stumped

[KADVR6 0]

can anyone help me PLEASE, no matter what gear im in, and whatever rpm, as soon as i put my foot down my car judders 4 a few seconds, then the revs pick up and all is fine?? any help is much appreciated. :scratch: :(

[vr6storm 0]

coil-pack,fuel filter/pump,HT leads,loose ECU feed plenty of other stuff it could be..................best get someone to VAG-COM check it 1st for the sensors as you could be chasing yer tail all day trying to rule them out......good luck :wink:

[dr_mat 0]

Could also be timing, tappets, fuel grade, maf sensor .... The list goes on.

[CazzaVR 0]

Dr mat beat me to it- was gonna say maf sensor. The exact same thing used to happen on my first VR until I got the maf sorted.

 

My current VR is a bit juddery and jerks a bit when you lift off the throttle- mostly in the lower gears. Reckon the maf is probably pretty dirty. Don't want to risk giving it a clean in case I damage it :?

[dinkus 10]

You can test the MAF...

 

Start the car up and let it idle for a min or 2

 

Unplug the MAF

 

If it immediately starts coughing and spluttering then the MAF is OK, so plug it back in.

 

If nothing at all happens, then your MAF is dead and that'll be another £150 please.

[dr_mat 0]

Funnily enough, very late VR MAFs don't have this effect on the engine if you disconnect them. There's no noticeable difference to idle on disconnect, but the engine hiccups slightly when you reconnect it, that's all.

[dr_mat 0]

Could also be your throttle position sensor, by the way.

You really need to get VAG-COM to take a look if there's any error codes reported.

[Kevin Bacon 5]

Funnily enough, very late VR MAFs don't have this effect on the engine if you disconnect them. There's no noticeable difference to idle on disconnect, but the engine hiccups slightly when you reconnect it, that's all.

 

That's precisely what OBD1 MAFs do when they're dead :? ECU detects "something" being plugged in, out of range, ignores it, carrys on as normal.

 

OBD2 MAFs are no different in operation and Vince reckons the hot wire ones are actually a lot more reliable than hot-film ones, which doesn't say much for those really does it as the wire ones aren't especially robust.

 

Oh and unplugging a late MAF does cause the engine to shut off if it's new, cause I tried it on a 33K Storm......

[dr_mat 0]

Then there's a lot of dodgy MAFs out there... *

 

 

* - that don't show up as faulty on VAGCOM.

[Kevin Bacon 5]

Certainly seems that way......

 

The ECU is only concerned about the physical connection and won't say anything if the CFMs are out of range, which is very handy!

 

Some OBD2 ECUs have MAF monitoring, which is very useful as any silly CFM readings will instantly give the game away.

[pablo_vr6 0]

had the same prob - also MAF

[CazzaVR 0]

Anyone know a safe way to clean the maf :?: I'm assuming my car is still on it's original maf, which means it's covered over 200K- must be pretty grimy by now.

[dr_mat 0]

The ECU is only concerned about the physical connection and won't say anything if the CFMs are out of range, which is very handy!

 

Weird thing is the mode of failure - surely if the ECU was ignoring the MAF it would throw a fault code?

 

Empirical evidence seems to suggest otherwise, but it's stoopid. grrr

 

But it would explain why my VR does so poorly in fuel economy compared to some..

[Kevin Bacon 5]

Anyone know a safe way to clean the maf :?: I'm assuming my car is still on it's original maf, which means it's covered over 200K- must be pretty grimy by now.

 

You don't need to clean it if it's a hot wire MAF (metal block on MAF tube) as it has it's own cleaning cycle. It heats the platinum wire to 1000 degrees for a second when you turn the engine off, which burns off any contaminants.

 

It is *very* delicate.... so I would avoid the usual cotton bud and isoproynol trick.

[dr_mat 0]

Is the inlet air temp monitoring done on the MAF too, btw?

I know it is in later ones, but not sure..

[dr_mat 0]

Short experiment outside: started the VR, running fine.

 

Unplug MAF: no noticeable difference ...

Hit throttle - engine bogs down, splutters, and then revs.. this is repeatable four, five times, consistently repeatable. The car has never done this before!

 

Plug MAF back in: engine revs drop VERY slightly (engine is still on warm-up cycle anyway)

Now hit throttle - engine revs cleanly every time you press the throttle.

 

So - is the MAF working or not?

[dinkus 10]

Sounds like it probably is working then.

[paddyg 0]

funny...

I had that exact problem last week in the car im driving at the moment...its a Toyota Carina2 :oops: :oops: :oops:.

Anyway, had that problem, i thought it may have been blocked or partially blocked fuel filter. But I was told that because the the amount of fuel pumped to the engine is always in excess of what is required, a lot is sent back to the tank, therefore only when you're at high revs and using all the required fuel will you know if the fuel filter is blocked or partially blocked.

 

So anyway, i was taking it home to our local mechanic to have a look at, and when i got out onto open road it seemed to clear itself, and i havent had any problems since. :?

So now ive put it down to dirty fuel possibly???

i do have 217k on the clock though so i reckon its not the last of my problems!!!!

[KADVR6 0]

thanks 4 all the advice guys, is vag-com a vw only thing?? or can any garage do the test?? :?

[dinkus 10]

thanks 4 all the advice guys, is vag-com a vw only thing?? or can any garage do the test?? :?

 

It's available to anyone willing to cough up a few hundred quid for it, so I should hope most garages have it. Certainly VW specialists will.

 

It's worth having a look on the VAG-COM post to see if anyone in your area has got it - http://the-corrado.net/.archive/forum/viewtopic.php?t=7209

[Kevin Bacon 5]

Few Hundred quid! A third of that mate..... probably the best £100 you can spend on a VR6

[dr_mat 0]

Yep - you can buy a basic cable for £35; the freeware VAG-COM is enough to read and erase error codes, so all you need is a laptop (or a loooooong cable..).