02 GT TDI 150pd juddering/loss of power @ 3000rpm

[ch4chi]

my 02 golf 150pd is giving me major problems, when it reaches 3000rpm it starts to judder (heavily) and throws out black smoke and wont go over 3000 rpm, i then have to change gears before any form of acceleration is possible, more recently their is sometimes a conplete loss of power, it then takes upto a few seconds (sometimes upto 30 seconds/sometimes longer) before it even accelerates normally in an idle state.

It also goes into 'limp mode' on motorways where I struggle to reach anywhere near 60mph!

I was told that it was my boost pipes, so I replaced 2 that a mechanic thought looked loose/worn but to no avail, took it for an mot yesterday and it failed on the emissions test!

Since the above, i have taken it to a VW specialist (VW trained) who hooked it upto the laptop, a tempreture sensor fault came up, which has been replaced, he also replaced my MAF with another one to see whether that was faulty, he then went to reset codes when a fault code came up

16688- injector 4 intrmittent misfire???

any idea's is it simply a case of replacing, or is there other possible trouble shooting i can do to rectify the fault??


Any help would me much appreciated

please take into consideration I am not very clued up on terminology or technically/ mechanically gifted when it comes to motors! So I apologise if I've missed anything or come across a but thick!!!

Thanks in advance for any suggestions

[Crasher]

I would start by having the cylinder head injector wiring harness replaced which costs around £150. As this was reported by a VW specialist I am shocked he did not suggest this, it is such a common issue with the PD.

[ch4chi]

I would start by having the cylinder head injector wiring harness replaced which costs around £150. As this was reported by a VW specialist I am shocked he did not suggest this, it is such a common issue with the PD.

I called him to say the MAF he put in to test had not resolved the issue and asked him what code came up on the VAG as he has saved the code, he checked and told me it was 16688 and that i would need to replace the injector??

Is what your suggesting also called the injector wiring looms?

[Crasher]

Yes, loom singular. With this coded it is extremely unlikely to be the injector, I would do the harness first.

[ch4chi]

thanks for quick replies, how would i go about doing this, is it something i could do myself? is there any kind of 'how to' guides or video guides available?

also how much would the harness roughly cost?

[Crasher]

You have to remove the EGR valve to allow access to one of the cam cover bolts, then remove the cam cover, if you are not experienced at working on cars, I don’t think you should attempt it. The harness costs about £50 from a VW dealer, part number 038 971 600.