Hi everyone.

I've just recently purchased a VW Golf 1.9 GT TDi 115 (AJM) second hand with 112K miles on the clock. The engine runs really sweetly and I am totally chuffed with the car. I've never owned a TDi (or any diesel for that matter), so I'm completely new to the game. Before the Golf, I was an avid VW Polo fan, and I've just sold my beloved supercharged G40!

I'm enjoying the Golf, as it feels much more solid and is an absolute dream to drive, but I have one relatively minor niggle which I've just noticed, that I need to get sorted.

The problem occurs in any gear, but is more obvious in the lower gears. Basically, at a specific throttle position, the car will sort of hesitate or surge as if I was gently increasing and decreasing the throttle position, at a frequency of about once a second.

With the window wound down, I can hear the turbo spool up and down when the problem is happening. It will only do it in a certain throttle position, which is at about 1/8th.

After a bit of experimenting, there are two ways in which you can stop it. Either slighly increase the throttle and the turbo will spool up fully and pull away as normal, or you can let it do its thing, then after about 5 seconds it stops the hesitation.

There are no other problems I can detect, i.e the turbo pulls very strong throughout the rev range, in an gear. It's almost like the turbo isn't sure whether it should spool up when I feather on the throttle!

I've just got hold of a VAG-COM, which I'm going to look at tonight and I've just done a full service, which included air filter and fuel filter, but the surging still remains. As I mention, these engines are completly new to me, so I'm hoping someone can shed a bit of light and give me some clues as to where I should start investigating.

Thanks in advance guys.

check the vac lines for any splits/blockages and check the boost control solenoid.

dunno if theres a measuring block for this but that will be worth a go too seeing as you have vagcom

 Having a few issues with the VAG-COM at the moment, so unfortunately can't do a scan yet. Could you point me in the right direction to find the boost control solonoid?

Thanks for your reply.

I had a very similar problem on the V5 and ti was a partially blocked fuel filter. Cheap fix :)

 Unfortunately, I've already replaced the fuel filter, and air filter for good measure, but still the same symptoms.

I want to test it with the MAF unplugged, but I need to see if it has thrown a CEL before I unplug it.

I'm hoping it is the MAF, as that would be an easy and cheap(ish) fix.

Sounds similar to the problem I had. It was an issue with the EGR. I've just disconnected the vacuum pipe to it and bunged it up. No more hesitation.

Could be worth a try.

 Thanks for the hint. I think I'll give that one a go tonight then. Is the EGR that little diaphragm that sits on the driver's side of the throttle body?

Chris-J:

 Thanks for the hint. I think I'll give that one a go tonight then. Is the EGR that little diaphragm that sits on the driver's side of the throttle body?

yes. it's not a throttle body either. diesels don't have throttle bodys. it's an anti shudder valve all it does is shut when you turn the engine off and stops the engine shuddering a little bit.

 Of course, sorry, I'm still in petrol mode. I believe only the later engines have this anti-shudder valve?

Anyway, I'll remove the vacuum to the EGR and plug the hose and see if that helps.

Do you know whether these engines have a wastgate, or is the boost controlled through fin angle? Just wondering whether I should check the wastgate actuator for issues, if there is one.

 It's a Variable vane turbo so no wastegate.

Just take the egr out completely and clean it out and put it back in.

Chris-J:

 Of course, sorry, I'm still in petrol mode. I believe only the later engines have this anti-shudder valve?

yeah all the mk4 tdi's had anti shudders fitted.

Chris-J:

Anyway, I'll remove the vacuum to the EGR and plug the hose and see if that helps.

permanently, the EGR does nothing but block up your inlet manifold. screw the environment!

Chris-J:

Do you know whether these engines have a wastegate, or is the boost controlled through fin anglevariable vanes? Just wondering whether I should check the wastegate actuator for issues, if there is one.

yes as baz said they are variable vane turbos, and they have a boost control solenoid(as i refferred to in post #2 ^^^^)

it's far right on the bulkhead(click for pics), check the hoses up to it and all the way to the actuator, and check the actuator see if it holds vac.

also whist your there wiggle the VNT mech and see if it moves freely. it is quite stiff normally and requires a bit of force but it should move all the way up and down. pics of the VNT mech/actuator here

so to sum up

• disable the EGR
• check the boost control solenoid;
• and all the vac lines;
• and the actuator for damage/leaks/faults.
• and leave the anti-shudder solenoid and lines in place they do no harm

and for good measure heres a map of the vac lines.

Really appreciate all your help with this guys. Disabled the EGR and problem has completely disappererd. Well diagnosed!

Drives sooo much better now, and seems a bit more responsive too.

So I take it this valve has just totally gunked up then, causing it to malfunction? Do you think it's worth popping if off and cleaning it (along with intake) or just leave it now that it is disabled?

yes it's worth a clean, remove the intake manifold and EGR and clean them with degreaser allow to dry then re-fit .

have a look at these pics here

 What never ceases to amaze me is the way car manufacturers never put things like this on the service schedule. In my eyes, if you're going to make the engine breath it's own farts for emissions control, then it should be brought to the attention of the owner that this system is in place, and should be checked and cleaned at regualr intervals.

It's only now that the EGR system has failed that I'm aware it's there. I'll bet when I take it apart, it's going to look very similar to those pictures you posted.

Regarding gaskets, am I ok just renewing the inlet gasket, and re-using the o-ring and gaskets on the EGR?

i would renew the inlet manifold gasket they are only a couple of quid. the o-rings can be re-used and the egr gaskets can be re-used if your careful. they are only fibre and they stick to the bottom of the EGR very well and might snap if you pull them off too agressively

i doubt your egr will even be half as bad, that is an extreme case. theres some more pics here that will be what it looks like probably