02 GT TDI 150pd injector issue????

**ch4chi** · 13-02-2010,06:22 PM

Hi,

I have posted on here a few times regarding issues i am having with my golf 150PD, brief background- the car intermittently judders and throws out smoke @ 3000rpm and at other times it just flies!! I changed the MAF, checked boost pipes and changed 2 of them but to no avail.

Anyway recently whilst on the vagcom it came up with the foillowing fault:

16688- injector 4 intermittent misfire

the mechaic changed the injector with 2 other injectors, both of which made no difference, today he changed over my injector 3 with injector 4 (as we knew that 3 was fully functioning) as well as changing the injector wiring loom, yet it still comes up with the code????

please help???

thanks in advance.

**Crasher** · 13-02-2010,06:43 PM

If the code says the misfire is still on 4 even with a different injector in there, it makes me think you have a mechanical issue in the form of a worn cam follower and damaged camshaft. This is extremely difficult to see unless you remove the camshaft.

The other possibility is that the cam is worn on the injector arm lobe, I have seen this many times. This can be seen after removing the rocker arm.

One point though, the seals and bolts for an injector MUST be changed if the injector is removed and if the seals were not changed, they may be damaged. If the bolts are re-used, they may snap when being tightened up to the 12 Nm and turn 270° (3/4 turn) further spec or if they are not tight enough, the injector can come loose and destroy the head and injector, which will really upset your bank manager…

**ch4chi** · 13-02-2010,06:55 PM

the current mileage is 92k, the camshaft was changes in january 08 at 81k???

I am pretty sure (positive) no seals or anything were changed when they took out the injectors, but they are VW specialists nd have done similar work for many years??

Other thing is that they took out my injector (number 3) and changed it with injector 4, that was showing a fault, after they put it back together the fault still only came up for injector 4, so if the seals or bolts were not changed on either injector, shouldnt a fault code come up for both injectors 3 and 4?

**Crasher** · 13-02-2010,06:59 PM

The damaged cam in the second picture was changed 10K and 18 months before it failed. This was due to the people who changed the cam not fitting new rocker arms and I have seen this problem with the code you have many times, if you are not looking for it, it is easy to miss. I suggest you get them to pop the cam cover off and remove the rocker shaft for cylinders 3 and 4 then rotate the engine to inspect the injector lobe.

**ch4chi** · 13-02-2010,07:06 PM

do the symptoms i have listed seem consistent with camshaft damage? main problem being the car juddering and smoking at 3000rpm, its almost as though its hit a wall and cant accelerate past 3000 rpm?

**Crasher** · 13-02-2010,07:11 PM

The car the cam in the second picture came out of had the same fault code as yours but for cylinder 3 I think (the DTC’s for Mr Byrns car are on the works server) and it was missing, spluttering and running like a sick dog, belching smoke, running on three until just off idle and generally not a happy bunny!

**ch4chi** · 14-02-2010,03:31 PM

Originally Posted by Crasher

The car the cam in the second picture came out of had the same fault code as yours but for cylinder 3 I think (the DTC’s for Mr Byrns car are on the works server) and it was missing, spluttering and running like a sick dog, belching smoke, running on three until just off idle and generally not a happy bunny!

so what exactly do you suggest i tell the mechanic to look at?

i suggested the ecu harness (going from injectors to ecu), so he suggested checking that, then the ecu, then compression test on the engine, to see whether there has been any damage to pistons?

**Crasher** · 14-02-2010,05:13 PM

The code you have is defined by VAG as

16688 (P0304) Combustion fault detected, Cylinder 4

1) No combustion in cylinder 4
2) No compression

I suggest they remove the cam cover and inspect the number 4 injector lobe on the cam and also check the valve lobes to see if they look damaged but as I said, cam follower (tappet) wear is difficult to see without removing the cam. I have had plenty of head harnesses fail although you have already changed that but I have never had the main ECU to head harness fail but it is possible. If it was an electrical fault the code I would expect you to get is

17679 (P1271) Valve for injector pump cylinder 4 -N243 - Regulation limit not reached

and/or

18077 (P1669) Valves for injector pump cylinder 4 -N243 - Electric fault in current flow

Possibly together with the 16688 code you are getting.

I have a rule that serves me relatively well, it is never the ECU or wiring. I does not hold true in all cases but ECU failure is extremely rare, I have had to replace only one PD ECU ever and that was for a completely different fault that I have heard is relatively common.

**ch4chi** · 14-02-2010,06:07 PM

dont know if this helps, nut this morninng the car wouldnt start, hd too jump start it, and it was smoking heavily for around 15-20 minutees, even when idle, it seems to be able to go over 3000rpm more easily (not juddering or heavily smoking, as it used to do). But it kicks into 'limp home mode' when i am trying to give it a blast?

**ch4chi** · 14-02-2010,07:59 PM

Sorry to sound like prat, but i am a novice, is there any links you could provide as to how the injectors and cam shaft are related? what i mean is how can one affect the other? how close to one another they are situated, etc...

even a description, but a picture link will help me understand it in more detail.

thanks