VR6 Problems

[stevef 0]

My VR6 needs a new thermostat. I have looked but hav'nt a clue where it is. Can anybody help point me in the right direction.

 

Any advice on this would help.

 

While I am here - I seem to be lacking power - the engine seems to misfire at 30mph in 4th yet it idles fine and goes down the motorway fine. It does seem to fluff a little when you try to accelerate from say 70 - 80 but settles at the new speed OK.

 

Again any helpwould be gratefully received.

[Kevin Bacon 5]

In front of the radiator fan on the block is a black plastic box with 3 sensors on it, that's you're thermostat housing and inside it lives the thermostat. You have to remove the whole housing to get at the stat. You may find it easier to remove the coilpack first so that you can get to all the hoses attached to the stat housing.

 

When you get the replacement stat, get a new seal for it and also a housing-to-block rubber O ring.

 

Does the car misfire when wet? Could be the coilpack. If not, it'll be crank sensor, cam sensor, MAF sensor or O2 sensor!

 

It really needs to go on a diagnostic machine to isolate the fault.

 

Cheers

Kev

[stevef 0]

Cheers Kev.

 

Misses all the time and have run the engine in total darkness and could'nt see arcing so must be a sensor. I have re-set the ECU by removing the battery for a while with no change.

 

If I disconnect the MAF while the engine is running it makes no difference. Revs jump a little when I re-connect it.

 

Need to find somebody in Manchester who can help with VAGCOM.

 

Cheers

 

Steve

[Kevin Bacon 5]

Sounds like the MAF is dead then. A healthy one will cause the engine to almost die completely when disconnected as the ECU reconfigures itself to use the TPS. If you disconnect the MAF and nothing happens, the ECU has already bypassed the MAF.

 

Kev

[PhatVR6 0]

I'd stiff suspect the coil pack. Try spraying water on it in the dark. Examine the resin between the lead posts for hairline cracks.

[VR6 0]

I'd stiff suspect the coil pack. Try spraying water on it in the dark. Examine the resin between the lead posts for hairline cracks.

 

......if it has a coilpack (obviously :)).

[dr_mat 0]

Sounds like the MAF is dead then. A healthy one will cause the engine to almost die completely when disconnected as the ECU reconfigures itself to use the TPS. If you disconnect the MAF and nothing happens, the ECU has already bypassed the MAF.

 

Kev

 

Sounds like mine is dead too then...

 

I'll check it again someday...

[Robbo149 0]

Fast becoming the dead MAF forum?!!!!!!!! Me thinks this could be a common problem on VRs!!!

[dr_mat 0]

The latest VW engines all suffer from MAF failures too. The TDs are particularly noticeable cos they lose significant power when the MAF goes. It seems the VR6 engine masks the failure pretty well..

Now all we need to do is find a magic fix for the MAF failure epidemic!!

[Robbo149 0]

Just a quickie... I was at the local garage who work on my car the other day & they happened to have another Corrado VR6 in (with a blown head gasket :shock: ), so I had a quick shuftie at the MAF sensor on it & it looked different - mine has a square metal block, whereas this one was all black plastic, also the plug looked different to mine. Anyone know if there are different variations of the MAF sensors? perhaps down to age (mine's a '93, the poorly one was a '95).

[Kevin Bacon 5]

Just a quickie... I was at the local garage who work on my car the other day & they happened to have another Corrado VR6 in (with a blown head gasket :shock: ), so I had a quick shuftie at the MAF sensor on it & it looked different - mine has a square metal block, whereas this one was all black plastic, also the plug looked different to mine. Anyone know if there are different variations of the MAF sensors? perhaps down to age (mine's a '93, the poorly one was a '95).

 

There's two types of MAF I've noticed on VRs, late ones got the all the plastic one and earlier ones got the one with metal block on it. I believe the late ones are hot film, whereas the ones that keep fooking up all the time are the hot wire ones. I think very late 94 cars and 95 cars got the hot film job, can't be 100% on that though.

 

K

[dr_mat 0]

So how much would a "hot film" MAF cost then!?

Agreed though, the hot wire ones are fragile.

[Robbo149 0]

You are a knowledgeable chap kev, sounds like this knowledge comes from experiencing all the problems of VR ownership first hand!!?

 

Will the newer MAFs fit older VRs? or are the plugs different (as they seemed to be). If they do then it would seem a sensible mod to get the more reliable one.

 

Cheers.

[stevef 0]

My VR6 is a '95 and has the later type all plastic MAF.

 

I have booked it into a local Bosch agents for testing tomorrow.

 

I will keep you informed.

[Mike Edwards 0]

The latew MAS fits straight in - but you'll need to change the engine loom while you're at it as it has a different number of pins in the plug....

[Kevin Bacon 5]

You are a knowledgeable chap kev

 

Kind words Robbo but I'm still learning :lol: Only had the VR since Feb of this year, and it's my first Corrado and first VR engine. I like to pass on anything I learn.

 

, sounds like this knowledge comes from experiencing all the problems of VR ownership first hand!!?

 

Absolutely! Many a time I've had the engine chugging down the road with flatspots and hesitancy. This is why I bought VAG-COM, it's been very helpful. 9 times out of 10 it's an electrical problem!

 

Will the newer MAFs fit older VRs? or are the plugs different (as they seemed to be). If they do then it would seem a sensible mod to get the more reliable one.

 

To be honest I don't know mate. There's about 4 or 5 different bloody MAFs for the VR6 engine! One person that will or should know is Vince of Stealth Racing. He explained to me in great detail once (most of which I've forgotten) that all Corrado VRs are OBD1 but the Highline Golf is OBD2, which appears to have the same MAF as you spotted on that 95 Corrado. So as a guess and if that MAF is indeed hot-film, you will need the brain to go with it :cry:

 

EDIT: Ignore last part as Mike Edwards has answered it above.

