slight loss of power and lower MPG?

[andrewcoley]

Hi all

I've got a 54 plate Ibiza Cupra TDI; completely standard.

It seems to me to be slightly less responsive the last couple of weeks, on initial throttle movement in particular, turbo maybe coming in slightly later. Still goes very well at higher RPM but sometimes having to come down a gear where before the turbo would have done the work.

Also noticed it's lost a couple of MPG, on a tank of mixed motorway/A Aroads it doing 44/45 ish, where before it was 47ish usually. No change in driving style.

I've read lots of EGR valve threads, as well as various sensor replacements, split hoses etc but am at a bit of a loss as to where to start, as the problem isn't serios enough to point to anything definate; still fast, no weird smoke, not awful MPG, not going into safe mode. I did wonder if it was just me being very used to the car (maybe just in head, doesn't 'feel' quick any more) or the warm weather taking the edge off it?

No VAG com but could get basic fault codes read if necessary if this wil point to a quick solution rather than take apart and clean job? Sorry I know this query is super repeated, have searched forum but nothing definitive. If there is an FAQ / order of checks for this fault please point me in right direction.

Thanks, Andrew

 

[SteveC123]

All VAG TDIs suffer with the MAF failing periodically, and this normally doesn't show up on VAG-COM, so you may find it's this.

In my experience, hot weather does take the edge off the performance - you get 'heat soak' building up in the intercooler, especially around town etc.

Also, it might sound a bit daft but if you're filling up on a really hot day, fuel like most fluids tends to expand in the heat, and you're not actually getting quite as much fuel as you think for your money once it cools of an evening etc, and contracts.

That, and a fuel that has expanded due to heat will not have quite as much calorific value in it per millilitre etc, and that might help to explain the feeling of power loss?

I could of course be talking bull... but that's a few things that might be worth considering as contributory factors.

 

[andrewcoley]

Thanks for that steve; if MAF had failed would symptoms not be more serious/obvious?

Had a quick look at the easily visible pipes last night; the elbow pipe that runs into the EGR valve was not flush, sticking out at back a little, though no oil around the area. Removed it and had a good look; one of the two 'notches' that the retaining clip attaches to is badly worn (the 'back' one) and so the pipe is not as secure as it could be.

O ring seems OK and as mentioned no oil, but I'm wondering if anyone has had a similar issue with the clip locator being worn or if this would be enough to maybe cause a slight loss of power?

Regarding my previous post, went for a drive last to check, turbo is first noticeable at under 2000 rpm, boost is strong from 2-2500 upwards, so not suspecting this so much now?

Actuactor rod is very free.

Any more help appreciated. Thanks

 

[sssstew]

no mafs die slowly and rarely log faults. The only way to tell if they are performing badly is to log requested vs actual airflow with vag com.

 

[aBoijj]

no mafs die slowly and rarely log faults. The only way to tell if they are performing badly is to log requested vs actual airflow with vag com.

Can you log those at the same time with the free version of vagcom? I got a cable the other day but I've not had chance to use it yet.

 

[sssstew]

yep should be fine. references :-

http://www.ross-tech.com/vag-com/cars/tdi.html

needs block 3

Shareware limits :-

http://www.ross-tech.com/vag-com/tour/logging.html#Shareware

allows you to log block 3