Solved - See Post # 7 for solution.

Hi all,

Some of you may recall that last week I had a CEL light on my Mk 1 VRS (remapped) which turned out to be 2 coil pack failures. These were replaced for 4 x geuine VAG coils, and the CEL light has not been on since.

However, I have just driven to and from Center Parcs with my family (130 miles each way), and what is glaringly obvious is that I have a nasty 'stutter' in turbo performance. :(

The problem seems to be an 'hesitation' or 'stutter' that occurs, mostly under medium boost, a sort of 'off...on....off... ON!' feeling from the Turbo. (I am confident that the problem is turbo related rather than ignition. I could be wrong on that, but it definitely feels like it's the turbo performance that is stuttering).

Here are the characteristics, facts, and background :-

• The car has 4 brand new VAG coil packs on.
  
• The car is remapped.
  
• No CEL light or other warning lights are displaying.
  
• No faults are logging on my OBDII code reader.
  
• The 'stutter' appears to be the turbo, mainly when under medium load.
  
• It feel like 1-2 seconds of the turbo going 'off-on-off-ON!' ... after which it pulls like a train.
  
• Under light load, when the turbo is doing very little, there is no sutter at all, hence it does feel turbo-related rather than ignition related.
  

Could this be a fault with the Diverter Valve? ... any other pointers?

I'd be really grateful for any help. I've seen people referring to 'coded' parts (like N75 ?) that may relate to this problem, but I don't know what those parts are?

I have read this thread :- http://www.briskoda....n-acceleration/

...but his problem does sound more ignition or throttle based - I only feel my 'stutter' when I boost the turbo. My Idle is stable and the car otherwise runs fine, with no errors logged.

So anyone willing to give me some basic points, to look at, that would be really appreciated.

Cheers.

Edited 18 May, 201214 yr by Longyear

It could be a hardware issue or it could be the remap.

Do you have anyone near you with VAG-Com that can hook it up to your car? What you need to do really is log requested boost vs. actual boost (measure block 115 in VAG-Com)

If the requested boost is all over the place then it's a problem with the remap.

If the requested boost looks sensible but the actual boost is all over the place then it's one of the following:

vac hose leak

faulty N249 valve opening the DV when it shouldn't be

faulty DV leaking boost

faulty N75 valve not controlling the boost properly

If both the requested and actual boost look ok then its nothing to do with the turbo so look at a fuelling or timing issue.

Thanks

I must admit my first gut instinct was to get the remap switched back over to the stock map, to see how the car goes then. (the company that done the remap - Elite Remaps - give a guarantee that they'll switch between stock and remapped anytime, for free, while I own the car). It does seem an obvious initial test I know. It's a bit awkward because the remapper is a friend of a friend ......... oh why or why do we never learn with these things!

The remapper has full VAG-COM so I think I'll ask him to turn off the map as a starting point, and then chat through why I'm wanting to do that, and hopefully get talking about the 'requested vs actual boost' tests above.

One other question; Do the 'N75' and 'N249' valves have any other names, other than these codes? ...... just to help if I have to end up calling a garage or specialist to discuss the problem?

Many thanks.

Edited 18 May, 201214 yr by Longyear

The problem with any remap is it puts stress on components like the N75 which can and do fail.

I've seen plenty of threads on here though about boost fluctations where people have changed all those components and then eventually found the map is to blame. Ideally when you get a remap it's good to go for a place where they do eveything on a dyno and give you graphs of things like the boost so you can see for yourself it's nice and smooth, but I appreciate not all tuners offer this.

The only other thing I can think the valves would be referred to is "boost control valves" (both of them)... the difference being the N75 in on your inlet pipework near the back of the engine and controls the boost normally, and the N249 is on a bracket on the inlet manifold and is designed to release boost via the DV if there is a problem controlling the boost the normal way.

This is a good read if you've got a spare hour or so:

http://www.briskoda.net/forums/topic/85515-the-old-hesitation-after-remap-problem/page__p__1043362#entry1043362

I would suggest that it's a good chance that it's the map. This boost surge that you talk about is common place on the 1.8t engines and a map seems to highlight the surge. I had this as did many others but Shark performance spent many hours reworking the stage one map. All is fine now.

Thank you to you both

I have just spent the last 70 minutes reading (the full) thread entitled "Do you have surge following a remap" (the one primarily about a couple of people who had a Shark remap

Wow, what an eye opener!

The problem I am experiencing is identical to what Ollie and others were describing, after their Shark remap ...... noticeable in 4th and 5th gear, mainly under medium boost (but high load). I don't feel very optimistic about resolving the problem, after reading that thread :( It certainly shows that the problems is/was not confined to Shark remaps.

I have also exchanged some texts with the guy who I bought the car from, and have found out that my car already has N249 bypass, and brand new breather pipework. At the same time as this work (Jan 2012) a new OEM Bosch DV was fitted.

As the N75 was not changed at this time, I think I will chance buying a new N75 to see if that helps.

Beyond that, I will probably just go back to a standard map.

Cheers.

SOLVED!

This is a lesson in making assumptions! ... (or rather avoiding making assumptions). In this case, me assuming that my 'problem' was the same as those in the various 'turbo surging after remap' threads.

I have just been out and unplugged the MAF sensor plug ..... the car threw the ASR light (expected), and off I went for a spirited drive: not one single stutter or hesitation was experienced. The turbo pulled clean and healthy in every gear, under every load.

In case I had imagined the whole problem, I plugged the MAF back in, reset the code, and off I went again - the first time I got into 5th gear (A19 slip road) and put the car under some load, I had massively noticeable power stuttering and hesitation.

So... knackered MAF .... sorted!

Another challenge of VRS ownership resolved..... It's never boring running these VAG 1.8T cars that's f'sure!

Cheers

Edited 18 May, 201214 yr by Longyear

Good to hear its sorted, new MAF not cheap though :(

Good to hear its sorted, new MAF not cheap though :(

Cheers, yeah :( ...... resisting the temptation to pick up an eBay cheapie, so it will be around £100 on exchange from VAG I reckon. Still, if it fixes the problem it will be worth it. ... I was tempted to leave the MAF unplugged as, as well as the lack of stutter/hesitation under load, the car was also around 15-20% faster across the board, and generally running smother. But have an aversion to dashboard lights staring at me (the missus even moreso!), so got it plugged back on for now.

It'll use more fuel with it unplugged too

gsf do bosch same as oe but cheaper still exchange i think there number is 187vg0330 maybe

gsf do bosch same as oe but cheaper still exchange i think there number is 187vg0330 maybe

Thanks mate, that exactly what I went for .... GSF .... genuine Bosch, 101 quid inc VAT .... about 30 quid cheaper that dealers, and with free delivery.