Power loss at speed

[robert1]

Hey

I have a small problem with my mark 5 golf GTI (nearly 125,000 miles), not much of an issue at the moment but assuming it'll get worse and it will be a problem on track days. when driving hard, so full throttle, really high revs, it drives perfectly. but as soon as you hit around 125MPH (always just above 120) you lose all power for a few seconds, like you completely lifted off but I'm really still full throttle. it stays like this for a little while, normally until you hit 100 then kicks back in, once was all the way to 80 before coming back. and other than this the car drives perfectly and no lights come on.

using a very cheap scanner I had two faults
00135 - Fuel Rail/System Pressure: Too Low
12599 - intake manifold runner control, basic setting not completed

is there an obvious thing this would be or is there quite a few possible causes?

P.S. yes I do multiple track days a year

[AJP]

You're getting fuel cuts. Classic symptoms. Your pump can't reach requested pressure, so the ECU basically backs things off until it can build up again.

What hardware and software are you on?

[robert1]

its all stock engine wise

[AJP]

its all stock engine wise

Stock map?

First thing you should be checking mechanically is the condition of the cam follower. If that's ok it might point to a failing pump. As far as I know the stock map doesn't request anywhere near the limit of the stock pump.

A remap on the other hand could be requesting too much, although unlikely at Stage 1 if it's a reputable map.

[robert1]

yes stock map, that's why I wasn't too sure.

might just replace the cam follower, not done it since I owned the car (nearly 30,000 miles) and no idea about previous owners.

I will hopefully be able to report back this weekend, thank you. didn't think about cam follower at all.

[AJP]

yes stock map, that's why I wasn't too sure.

might just replace the cam follower, not done it since I owned the car (nearly 30,000 miles) and no idea about previous owners.

I will hopefully be able to report back this weekend, thank you. didn't think about cam follower at all.

Fingers crossed it hasn't destroyed itself. That's some length of time if it's the original follower!!! I'd advise it as a matter of urgency in fact. Report back and let us know what you find.

[r5gtt]

A tfsi foeum member on FB ran his original cam follower for around 90k miles???  is that possible. not slating the fella as I'm curious as this part is meant to be life long apparently.

[lukemk5gti]

A tfsi foeum member on FB ran his original cam follower for around 90k miles???  is that possible. not slating the fella as I'm curious as this part is meant to be life long apparently.

Suppose it could be true.

Depends on driving habits.

Hammering the car means more heat, means more friction, means more wear....

He could have been a casual driver who never redlined.

Mine wasn't changed for 65,000 and it wasn't that worn when it was removed.

Previous owner was a woman working in town so just did motorway miles and no hard driving!

[r5gtt]

It could well be true as when I replaced mine at 74k ish miles it didn't look that bad now I know what I'm looking at and would definitely have gone a good few thousand more imho. I've see how bad some are when they come out and mine was no where as close to those. It's on my build thread. 2 owners before me and second was a lady owner so driving style would count for its usage and life span.

[robert1]

well mines been used on track days and driven fairly hard, so a little worrying, no idea about previous owners, I know the last was older (had a saga insurance card in the glovebox )

but the part has finally came and is being fitted in the morning, fingers crossed its not too bad and one previous owner has changed it in its life!

[r5gtt]

I really hope your cam lobe isn't damaged.
It's not the rev limiter cutting in and out is it?.

[robert1]

I really hope your cam lobe isn't damaged.
It's not the rev limiter cutting in and out is it?.

no was just a total loss of power, like lifting off throttle fully.

and its been changed, it was worn, but no hole! and it reached 130 and still pulling, so fingers crossed it was just that and was just caught in time. seems its at 125,000 miles, I can only assume the last owner changed it to, as I just reached 25,000 miles since I got it

[r5gtt]

Good you did catch it in time. 
Do you have a picture of how worn it is?.

[shoaybmakda]

i replaced mine not too long ago (mines on 125k miles now) and it was barely worn through - i guess i was quite lucky!