Golf Mk4 ALH shaking/smoking on first hard press of accelerator on cold start

[golffan68]

Hi,
I hope someone can point me in the right direction with a problematic car. I have a Golf mk4 1.9Tdi, ALH engine. Recently, the turbo blew and was replaced by a VW/Audi specialist. Some weeks later the pipe came off the turbo, but was re-inserted. Some months have elapsed and If I start the car cold, it easily starts and ticks over as normal on idle. However If i give it one short push on the accelerator pedal, it immediately starts shaking like it's misfiring. It's quite a severe shaking as well. At the same time it starts blowing a lot of greyish smoke which smells.
I realised this problem after a few occasions of driving when i'd try to accelerate and this would happen until I restarted the car. After a few occasions, I'd figured out the pattern and I can reproduce it as described above.

The only way I can drive it with a functioning turbo is by letting it warm up, otherwise it experiences this problem every time I try to join a dual carriageway and have to press hard on accelerator.
To avoid this shaking/ smoking, I've disconnected plugs to MAF sensor, turbo solenoid and EGR solenoid. This allows me to drive it but without turbo.
First thoughts was EGR, so cleaned it and with no change took the vacuum line off the diaphragm nipple, blocked it with screwdriver and still no change.
I've checked for vacuum leaks and there appears to be none, diaphragm on EGR is fine and doesn't drop pressure, checked movement of wastage actuator with mityvac and its moves freely.
I've also checked resistance on engine temp sensor and it is within range. Checked MAF with a new spare and no change. Checked all 3 solenoids (N75, EGR and EGR bypass) and they all appear to function correctly.
If anyone has any ideas or what I could check next, I would really appreciate the advice. PS: It is due for a timing belt change, in case that is important.
Thanks

[micheal balbrig]

Probably best to see if a scan shows up anything,initial thought was glow plugs but second thoughts with your information seems to say it is
something else.

[golffan68]

Thanks Michael,
I did suspect the same for a moment, but since I can reproduce this problem every single time and avoid it by disconnecting electrical harnesses as described earlier, I discounted glow plugs. I'll get it scanned as you suggest rather than mess around with it. It is quite a puzzle though

[niall campbell]

back to basics

change fuel filter in case the filter has water in it and its freezing the diesel

For all the price of glow plugs, I would change them ............................. its put the ignition on, let glow plug light go out, wait 2 seconds and then start car . All year round ..............exrends life as the glow plug is still heating up after the light goes out

[golffan68]

Thanks Niall, Thats now two people who've mentioned glow plugs. I think I will change them especially as I've never had to change them in approximately 80k miles. Before I do, I might just get resistance off them, just to satisfy my curiosity. Also, you mentioned fuel filter, but I got that changed when I did a major service and it didn't improve things. The problem also happens on a nice warmish day, again when the engine is cold. Might change it anyway, since its such an easy, inexpensive thing to change. Thanks for the suggestion.

[grant19841]

Plug in to vcds for codes to save spending on parts unneeded.

You could also check the injector wire harnes as these are know to have split wires, and check the injector plugs.

Is the car shuddering or shaking?

If it is more of a shudder then you could check the anti shudder valve to see it is not stuck open.



Good luck

Sent from my SM-A300FU using Tapatalk

[golffan68]

Thanks Grant,
Shudder, Shake...it feels and sounds like both. The ASV is open as normal during running, but does close as intended when shutting down the car. I've arranged for VCDS codes to be read and will report back with findings. Thanks for the suggestions so far