Power loss once engine warms up

[corradophil]

I now have a MkIV Golf 1.8t with an AUM engine, which is the same as an AUQ in Leon Cupras.

I had it Revo'd a couple of weeks ago, and all was well, no fault codes and the maf was peaking at around 120-125 g/s standard, and over 160g/s after the re-map. The perfomance was great.

It is now alot slower than when first mapped, the only time it is quick is when the engine is below normal running temp, as soon as it is up to temp the power drops right off.

There are no fault codes and the map still peaks at just over 160g/s.

The dv is fine with no leaks, and I can't find any boost leaks either.

Can anyone offer any ideas for what to look for next?

 

[Bogwoppit]

As a guess I would say one of you lambda sensors is on the way out, IIRC the car doesn't use the signals from the lambda sensors when it is cold but then flicks over to them when the car reaches normal operating temperature. Is there any way you can log the lambda signals?

Could be absolute rubbish but worth a thought, had the same problem on a 2001 106 GTI.

 

[corradophil]

peter0976, yes I can log them, hadn't thought of that, although I'd have expected it to show as a fault. I will do a bit more research and see what they should be reading.

 

[corradophil]

Update, whilst accelerating the power comes and goes slightly, kind of hesitating.

 

[omg!]

My LCR is standard and I get the same symptoms. It pulls well until it has warmed up to normal temperature and then it feels less willing. Unfortunately I cant find anyone with vagcom near me who can help.
Not sure if that helps you but maybe it indicates its not a remap problem.

 

[corradophil]

Hopefully if I can find the fault on mine, it may you with yours.

 

[jaime]

Sounds stupid but I've heard that sometimes you can have problems with some of the hoses when it gets warm and they start to collapse. Does it seem worse in warm weather? It could be to do with the air intake hose.

You could maybe take a look at the following link form Forge Motorsport and see if this helps...

http://www.forgemotorsport.co.uk/content.asp?inc=product&cat=1305&product=FM225IND

 

[dsrr]

'the power comes and goes' sounds like your Maf is on its way out

 

[corradophil]

Jaime, I'll inspect that pipe, although it does not appear to be effected by ambient temps.

dsrr, I have been pretty suspicious of the maf, having had one fail on the Leon I used to own, however, the symptoms were a different before and this maf is showing a good output.

 

[mitchcupra]

sensor

99% it's the sensor my leon cupra had the same problem had it on the computer an it pulled up the sensor

 

[mattbeef]

how does it feel with the MAF disconnected?

 

[corradophil]

The fuel consumption is now averaging about 7mpg lower than normal.

Still no fault codes.

It won't drive with the maf disconnected, it kangeroos all over the place, I'm guessing that has something to do with the ASP. My Leon used to drive fine with the maf disconnected, but that only had TCS.

 

[mattbeef]

Id say its could be something like the fuel pump possibly? or like has been mentioned the lamba sensor

 

[corradophil]

I've checked the Lambda sensors, and they are fine.

I've not cheked the fuel pump at the moment, but....

Last night I removed and cleaned the N75 with carb cleaner, and it made quite a difference, it's not perfect yet, but I think this is the problem.

The fuel consumption was better this morning and it is boosting better, so I'm going to give it another damn good clean up and see how it goes.

 

[Exocet]

I'll also be interested in how it goes.

I've had a similar problem occur over the last week: it's been doing my nut in as I've recently had the oil and sparks changed and all was running fine, but mine stutters on the warm up, seems to remedy itself when at normal operating temps.

oops, just seen the date of the post

 

[DPJ]

I'll also be interested in how it goes.

I've had a similar problem occur over the last week: it's been doing my nut in as I've recently had the oil and sparks changed and all was running fine, but mine stutters on the warm up, seems to remedy itself when at normal operating temps.

oops, just seen the date of the post

Your problem could be coolant temperature sensor related.

 

[Exocet]

cheers mate, I shall get that looked at

 

[Phillc]

Your problem could be coolant temperature sensor related.

If it was this would it show as a fault on vag com as i have this to but nothing showing.

 

[corradophil]

Exocet, I eventually found a split rubber hose, under the inlet manifold was causing the problems, there is a thread about it, but I can't find it, I'll have a look later when I have more time and post up a link here.

 

[corradophil]

As promised have a look here http://www.seatcupra.net/forums/showthread.php?t=116156&page=2