Got a flashing glow plug light on the display and the car went into 'safety' mode while driving up the M1 yesterday, after the long speed-limited section to Northampton. Took it to the dealership where I was going while I did the various meetings etc, and then went back to collect. They could not find anything on the diagnostics and the light was no longer going on, so said I should be OK to get back. About 20min into the drive back, the light goes on again. I stop at the service station and have a coffee, get back to the car, and lo and behold, the light is off again. Get to Luton, and then it goes on again. Stop, turn off the engine, start again and its fine!

 

Anyway, after a while a saw a pattern. It seems to go on when I accelerate strongly in 5th gear and there is a degree of incline in the road. If I accelerate gently, it's OK. Also accelerating in lower gears also seems to be OK. I do not want to waste hours and £s talking it to the dealership to be told they cannot find anything but having the problem recurring. Any suggestions very welcome. The car has had the emission upgrade. Have seen some posters with similar problems suggesting lose connectors, lose or cracked air pipes, sensor errors etc.
 

Edited 1 February, 20206 yr by ReneR

Assuming there's nothing wrong on the wiring or vacuum systems. I'd be suspecting the variable vane linkage (VNT) on the turbo's got a bit gunked up. If you look up the "Mr Muscle" method of cleaning it, you'll get plenty of hits for how to clean it out with some oven cleaner. 

Thanks Steve, much appreciated. I'll take a look. Funnily, I was thinking it might be something to do with the turbo. I don't feel it kicking in like it used to when accelerating.

Spot on!

 

It needs an enema, the other thing that can cause the same problem I had years ago on a 1.9TDi Alhambra was degradation of the vacuum pipint to the actuator caused by the turbo heat, the pipe when heated could collapse internally sealing the pipe and the turbo actuator would gradually release, I think there must have been a tiny leak also for this to happen, it would happen under the circumstances you describe especially when towing.

 

Sticking vanes usually manifest during the warm up period, you have to drive gently till engine fully warm then usually giving it the beans causes no problem.

It's also worth taking the boost hose off after the turbo and having a look to make sure the EGR valve isn't sooted up . Unlikely to be that, but it did give me slight problems in addition to the VNT when I had my ibiza. If it is, there's various methods of cleaning it,

Thanks guys this is very helpful. Only problem is that the photos of the Mr Muscle technique I found on the forum are all fuzzy. I'll look around further. Sounds pretty straight forward from the text.

A friend with a VW with a TDI 1.6 engine also suggested to check the MAF sensor and sent me some instructions how to do so. Worth checking? Difference was that his glow plug light would come on after a restart, but he thought it may just be a partial failure and hence the indicator light not flashing all the time.

Well, FWIW I was also thinking "overboost error", which suggest a VNT, MAF or MAP issue (dependent on engine and turbo).

A delayed update on this post in case it is of use to other users, plus a possible sequel to it to run past people.

 

The original intermittent flashing glow plug indicator and limp mode problem eventually cleared up, as suggested in the replies to my post, by one bottle of Wynn's Turbo Cleaner additive into a full tank of fuel and running of that fuel till as close to the end of the tank load as possible. Engine performance much smoother and fuel efficiency slightly better for some time after the fault alerts stopped, but the improvements gradually wore off. The problem, however did not recur. 

 

Fast forward a year to last weekend and on the way through the start-stop traffic on the A23 in South London, flashing glow plug indicator comes on again during?/after? a regen, but due to in-town driving, no perceived loss of power/limp mode. Drive home and when I restart the car to drive it to the garage, the yellow/orange Exhaust System Control light (with the shape of an engine) comes on too. My local independent VAG garage, who are generally trustworthy, found a (turbo?) boost pressure fault (can't remember the code) but then spent ages trying to find what was causing it because all seemed OK. I asked whether it might be the turbo and they said the had tested it and it was OK. Through a process of elimination they have concluded to replace the air intake pipe from the turbo and also the turbo pressure sensor, if I remember/understood well. The thinking was that the air inlet pipe might have a difficult to spot leak and the sensor was dirty so may not be working as needed. They also suggested, as on inspection the air inlet had substantial carbon deposits, to run a carbon clearing process on the engine that will remove residues all the way from the fuel intake to the tailpipe and everything in between.

 

It seems that the fault reports have now stopped with the fix suggested. I am relieved to not have to fork out for a new turbo or EGR valve or cooler (which was what I was worrying the problem might relate to), but just wondering if anyone has any thoughts about this and if the course of action suggested sounds plausible. 

