Still trying to track a suspected boost leak

Stumbled on something else last night though

I open the throttle in third, rev's rise along with maf numbers, get to about 4.5krpm, maf figure is around 140, then it drops back to 100 then back up.

Running with it disconected gives me a raise in mpg.

Is my MAF knackered, is it possible its playing up under high load, RPM because lower down and normal driving it seems fine and figures are right,

Or wuld a boost leak effect the maf figure making think its knackered. Don't really want to lay out £80 on to find that theres nothing wrong with mine.

Well Dave, I wont get too technical for you but it doesn't sound as if it's the MAF, if it was dirty I'd expect it to misread across the entire rev range, you can do a function test with a hair dryer (the hot air tricks it into allowing less electrical resistance), some can be cleaned with solvent spray, but some are knackered by solvent spray, depends if it's a wire or a foil .

Now I've sorted that for you would you like to take some of my warning points back??

Jesus where did you dig that up lol

A bird who knows what mafs do. Who'd have thought.

I'll have look when I get home at your points

Erm, shall I ring my brother in law again

Erm, shall I ring my brother in law again

ha.

Octy MAFs are wire based I think. You can try cleaning it with isopropyl alcohol. Some people have reported this can help. I changed my MAF after I bought the car (duff advise from a Westover Skoda), but the current one has done about 140k now :-)

Strange how the reading drops and that starts to rise again though....

Here is a link: http://writen4u.hubpages.com/hub/clean-replace-vw-audi-maf-diy

Here is a link: http://writen4u.hubp...vw-audi-maf-diy

this is the stupidest way to clean a MAF ... don't do it this way!

Just remove the MAF and spray it with special MAF cleaner.

Do you still have the EGR on the car?

MAF flow = Total flow - EGR flow.

EGR thought the 18t didnt have one ????

What does the above mean in English lol

And how does it apply to my issue ?

EGR thought the 18t didnt have one ????

What does the above mean in English lol

And how does it apply to my issue ?

I'm half asleep today. I was thinking Fabia VRS. If you did have one on your 1.8t it certainly would be a problem.

lol

While your there, whats the vale on the back RHS of the engine, behind the CTS, that looks to be bogging with oil ??

And I did a grab of the maf at 5-6 k rpm in third

Looks a little wierd to me, surely it would still read normally if there was a boost leak ?? figure looks a little low for WOT to me 146g/s should be more like 180-90

180 hp X 0.8 equals 144 g

Unless your car is mapped of course.

You can test for air leaks with smoke,is very good test,but is a bit odd to apply.

The idea is to add presurized smoke in the entire intake sistem,with engine off,any leak will be shown instantly.

Edited 18 August, 201213 yr by IulianE

Had a 1.8T last week, AUM engine code. Came in for a N249 valve replacement as it was showing a fault and running bad, popped that on and it ran even worse, had a look at the diverter valve which wasn't holding vacuum. Replaced the diverter valve which improved it, replaced the N75 which helped a little more but it still wasn't right.

By this time there were no codes stored and it was running like a three legged dog, disconnected the MAF and it ran perfectly.

It just shows that they can play up and not show any codes, I even looked at some readings from it earlier on in the diagnosis, which didn't give me cause for concern.

lol

While your there, whats the vale on the back RHS of the engine, behind the CTS, that looks to be bogging with oil ??

Are you talking about the camshaft adjuster?

If so, it's not uncommon for the seal to leak

Not sure lol

This one

Not sure lol

This one

That looks like the combi valve for the SAI. It has a hardpipe bolted to the engine, a large hose to the SAI pump and a small control hose to the N112 control valve.

ps/

Everything is usually described as though you are sitting in the driver's seat looking forward, so all this stuff is on the left.

That looks like the combi valve for the SAI. It has a hardpipe bolted to the engine, a large hose to the SAI pump and a small control hose to the N112 control valve.

ps/

Everything is usually described as though you are sitting in the driver's seat looking forward, so all this stuff is on the left.

Ah got you know, had been told that by my man in TPS, My combi vale is caked in oil and crap at the bottom, is there a seal down there that could be leaking and would it effect boost, bu my reckoning if it SAI related then it wouldn't.

I have a brand spanking new MAF here but I'm pondering if I fit as I have felling it's gonna be £90 down the pan !!

Ah got you know, had been told that by my man in TPS, My combi vale is caked in oil and crap at the bottom, is there a seal down there that could be leaking and would it effect boost, bu my reckoning if it SAI related then it wouldn't.

I have a brand spanking new MAF here but I'm pondering if I fit as I have felling it's gonna be £90 down the pan !!

It's more likely that the oil is getting onto the combi valve from the valve cover or the camshaft adjuster. Wipe it all down and see what happens.

Check the 'Y' shaped breather hose on the left of your picture. These are prone to splitting.

Done the Y one, thats an old picture, just been out now and the one on there is still mint, I've had the rocker gasket changed as it was seeping oil, could that be the cause of the muck on the valve ??

Done the Y one, thats an old picture, just been out now and the one on there is still mint, I've had the rocker gasket changed as it was seeping oil, could that be the cause of the muck on the valve ??

Probably, as it's very close to the corner of the rocker cover. If it was leaking, then some oil could have ended up on the valve.

Do you know anyone with a 1.8t ? It takes 10 mins to swap out have a little drive then return it to owner. Thats how i diagnosed mine, mae has a polo with same engine

Do you know anyone with a 1.8t ? It takes 10 mins to swap out have a little drive then return it to owner. Thats how i diagnosed mine, mae has a polo with same engine

BILLLLLYYY Where are you ???

He's got like a skoda garden lol

Lol soz mate. I am here oh n my mob has changed too.

Ill txt in morning.

Maf changed .......

Problem solved !!

No dropping at high rpm, engine sounds healthier all round mpg up.

Win win

and quite cheap in the scheme of things too. Good times.

When mine was changed, it ran better than ever had, so probably on its way out without me noticing. May change mine once a year