 

Kev

[Kevin Bacon 5]

The latew MAS fits straight in - but you'll need to change the engine loom while you're at it as it has a different number of pins in the plug....

 

Do you change it at the MAF end and the ECU end, or just the MAF end?

 

Kev

[Dan_Storm 0]

My C seems to be running fine, but I thought I'd try disconnecting the MFA this afternoon to confirm it was working. To my surprise there was no difference in the idle or drivability.

 

I know that the ECU reverts to the trottle position sensor when the MFA dies. But my C seems to run ok apart from a slighly uneven idle (which I've just put down as the characteristic of the VR!). I haven't driven any other VR's so I can't compare it to anything.

 

So my question is, can the VR feel ok to drive (e.g. no hesitating, not idling 'too' badly, not misfiring) and still have a dead MAF?

 

I'm just wondering if i've been mising out on more power!

[Supercharged 2]

My C seems to be running fine, but I thought I'd try disconnecting the MFA this afternoon to confirm it was working. To my surprise there was no difference in the idle or drivability.

 

I know that the ECU reverts to the trottle position sensor when the MFA dies. But my C seems to run ok apart from a slighly uneven idle (which I've just put down as the characteristic of the VR!). I haven't driven any other VR's so I can't compare it to anything.

 

So my question is, can the VR feel ok to drive (e.g. no hesitating, not idling 'too' badly, not misfiring) and still have a dead MAF?

 

I'm just wondering if i've been mising out on more power!

was the car up to running temp at the time?

[stormseeker 0]

 

Do you change it at the MAF end and the ECU end, or just the MAF end?

 

Kev

 

I've discovered that the later VR6 ECUs are Motronic 2.91 (where the earlier ones are M2.8 or M2.9 ???) , and have the OE immobiliser closely integrated with them, is it just these later ECUs that use the hot film MAS?

 

Quote from a website I found selling ECUs/MAS etc...

 

==================================================================

 

BOSCH ECU == Corrado VR6 2.9 litre (ABV) ==

 

'94 on Bosch Motronic 2.91 -- 0 261 203 564 -- 021 906 258 CP (XEBM3564)

 

with Immobiliser Function.

 

These ECU`s operate as part of the vehicle's immobiliser or alarm system. In many instances they contain a code which will prevent the vehicle from starting unless activated by the vehicle's security or central locking system. In many instances it will be necesary to 'program' a replacement ECU and there may be some restrictions on testing coded ECU`s. If in doubt, refer to the vehicle manufacture`s workshop manual. All replacement ATP parts with immobiliser functions are supplied with an information sheet which should be read carefully before installing the replacement ECU.

 

=====================================================================

[Dan_Storm 0]

was the car up to running temp at the time?

 

Supercharged - Yes the car was well up to temp as the fan was coming on intermittently.

 

The only other problem I can think of is high idling (1200ish) after coming to a standstill, it returns to normal after a second or 2. It has only happened on a handful of occasions though.

 

Cheers for the help.

[Kevin Bacon 5]

I'm not so sure unplugging the MAF is a good enough test anymore as so many VRs seem to do different things when it's disconnected!

 

All I know is when mine was dead, unplugging it did nothing to the engine....but the new one stalls the engine straight away when disconnected.....bloody VR6s! Maybe it's only the hotwire ones that do this?

 

I also know that it's impossible to conclusively test on or off the car. Bosch technicians connect it to an oscilliscope and it appears normal, but the car would drive poorly. The ECU only throws a MAF code when it receives no signal at all or a short circuit, which means the MAF can still be operating out of range, but the ECU will just ignore that and not code it - and just use the TPS instead.

 

Best thing to do I guess is get it dyno'd and if it's pushing out 190 or more, it's safe to assume the fuelling is correct.

 

K

[TimVR 0]

Hi Guys,

 

I'm no expert in the field by any means - but aren't dodgy MAF sensors very bad news? Just something I learnt from Impreza website - aftermarket panel filters (oil lined) sometimes end up clogging the MAF (I believe a hot wire type) - this in turn causes fuelling problems leading to detonation and melted pistons!! The TPS may well substitute for the MAF in the VR's case but it sounds like a back up and not ideal.

 

Like I say I'm absolutely no expert and could be well off the mark - anyone else any thoughts? (Kev!!)

 

Cheers,

 

Tim

[Kevin Bacon 5]

Yeah the oil fouling is well known and I was at a Scooby garage on Saturday as it happens! My mate had a new MAF fitted to his 2000 WRX. Funny that! And coincidentally, we discussed exactly the same thing with the proprietor!

 

We all agreed that people that flood the filter with oil are the ones in danger of damaging their MAF but sensibly applied amounts of oil pose no problems. It's usually the induction kits that cause problems as the filter is a lot closer to the MAF. Panel filters and Cold air intake type kits (BMC, Turn2 etc) are fine due to the filter being a lot further away.

 

Turbo charged Subarus might suffer from melted pistons in extreme cases (usually down to the air going over the top of the bonnet scoop past 125mph) but a fouled MAF won't kill a VR6.

 

A VR will drive reasonabley OK with just the TPS but it needs the MAF for precise fuel metering. Without it, the engine runs rich.

[stormseeker 0]

Interesting you should mention Oil based air filters, but I've only had some MAF-like rough running probs since I fitted a K&N panel filter to my VR a couple of weeks ago - but mine's got the later type hot film MAF and later M2.91 ECU with integrated immobiliser... :? :? Disconnecting it & re-connecting the MAF with the engine idling produces the only slightest shudder :?