Edited 3 March, 20215 yr by ReneR

On 03/03/2021 at 16:55, ReneR said:

It seems that the fault reports have now stopped with the fix suggested. I am relieved to not have to fork out for a new turbo or EGR valve or cooler (which was what I was worrying the problem might relate to), but just wondering if anyone has any thoughts about this and if the course of action suggested sounds plausible. 

 

It will be interesting to know the outcome of this. I had similar symptoms in our Roomster nearly five years ago now which eventually became permanent due to the failure of the EGR valve. The valve and cooler are one unit and is a reasonably involved job to change being situated up the back of the engine. So hopefully you don't have to go down that route! 

On 07/03/2021 at 10:07, HeavyMetalRich said:

 

It will be interesting to know the outcome of this. I had similar symptoms in our Roomster nearly five years ago now which eventually became permanent due to the failure of the EGR valve. The valve and cooler are one unit and is a reasonably involved job to change being situated up the back of the engine. So hopefully you don't have to go down that route! 

Pleased to report that the fault was cleared and the engine is running well. While removing the engine air intake pipe from the turbo, the pipe - which is plastic - actually broke into many pieces, so it appears it was in a bad condition despite the apparent lack of a visible hole upon initial inspection. The actual fault itself was reported as incorrect reading from the turbo air intake sensor.

 

Engine definitely feels smoother now and car was driving well during a 70km drive in the motorway and up and down some pretty steep country lanes over the weekend, but cant say I feel a very noticeable improvement from the carbon clearing process and fuel use as per the car computer is pretty much as it was.

The pipe had probably been sucking air then. That's turned out not too bad for you, I hope you get many more trouble free miles!

3 hours ago, HeavyMetalRich said:

The pipe had probably been sucking air then. That's turned out not too bad for you, I hope you get many more trouble free miles!

Yes, I hope so too! It's getting on now in terms of mileage (120k) and years (nearly 10) , but I like the car and its is perfect in terms of size and space for two adults and two kids plus luggage doing long trips. Struggling to find anything new that fits our needs in the same way, so have decided to hold on to it and take the hit with repairs as it gets older rather than fork out on a new car. Hope I don't regret the decision. The garage said that it should have a new lease of life now with the carbon cleaning and new air intake and sensor. Generally use the car for long trips and hardly ever in town, so hoping that will keep the exhaust control system in reasonable condition.

 

The only previous serious issues I had were a cracked EGR cooler (fixed under guarantee) and an injector failure due to the dodgy electrical insulation issue, which I had to pay to repair. Also had to replace the alternator. Think these two areas of faults are the ones that worry me most in terms of possible recurrence with TDI engines. Its a very well thought through car with a unique design and look and I like using it, so fingers crossed that it makes it till the kids leave the nest without too many big ticket items to repair.

2 hours ago, ReneR said:

Yes, I hope so too! It's getting on now in terms of mileage (120k) and years (nearly 10) , but I like the car and its is perfect in terms of size and space for two adults and two kids plus luggage doing long trips. Struggling to find anything new that fits our needs in the same way, so have decided to hold on to it and take the hit with repairs as it gets older rather than fork out on a new car. Hope I don't regret the decision. The garage said that it should have a new lease of life now with the carbon cleaning and new air intake and sensor. Generally use the car for long trips and hardly ever in town, so hoping that will keep the exhaust control system in reasonable condition.

 

The only previous serious issues I had were a cracked EGR cooler (fixed under guarantee) and an injector failure due to the dodgy electrical insulation issue, which I had to pay to repair. Also had to replace the alternator. Think these two areas of faults are the ones that worry me most in terms of possible recurrence with TDI engines. Its a very well thought through car with a unique design and look and I like using it, so fingers crossed that it makes it till the kids leave the nest without too many big ticket items to repair.

 

Yeah I completely agree about the Roomster being one of those cars that are just so practical with the amount of space in the size of car. And because they have their own niche, they're difficult to replace.

 

Our one, the power steering failed, I think it had been on the blink for a few years before it gave up completely, so I had to replace the pump (I did the pipes too as they were rusty). Then on the way home from getting that sorted, an injector gave up. The bill for that two (just parts) and the salesman from the dealerships I work with showing me a Karoq Scout that my partner fell in love with, sealed the Roomster's fate. 

 

Ours did a lot of its mileage a half a mile at a time over eight years, so the adage that short journeys are the death of diesel engines isn't always true!