110 TDi hesitation / misfire - help please

[starbiscuit]

The elsaweb links are pretty comprehensive thankyou.

The pic does look like my layout. EGR housing (#18) includes vacuum actuator and a disc valve on a rod.

I'm currently running with N18 and MAF disconnected. I prefer the lower acceleration and smoother running to the missing and cutting-out.
Once I get the MAF cleaned or replaced, I'll check and clean the N18 and EGR, then dial it out with VAG-com and clear the CEL. I don't think there's much point sorting the EGR with a duff MAF.

Seems to consensus on here is that Bosch MAF is the only way, rather than Euro Car Parts own brand. However, they are a lot cheaper and just up the road if I have an issue.
Do I risk it?
Or is best advice really "only use Bosch"?

Thanks again,
Rob.

 

[Seatmann]

You could try this, I found it on the tdi club as I spend way to much time there lol.


So maf mod

You put your thumb nail in where the white arrow is and push the tab in the direction of the red arrow, this releases the locking tab and the plug can then pull off.

Anyway I got some of this

And sprayed it in here

I put the plug on and off a few times then left it to dry for a few minutes. Once that was done I then took this

And squirted it in here

and here

Then I did the same again with the plug, on and off a couple of times, added a bit more of the dielectric grease and finally fitted the plug for good insuring that the lock was fully home.

Try that for the maf, be very careful trying to clean inside as you can ruin them. When my egr was acting up I got the occasional kangaroo mode lol. With it taken out of the equation though my car is a lot smoother. I did the simplified vacuum set up keeping the asv but getting rid of the egr.

Test the maf under load too with your vagcom

http://www.myturbodiesel.com/1000q/a4/MAF-sensor-testing-VW-cleaner.htm


Cheers

 

[Pimped up vario]

This picture of a TDI 110 engine bay indicates the EGR valve as no. 18.

I think that matches your description? The disc contains the diaphragm that moves the EGR valve itself.

The tube going to the egr valve in my ASV leon was blanked off with no problems caused by it. This was from about 20000 miles to 75000 miles. Went through MAF's like nobodies business. At least three. My cordoba has a pierburg MAF, made in switzerland.

 

[Seatmann]

The tube going to the egr valve in my ASV leon was blanked off with no problems caused by it. This was from about 20000 miles to 75000 miles. Went through MAF's like nobodies business. At least three. My cordoba has a pierburg MAF, made in switzerland.

Yours is the AHU though? So you could just stick a diode in the maf plug and be done with it.

 

[Pimped up vario]

What does the diode do? Apparently the pierburg MAF's never fail.

 

[Muttley]

If I remember correctly, Pierburg made the OEM MAFs for some engines.

Starbiscuit, the consensus of opinion gathered from the forum is that "cheap eBay" MAF's are never reliable and that you should always buy OEM. Given that MAF problems are often difficult to diagnose, I'd much rather spend the money on a part you can expect to be good.

 

[starbiscuit]

Hi Seatmann,

The electrical contacts on my MAF look good. There's no damp or corrosion or crud.
Great pictorial guide, BTW. Is that a non-Bosh MAF?

The problem with my MAF is that it probably has 100,000 miles on it. I certainly cannot ever remember having it changed and I've had the car since 2005.

So there's a good chance that the heater element part is clogged. I have some IPA aerosol and will try cleaning before just replacing.

But the other complicating factor is that the plastic latching pip that locks the connector onto the MAF is broken. So even if I can resurrect the MAF by cleaning it, I would have to glue (or otherwise bodge) the connector onto it to stop it coming loose

Any views on Bosch / non-Bosch MAF?

PuV - I've heard elsewhere that Pierburg MAFs are OK. GSF do them I think.

 

[Alan G H]

Most people who know will tell you only to use a genuine MAF. With regard to the EGR valve, I run a toledo with the AHF engine, and have had the EGR valve blanked off for the last two and a half years, with no problems. I made a blanking plate to fit in the joint between the pipe up to the valve from the turbo, but you could just pull the vacuum pipe off the top of the valve and screw a self tapper into the end of the pipe to seal it to try it. It has not put the engine warning light on, and the EGR valve operation is not checked at the MOT test, so, if it works on yours, no worries!

