TDI MAP & MAF Sensors

Cupra Kid

Has a TDI!!
Oct 13, 2005
3,380
1
Chesterfield, Derbyshire
Hi Guys

Got a TDI 110 ASV thats having occasional limp modes. I've had the turbo cleaned and replaced the vacuum lines and also the N75.

So that kind of leaves the MAF or MAP sensors. Which one would most likely cause limp mode and what are the best aftermarket brands as I don't feel like spending the cars value on dealer parts.

Cheers

Paul
 

Muttley

Catch that diesel!
Mar 17, 2006
4,987
31
North Kent
I'd suggest getting a reading of any fault codes using VCDS before you go any further - that should help to tell you which way to go.

And I'd endorse the recommendation for OEM parts: try GSF or ECP or Dave at Sere Motors here on the forum for some better pricing.
 

Cupra Kid

Has a TDI!!
Oct 13, 2005
3,380
1
Chesterfield, Derbyshire
Getting readings for overboost, however the vnt is moving as it should. Puzzling thing is it can do it at anytime not just when the engine has high load so that to me suggests its more of a faulty sensor.

I think there may also be a possible boost leak which I will get looked at too.
 

Israar

Active Member
Dec 8, 2014
450
4
Dudley
Cupra Kid, where did you go for your vacuum pipes mate? I still have intermittent turbo boost but I'm not getting any codes up, though I have as Muttley found out an Audi N75 valve on mine instead of the original. We found out that the mechanic who blanked my EGR valve off (by plate) changed it due to the problems I was having when my old Turbo VNT was sticking, replaced the original one with the Audi one to see if it made a difference. He never replaced the original and when I went back for it a couple of months afterwards he couldn't find it so might have gone in the trash.

I've had my Turbo done, EGR blanked off, 2 split pipes replaced (although more do seem to need doing as they are original and frayed) so I more than likely have a leak which is why mine might be intermittent (or the N75).

Hopefully you can get yours sorted out with as little fuss as possible! :)

--Lee
 

Muttley

Catch that diesel!
Mar 17, 2006
4,987
31
North Kent
To be honest, CupraKid, I'd look at your EGR valve first, as that is a known problem area, and one that comes on gradually, and manifests itself as overboost. Basically, the EGR valve sticks open when it should shut again (at high revs), letting exhaust pressure into the inlet and causing overboost and so limp mode.

The cause is sticky carbonised sludge formed from the hot, sooty exhaust hitting the oily crankcase vapour that the PCV system puts into the inlet airstream. This coats the EGR valve itself and the inlet manifold, everything downstream of the EGR valve in the inlet system - eventually the inlet becomes choked and performance drops off as well.
 
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Cupra Kid

Has a TDI!!
Oct 13, 2005
3,380
1
Chesterfield, Derbyshire
Cupra Kid, where did you go for your vacuum pipes mate? I still have intermittent turbo boost but I'm not getting any codes up, though I have as Muttley found out an Audi N75 valve on mine instead of the original. We found out that the mechanic who blanked my EGR valve off (by plate) changed it due to the problems I was having when my old Turbo VNT was sticking, replaced the original one with the Audi one to see if it made a difference. He never replaced the original and when I went back for it a couple of months afterwards he couldn't find it so might have gone in the trash.

I've had my Turbo done, EGR blanked off, 2 split pipes replaced (although more do seem to need doing as they are original and frayed) so I more than likely have a leak which is why mine might be intermittent (or the N75).

Hopefully you can get yours sorted out with as little fuss as possible! :)

--Lee

Hi Lee, got them from ebay, they are just fuel cotton braided fuel hose cut to size. You can use 3mm silicone pipes but I wanted to replace like for like.

Paul
 

Cupra Kid

Has a TDI!!
Oct 13, 2005
3,380
1
Chesterfield, Derbyshire
To be honest, CupraKid, I'd look at your EGR valve first, as that is a known problem area, and one that comes on gradually, and manifests itself as overboost. Basically, the EGR valve sticks open when it should shut again (at high revs), letting exhaust pressure into the inlet and causing overboost and so limp mode.

The cause is sticky carbonised sludge formed from the hot, sooty exhaust hitting the oily crankcase vapour that the PCV system puts into the inlet airstream. This coats the EGR valve itself and the inlet manifold, everything downstream of the EGR valve in the inlet system - eventually the inlet becomes choked and performance drops off as well.

My EGR is blanked but it could still be an issue, for the reasons you've mentioned the system is caked in muck. Why VW vent the crankcase back into the inlet system is beyond me!

Rain stopped play with it this weekend, so hopefully next one it will be nice enough to have a day with the socket set and a load of cleaner.

TBH I'm getting towards the end of my patience with it so hopefully it will be sorted soon before it becomes an Ebay special. Shame its a great car when it works!
 

Muttley

Catch that diesel!
Mar 17, 2006
4,987
31
North Kent
Pretty nearly every engine now has a positive crankcase ventilation system, because the ill-thought-out, single-minded, emission control regulations say you can't emit unburned hydrocarbons to the atmosphere, and crankcase vapour contains oil droplets.

So they vent them into the inlet, meaning for them to be burned in the cylinders - that should be simple enough, eh?

Later, another set of regulators come along and say you can't emit nitrogen oxides either, they are Evil (tm) © ® Smog Precursors and Must Not Be Formed, so you can't let your combustion gases get too hot. Never mind that that reduces thermal efficiency, you must reduce the oxygen content of the charge so it doesn't get so hot. Never mind if it causes a bit of soot for now.

