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Go Back   TDIClub Forums > TDI Model Specific Discussions Areas > VW MKIV-A4 TDIs (VE and PD)

VW MKIV-A4 TDIs (VE and PD) This is a general discussion about A4/MkIV Jetta (99.5-~2005), Golf(99.5-2006), and New Beetle(98-2006). Both VE and PD engines are covered here.

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Old February 13th, 2009, 03:45   #1
poor1
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Default Mk4 Golf Excess smoke at cold start

I have a 1998 Golf TDI Mk4 bought new and synthetic oil changed every 5000 miles. New air filter and fuel filter. Current done 64,000 miles and changed MAF at 52,000 (two years ago - not doing a big mileage).

Just checked pipes around the inlet manifold and everything looks OK. Last I looked inside the inlet manifold it had no more than a light coating and certainly not clogged up.

When MAF was last changed (genuine VW Part)there was a pronounced drop in performance, accelerating in particular. After changing it it drove like a new car.

Recently started pumping out excessive smoke from the rear exhaust when starting from cold, but clearing as it warmed up. Disconnected MAF and started from cold - no smoke at all. Reconnected MAF and still no smoke.

Reasonably confident fault lies with the MAF, or at least the signals it is giving to the Engine Management System. Have ordered a a new MAF.

Is this the right diagnosis?

On reflection it could be due entirely to a bad connection between the plug and socket of the leectrical connection, despite an electronic lubricant being used.

Last edited by poor1; February 13th, 2009 at 06:24.
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Old February 13th, 2009, 09:20   #2
jettawreck
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Quote:
Originally Posted by poor1

On reflection it could be due entirely to a bad connection between the plug and socket of the leectrical connection, despite an electronic lubricant being used.
Very possible/logical conclusion. One more, of several, possible causes could be the fact that your TB has stretched a bit and retarded the injection timing. Cold starts are generally a bit better/quicker with the timing advanced, so if its a bit "late" and you crank a bit longer, it loads up a little extra fuel that when it fires up is expelled out the exhaust as smoke (unburnt fuel). Get it hooked up to the VCDS and graph the timing to see where its at. Has the TB been changed and what is current miles/km??
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Old February 13th, 2009, 14:32   #3
poor1
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Many thanks for your considered response. Good to have confirmation on a line of thinking. Current mileage 65,000. Changed the timing belt at 40,000 (3 years ago)and made sure the dynamic timing was spot on. I'll hook up and check it again. The performance had been excellent since I changed the MAF for the first time at 52,000 (2 years ago).
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Old February 14th, 2009, 03:38   #4
poor1
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You're right the dynamic timing has dropped back (retarded) a little to 48 t0 50.
Additionally a fault did show up on the MAF showing P1144 - 35.00 "open or short to ground". Fitted a new MAF and after clearing fault showed "no fault". I would appear that my theory of there being a bad connection might have been partially correct.
So I think the principle problem seemed to be the MAF, but I will take on board the retarded timing question and adjust it in due course.
The main thing for the time being is that the smoke problem seems to have gone away. If you have any observations regarding the faulty MAF readings I would be interested.
Many thanks too.
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Old February 14th, 2009, 06:10   #5
conate
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I had the same problem a few months back and believe it or not I cleaned my snow screen and the smoke was drastically reduced.
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Old February 14th, 2009, 07:12   #6
jettawreck
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Quote:
Originally Posted by conate
I had the same problem a few months back and believe it or not I cleaned my snow screen and the smoke was drastically reduced.
If it (snowscreen) was clogged up some, that isn't surprising.
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2001 Jetta TDI GLS Silver-current driver (salvage)permanently vented-Panzer Plate-Sprint 520s-ScanGauge-CheckTemp III-ZeroStart heater-CAT 2 filter
2003 Jetta GLS Black w/leather (New Project Car) fixer-upper w/broken TB
2004 Cadillac SLS (wife's)
1999 GMC Suburban (It's MN-you need one)
197? Shibura 2cyl diesel 4WD tractor-loader/brushhog (very handy unit)
196? International TD340 Dozer-w/Drott 4-in-1 bucket/back ripper attachment
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Old February 14th, 2009, 10:44   #7
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Run a can of Lubro Moly Diesel Purge through it. Worked for me. Injectors probably a bit dirty and not giveng a proper spray pattern.
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Old February 14th, 2009, 15:19   #8
poor1
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Thanks I will. Every little helps.

As regards the dynamic timing, from what I understand, so long as the timing point (on the vertical line)remains between the two top and bottom lines on the graph at a particular fuel temperature (shown along the horizontal line) the timing point is acceptable and there is no need for adjustment. As the timing point on my Golf is well within the graph lines there is no need for the timing to be changed.

Last edited by poor1; February 15th, 2009 at 04:34.
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