 

[Seatmann]

What does the diode do? Apparently the pierburg MAF's never fail.

The diode tells the ecu that there's plenty of air and just gives you full pelt apparently. Doesn't seem to work on the newer cars with the bosch maf.

If I remember correctly, Pierburg made the OEM MAFs for some engines.

Starbiscuit, the consensus of opinion gathered from the forum is that "cheap eBay" MAF's are never reliable and that you should always buy OEM. Given that MAF problems are often difficult to diagnose, I'd much rather spend the money on a part you can expect to be good.

It was the Mk3 golfs etc and the same age seats all used the pierburg Muttley

Hi Seatmann,

The electrical contacts on my MAF look good. There's no damp or corrosion or crud.
Great pictorial guide, BTW. Is that a non-Bosh MAF?

The problem with my MAF is that it probably has 100,000 miles on it. I certainly cannot ever remember having it changed and I've had the car since 2005.

So there's a good chance that the heater element part is clogged. I have some IPA aerosol and will try cleaning before just replacing.

But the other complicating factor is that the plastic latching pip that locks the connector onto the MAF is broken. So even if I can resurrect the MAF by cleaning it, I would have to glue (or otherwise bodge) the connector onto it to stop it coming loose

Any views on Bosch / non-Bosch MAF?

PuV - I've heard elsewhere that Pierburg MAFs are OK. GSF do them I think.

There's some sort of theory that the very fine electrical signals can jump between the pins and that non conductive silicone is supposed to help. Some people report an amazing difference and it's only a couple of quid for the grease off ebay so well worth a try. As for the connector being broken just wrap a big cable tie right round the whole thing and strap it on.

http://www.ebay.co.uk/itm/Dielectri...al_Components_Supplies_ET&hash=item588fd87e66

Try it. If it doesn't do the job then buy a new one but only a bosch one as said and you only need the actual sensor, not the complete housing.

I think this is the part number you want but a quick google will confirm it.

 

[Muttley]

The Pierburg is a hot-wire MAF from the earlier cars. I'm pretty sure my Mk.2 Ibiza TDI 90 had a Pierburg MAF. Hot-wire is a bit more robust than thin-film.

The hot-wire or thin-film MAF is a very clever answer to the thorny problem of measuring *mass* flow rather than flow velocity. It uses the same technology developed for fuel flow sensors in aircraft, many years ago. I know this works and is a solid and reliable method for the task.

The MAF is not "safety-critical" and so is not monitored to the same level as, say, the throttle or engine speed sensors are. It's only used to fine-tune the fuel delivery, turning OK performance into hey, that's nice.

The thin film MAF is sensitive to contamination and is bound to accumulate deficiencies even if good attention is paid to proper servicing intervals and air filter changing.

A useful teardown of a MAF element is described in this thread

http://forums.audiworld.com/showthread.php?t=1491569

More detail from myturbodiesel

http://www.myturbodiesel.com/1000q/multi/maf-faq-tdi.htm

This is a mildly exotic sensor element that can cause annoying performance blips as it gradually fails. I think that, for peace of mind, it is well worth paying the extra for an OEM part.

 

[starbiscuit]

So I finally bought a new MAF sensor to replace my questionable one.
I saved up my pennies and got a great deal from the nice folk at GSF in Chelmsford.

I swapped out the whole MAF assembly in the end, not because it was particularly dirty (it wasn't) but because the sensor-only options were suspiciously cheap unbranded, or non-OBD. I guess you can't go far wrong swapping Bosch for Bosch...

Anyway, I reconnected N18 EGR connector and the MAF connector and the car runs great again.

Now I just need to clear the fault codes from running without EGR+MAF. And maybe dial-out the EGR with VAG-com.

Thankyou to everyone that has read and contributed to this thread.

Cheers,

Rob

 

[Pimped up vario]

Good stuff. Glad your running 100% again.