And so on, through DPF's and three different kinds of catalyst in the exhaust system. Next year's lot will find something new to demonise, maybe red paint or excessive tyre noise - anything to let them think they are making a difference...
 

Cupra Kid

Has a TDI!!
Oct 13, 2005
3,380
1
Chesterfield, Derbyshire
Well I guess if they are being forced by law then you cant really blame the manufacturers, however VW have been doing this for years and all it does is congeal over all the moving parts in the inlet affecting performance. I'm not sure much of it gets back into the cylinders as it just fills the pipework, diverting it into the inlet pre-turbo is positively stupid though!

So the lack of heat is why the turbo vanes get clogged up and eventually pack in all together, regulation is literally killing cars.

I bought the Toledo thinking that with the earlier diesel engine it would be less complicated as the PD's suffer more with clutch wear and injector issues - doesnt seem to be so.

Thankfully I still have my simple MK2 Ibiza Cupra so as soon as I have fixed everything to allow me to sell it with a clear conscience I'll be going back to that.....

... shame really its a great car when there are no niggles.
 

Israar

Active Member
Dec 8, 2014
450
4
Dudley
Hi Lee, got them from ebay, they are just fuel cotton braided fuel hose cut to size. You can use 3mm silicone pipes but I wanted to replace like for like.

Paul

Thanks Paul! :)

I'm looking to go down the silicone route but doing my entire pipe work, having changed ideas all the while though.

I definitely want them doing due to some of them being frayed badly (EGR one culprit but it's blanked off) but my plan is to stick to either all black or 3 difference colours. Similar to the hand drawing I did when I made my post about the vacuum pipes! :)

Hope you can get yourself sorted out soon though fella!

--Lee
 

Muttley

Catch that diesel!
Mar 17, 2006
4,987
31
North Kent
If your EGR is blanked off then you shouldn't be seeing any further buildup of debris. But cleaning the valve and manifold out will probably transform the car. The EGR is the only big issue with older VEP engines, and usually you can get away with just disconnecting the electrical connector from the N18 valve - the older ECU's don't put up an EML for that, and it stops all EGR action.

In later cars you can still usually turn the EGR down to almost nothing, which is almost as good.

The VNT vanes in the turbine section will soot up on any diesel that is mostly driven short distances and at low speed - the turbo never gets hot enough to burn them off. The Italian Tune-up works wonders in most cases, but make sure your engine is in good condition, oil up to the mark and so on.
 

Cupra Kid

Has a TDI!!
Oct 13, 2005
3,380
1
Chesterfield, Derbyshire
Thanks Paul! :)

I'm looking to go down the silicone route but doing my entire pipe work, having changed ideas all the while though.

I definitely want them doing due to some of them being frayed badly (EGR one culprit but it's blanked off) but my plan is to stick to either all black or 3 difference colours. Similar to the hand drawing I did when I made my post about the vacuum pipes! :)

Hope you can get yourself sorted out soon though fella!

--Lee

Yeah I toyed with replacing them all with silicone but wondered with them passing over the inlet and exhaust manifolds whether they would take the heat, so make sure you get the high temp resistance stuff. The widths vary over the lengths of pipe work, 5mm at the N75, 3mm at the turbo actuator and elsewhere, but silicone is pliable enough to get it to fit snug.

You can also go for a simplified vacuum system removing the N18 valve (EGR Control) if you google it you'll find it. If yours is a 90 or 110 tdi you won't get error lights for removing it, but if its the later PD engine I believe it will throw one up.

Mines decided its happy to tool along again at the moment, been driving it harder at the sacrifice of about 5mpg and it seems to like it as only had a couple of limp modes this week when going downhill :confused:

A VAG specialist has recommended this Forte Diesel Turbo Cleaner and its got some positive comments too so going to order a couple of bottles and see how it gets on. Also going to pull the inlet apart and clean it out along with the sensors and reseal as I can hear some air escaping.

Also going to try and work out a way to subtly divert the crankcase vapours out of the inlet and into the atmosphere...... I'll plant something to make up for the additional hydrocarbons!

Garages won't touch the turbo though, spoke to all the local ones and all they are prepared to do is replace it for around £500.......... which happens to be the cars value so that's not happening.
 

teeburn12

Active Member
Dec 13, 2013
49
0
bolton
I definitely want them doing due to some of them being frayed badly (EGR one culprit but it's blanked off) but my plan is to stick to either all black or 3 difference colours. Similar to the hand drawing I did when I made my post about the vacuum pipes! :)


--Lee[/QUOTE]

I may be reading this wrong but if the vacuum pipe is frayed it will still cause issues even if the egr has been blanked off the vacuum pipe is still part of the system and needs to be sealed.
 

Cupra Kid

Has a TDI!!
Oct 13, 2005
3,380
1
Chesterfield, Derbyshire
I definitely want them doing due to some of them being frayed badly (EGR one culprit but it's blanked off) but my plan is to stick to either all black or 3 difference colours. Similar to the hand drawing I did when I made my post about the vacuum pipes! :)


--Lee

I may be reading this wrong but if the vacuum pipe is frayed it will still cause issues even if the egr has been blanked off the vacuum pipe is still part of the system and needs to be sealed.[/QUOTE]

Yes you need to terminate the connection so there is still a sealed vacuum. There's a T joint on the main line to the N18 that you can take out and replace with one uncut pipe.
 
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