Volkswagen Golf IV - VW Golf TDI Lag Problems

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Mon 17 Oct 2011 17:08
Volkswagen Golf IV - VW Golf TDI Lag Problems - vanurdi010310

VW GOLF GE TDI PD 150 - 139,000 miles

I have just had the top half of my engine rebuilt as the Cam Shaft had worn. At the same time the garage changed the Head Gasket, Cambelt, and skimmed the head. They found when they test drove the car there was no power till 4,000 revs. All 4 injectors were
then changed. They then said everything was fine.

When I got the car back I found there was no pull/power till 2,000 rev. The car used to take off like a rocket in low revs as it had been remapped. Also in 6th gear around 70MPH the pull has reduced and so has top end speed.

Is there anything else that could need changing or could be at fault/damaged like delivery of air, fuel or engine management ect? The car had a remap about 5 years ago so could this be the problem after the rebuild?

The car also need 2 attempts to starts at the moment.

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Mon 17 Oct 2011 19:38
Volkswagen Golf IV - VW Golf TDI Lag Problems - outlier

No power below 4000rpm.. sounds like racing cam behaviour :-(

Could you do compression/leak down test to confirm mechanicals?

Maybe there is a way to confirm turbo boost pressure.

I am also wondering how specific the engine remapping is, i.e. if it was tuned specific to your engine as it was, not as it is. Or if it has lost the settings altogether.

Suggest you post this to the technical forum...

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Mon 17 Oct 2011 21:33
Volkswagen Golf IV - VW Golf TDI Lag Problems - craig-pd130

The PD diesel relies on the camshaft to actuate the injectors. In effect, the injectors on this engine work a bit like a syringe, the camshaft pushes the "plunger" to pressurise the fuel, then the injector solenoid opens at the right time to start combustion.

If the camshaft timing is even slightly incorrect, the injectors will not work properly because they will not be delivering fuel at the expected pressure. This would explain the poor performance and poor starting.

The fact you've had the head removed and the cam replaced suggests to me that the garage has NOT set the camshaft timing correctly -- they may have it one tooth retarded on the cambelt. I'm not certain but there may be adjusters on the camwheel too to dial in the timing correctly.

I'd suggest checking this first before looking elsewhere.

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Mon 17 Oct 2011 23:06
Volkswagen Golf IV - VW Golf TDI Lag Problems - Avant

Moved to Technical.

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Mon 17 Oct 2011 23:24
Volkswagen Golf IV - VW Golf TDI Lag Problems - vanurdi010310

What about things like:-

MAF sensor N75 Valve Vacuum Hoses/Reservo

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Mon 17 Oct 2011 23:39
Volkswagen Golf IV - VW Golf TDI Lag Problems - 659FBE

Well - here goes:

Briefly, the PD system uses an extra lobe per cylinder on the overhead camshaft to actuate a plunger in the unit injector (PD) which pressurises the fuel. When the engine requires its precisely metered shot(s) of fuel, a solenoid (early, reliable models) valve is energised and the fuel is injected. Solenoid off - no more fuel.

Although the phase relationship of the camshaft to the crank (KW in VAG speak - Kurbel Winkle = Crank Angle) is obviously important, the crucial injection timing is derived, as it should be, from the crankshaft via a tone wheel inboard of the flywheel. It follows that as long as KW lies within a fairly generous tolerance allowed by VAG, pressurised fuel will be available for injection over the required operating map of the engine.

The camshaft wheel on the PD is adjustable relative to its hub so that KW can be set - and it can also be read electronically via the diagnostic port. It is therefore possible to see if the belt has been wrongly fitted without actually touching the engine.

If KW is in error by a small amount (from memory, about +/- 3 degrees) it can probably be corrected in-situ using the wheel slots in the camshaft wheel. If not, the belt has been fitted 1 tooth out and the job will need to be done again properly.

A PD will run 1 tooth out - but not very well.

659.

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Tue 18 Oct 2011 12:15
Volkswagen Golf IV - VW Golf TDI Lag Problems - craig-pd130

If the camshaft has been replaced, I'm not sure if the new cam will actually be supplied with the camwheel fitted -- which means the old one may have been fitted to the new shaft and not set up correctly.

Even if it is a complete shaft / wheel assembly, it may not be set optimally.

I also wonder if the PD150 motor uses a different cam to the PD130, and if the replacement is definitely the correct cam ...?

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Tue 18 Oct 2011 13:00
Volkswagen Golf IV - VW Golf TDI Lag Problems - vanurdi010310

The Cam was for PD 150 ARL engine. The Pulleys were also replaced.

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Tue 18 Oct 2011 15:06
Volkswagen Golf IV - VW Golf TDI Lag Problems - vanurdi010310

So far from the replies I have got it could be any of:-

MAF Sensor
N75 Valve
Vacuum Hoses
Bad Timing (Slack Tensioner or off by tooth)
Turbo Boost Pressure/threshold
Cam Wheel not setup correctly - may have one tooth retarded on the cambelt
Cam Timing sensor broken
PD injector wiring loop damaged or wasn't plugged in correctly

I have been told to run the engine for a week or so to let everything bed in and then take it back. Is this a good idea or could it do more damage.

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Tue 18 Oct 2011 15:43
Volkswagen Golf IV - VW Golf TDI Lag Problems - craig-pd130

It's unlikely to do any damage but equally it's unlikely to improve from 'bedding in'.

If it isn't actually stuttering or misfiring, it's unlikely to be a wiring loom problem.

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Sun 17 Jun 2012 22:46
Volkswagen Golf IV - VW Golf TDI Lag Problems - gidyon06
did you manage to get to the bottom of the problem dude as i have the same problem
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Tue 19 Jun 2012 15:09
Volkswagen Golf IV - VW Golf TDI Lag Problems - craig-pd130

Have a read of this article, about the effects of tiny changes / adjustments to the cam timing on a PD motor.

http://autospeed.com/cms/title_Big-Changes-from-Tiny-Adjustments/A_112521/article.html

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