Hello everyone,

Took the 1.9 TDI 110 elegance (61000 miles) to the garage today to get them to look into my turbo issues. Basically the turbo seems to have a mind of its own and stops working and will sometimes get back to normal on restarting. Most seem to this it could be a sticky turbo.

The garage performed a diagnostic check. 2 faults. MAP (Manifold Absolute Pressure) sensor failure and turbo overboost. The mechanic looked at the wiring going to the MAP. Some of the wires looked a bit frayed and were rubbing against each other. His remedy was to stick some tape round the wires. He then said that this had cured both faults (I had my doubts on this). I started to drive home and the turbo failed to respond when I tried to overtake a caravan 10 miles down the road so I drove back to the garage.

He then did a test and said that the MAP problem had reoccured but that the turbo overboost fault had gone (???). The remedy is a new MAP sensor which will be fitted next week. Can the MAP have such an affect on the turbo performance and does it sound like the sort of fault which when remedied would cure the turbo overboost fault? I can't see how I had two faults this morning and just one now!!!!

Any advice/thoughts would be greatly appreciated!

The idea that you could get bad readings from the MAP sensor, leading the EMS to conclude that you had overboost is basically sound, if there is a MAP failure mode such that it could read higher than actual manifold pressure, and that was compared with a good pre-turbo MAF sensor reading.

Thanks very much Ken. Much appreciate the response.

Where does the MAP sensor hide?

I'm generally pretty clueless on cars so here's my basic description!

It's just a small box which when you open the bonnet will be on the drivers side very close to the front of the vehicle. The mechanic had to remove front light etc to get close to it. It's got some sort of wiring to it (wiring has a loom sleeve around it). My wires within the loom now have some tape round some sections!!. After that, I'm not sure where everything is linked!!!!

Ken will know a lot more than me!!!

I didn't think the Octy had a MAP sensor. If it had one, I'd expect to find it top back, under the obsfurcation cover, for the reported diagnosis (which is what my theory was based on) to make sense. Although it could be in the RHF arch, next to the intercooler.

The MAP sensor or more aptly named boost sensor lives either in the top of the intercooler or on the main boost pipe leading upto the intake.

A manifold pressure fault can be logged if it doesnt see a pressure it expects to. i.e and overboost situation due to a sticky turbo.

Thanks Lummox. Could you clarify the post?

I'm interpreting that I could have a new MAP but still have the sticky turbo!

Thanks again,

Gareth

That's exactly what Ross meant. And he's also explained why I didn't think there was a MAP sensor; I'd associate that term with non-turbo cars.

Help folks!

Well I had the MAP sensor fitted. All went swimmingly well for about 2 weeks. Now the car (0252 1.9TDi elegance) has gone into "idle" turbo mode 3 times in 2 weeks.

Could this be an indication of an MAF issue? The last occasions it has gone into idle mode when the rev meter reaches about 3000 in 3rd gear.

Thanks again,

Gareth

I think we're looking ar either a sticky turbo, an MAF or an N75 issue?

Many thanks Ken. Much appreciate the response.

Is the N75 easy to check visually? The car is booked in for next Tuesday but I'm just being curious? The MAF's also easy to spot isn't it?

Thanks,

Gareth

Just to give an update. Might help those who are experiencing "limp mode".

Took car back to garage this week. Car was going into limp mode at around 3000 revs in 3rd going up hills.

Vag Com came up with code 17965. They think did further checks. The problem? The VNT actuator was jamming under load and only became operable when restarting car. Car's under warranty so a new turbo is going on tomorrow. Many thanks for all your help and ideas.

So its a sticky turbo then.

Suprise, not.

Indeed, and my first thought once we'd a known good boost pressure sensor too.