very close to the limit of 2.0mg/stroke which indicates a weak cylinder, a negative value shows a strong cylinder.
2001 Golf ALH relative compression_.jpg

And just to back up that capture i did a compression test through Pico diagnostics
2001 Golf ALH compression.JPG

After this test i put the wire back on the N109 Stop solenoid & started the car running the cylinder balance test, this started with the one cylinder in the red but picked up quickly into the green.
2001 Golf ALH_cylinder balance_1.JPG

2001 Golf_ALH_cylinder balance.JPG


Pretty obvious now there is a problem with engine internals & when the car came the second time after a cold start i said that had it been a TDCI the first thing i would suspect was a bent con-rod ............. as it clears to an extent when warm.

It took 5 minutes to grab that information with the Pico scope in a non-intrusive manner, just another example of the the information that can be got in so little time thanks to Pico.
Last edited by Robski on Mon Jul 09, 2012 3:18 pm, edited 1 time in total.
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Re: VW Golf 1.9 TDI (ALH) 2001- Running issues

Postby Darren Cotton » Mon Jul 09, 2012 1:26 pm

Good Job Robski


Jobs like this can be a pain having more than one issue they can drive you mad, looks like you identified the second issue with good use of the scope in a reasonable time.

Did you do any more with the pico diagnostic?s the latest version has many more features on it since the last few builds...

Being a 2001 did the repair continue? as I would say it would be an uneconomical repair

Nice pictures BTW, thanks for taking the time and sharing, i bet the post to longer than the job it self :D


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Re: VW Golf 1.9 TDI (ALH) 2001- Running issues

Postby Robski » Mon Jul 09, 2012 1:37 pm

Jobs like this can be a pain having more than one issue they can drive you mad, looks like you identified the second issue with good use of the scope in a reasonable time.


They can that, & yes the Pico nailed it very quickly.

Did you do any more with the pico diagnostic?s the latest version has many more features on it since the last few builds..


No in short, i will have to update.I do try to stick to a known stable version rather than try a Beta version & get caught out in the middle of a capture :roll:

Being a 2001 did the repair continue? as I would say it would be an uneconomical repair


No not by me & i can't really see anything being done, but the Pico results quickly determined this i think.

Nice pictures BTW, thanks for taking the time and sharing, i bet the post to longer than the job it self


Thanks. No problem & yes it did :lol:
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Re: VW Golf 1.9 TDI (ALH) 2001- Running issues

Postby Alan » Mon Jul 09, 2012 3:12 pm

Thanks for that. Interesting result, even if it was not what the customer wanted to hear.

BTW on the cylinder balance you may have recorded the time when the cylinder was showing low power & in the red. Try hitting play as when you load the file back in it shows the data from the end of the test. When you hit play it shows from the start.
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Re: VW Golf 1.9 TDI (ALH) 2001- Running issues

Postby Robski » Mon Jul 09, 2012 3:16 pm

Alan

Thanks for that it never crossed my mind.

I have edited the original post to show :wink:
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