Cutting out VR

[Jonny_L 0]

Hi guys, my corrado has started stalling occasionally when slowing down for lights, junctions etc.

When i bought the car, the previous owner told me about the problem, but i can't remember what part he said needed replacing.

something like air _____ meter. so i'm thinking air flow meter, would this make the car stall if its going wrong? otherwise what else could it be.

Serves me right for not listening properly first time round!

Jonny

[dazzyvr6 0]

sounds more like the isv need cleaning or renewing

[chrishill 0]

a faulty mass air flow meter can cause stalling, but so can alot of other things, bearing in mind a new MAF is around £350 I'd check out the cheaper options first if possible! you can test the MAF with a voltmeter, although I dont remember the specifics of which wire and how many volts it should be showing, I've a feeling its 4.5v.

[dr_mat 0]

MAF voltage output should be dependant on the air flow rate (obviously).. It should peak at less than 5v on a standard VR, and that at full throttle and 6000rpm, so at idle it'll be MUCH lower.

BUT the stalling-at-juntions can be caused by so many different things that jumping in and assuming it's the MAF is not the right thing to do.

Check the search, but this has been discussed lots of times before. Usually with a different outcome ..

[chrishill 0]

just to give you a few pointers, since I've done the same searches you'll be doing before now, possiblities are (amongst others)

 

Crank position sensor

MAF

ECU relay

Fuel pump (and relay)

MAF (last resort!)

Lamba Probe

 

from what I've read the eventual result of the symptoms they produce when faulty, can sometimes be stalling.

[dr_mat 0]

Don't forget the ECU basic settings procedure .. which some cars don't seem to need, but it was done for a reason ..

[Kevin Bacon 5]

MAF voltage output should be dependant on the air flow rate (obviously).. It should peak at less than 5v on a standard VR, and that at full throttle and 6000rpm, so at idle it'll be MUCH lower.

 

Where'd you get 6000rpm from? It's proportional to air mass, not revs but the output should be around 1V at idle, which equates to an air mass 'learned value' of 9 - 10 g/s usually.

Red wire on 6pin MAFs and the blue/red wire on 4 pin jobs are your output signal wires.

 

BUT the stalling-at-juntions can be caused by so many different things that jumping in and assuming it's the MAF is not the right thing to do.

 

Chris said the MAF can cause stalling, he didn't suggest it is the problem. Please don't turn this into another Blue nothelle style "Why rebuild the engine to fix a stall?" type threads, in which particular case he was wrong anyway :roll:

 

People are sharing their experiences. It's up to the thread starter if he wants to spend £300 on a MAF or not......but I would suggest a VAG-COM scan first to outrule a faulty TPS and fuelling issues.

[Jonny_L 0]

Thanks for all the comments, it's given me a lot to try.

The only reason i think it is the MAF sensor is because i think the previous owner told me that was the problem. for him, it only stalled once, but its happened 3 times in 5 days for me now, so whatever it is, it's getting worse.

Mind you, he told me the new part is about £50-100, so its probably something different after all.

 

I have just ordered a VAG-com lead off ebay, so i'll give that a try first and see what happens.

i'll have a dig about for my multimeter and try testing the MAF in the meantime.

 

As for the VAG-com, obviously i get the software from ross-tech, hook the lead up to the car (16 pin by the gear select), and the other end to my old pc. is there anything else i need to do first? (besides learning to use the software)

Cheers, Jonny

[dr_mat 0]

MAF voltage output should be dependant on the air flow rate (obviously).. It should peak at less than 5v on a standard VR, and that at full throttle and 6000rpm, so at idle it'll be MUCH lower.

 

Where'd you get 6000rpm from? It's proportional to air mass, not revs but the output should be around 1V at idle, which equates to an air mass 'learned value' of 9 - 10 g/s usually.

Red wire on 6pin MAFs and the blue/red wire on 4 pin jobs are your output signal wires.

 

I made it all up, to prove a point. It's not *that* easy to test the MAF as you well know kev, so I didn't want anyone thinking they should expect to be able to diagnose a faulty MAF using a multimeter and seeing "some volts". Chris's comment was "I think it should be 4.5v" which is (no offence to chris) about as useful as a chocolate teapot... :)

 

My comments aren't much more helpful, (I don't have your first hand experience with faulty MAF sensors, kevHotwire ), but I think serve to explain a little more about what to expect from a MAF sensor. (Of course it's proportional to air mass, but it's going to peak at full throttle and high RPM isn't it?)

 

BUT the stalling-at-juntions can be caused by so many different things that jumping in and assuming it's the MAF is not the right thing to do.

 

Chris said the MAF can cause stalling, he didn't suggest it is the problem.

 

People are sharing their experiences. It's up to the thread starter if he wants to spend £300 on a MAF or not......

 

That paragraph wasn't aimed at Chris.. Sure, if Johnny_L wants to spend £x00 based on the word of the previous owner of his car, go for it, it's not my money. (But I think he doesn't want to do that, otherwise he wouldn't have asked the all-knowing Corrado Forum would he?)

Anyway, I would wager that the previous owner didn't know what was causing the fault either, Johnny_L, so I'd be inclined to start diagnosing from scratch IIWY.

 

NOW you see my point? Only trying to help, as usual .. Got jumped on, as usual ..

 

I always think a VAG-COM scan is a good idea ... never disagreed with anyone there...

[chrishill 0]

I didnt take it as being aimed at me, just a general observation that pointing the finger at the MAF and not looking in other areas is the wrong thing to do, which is a fair point.

 

as for my comments on testing the MAF, i 'did' say I couldnt remember the specifics, just going off how chrisvr6 nos tested mine when I thought it was faulty and hoped someone would fill in the detials of exactly how to test it and what the figures should be, which kev did in the end.

 

reguardless, hopfully Jonny_L will use the above information and get his car running right again.

 

I'll leave the VAG-COM question answering to someone else ;)

[dr_mat 0]

Re: testing MAFs - neither could I .. :)

I remembered some comments from Kev's posts about his recent adventures in OBD2 land, but not much more than that ... :)

[Jonny_L 0]

Chill, everyone! Just going from what the previous owner told me.

Anyway, i've had a prod with the multimeter, which although it might not be the best way of testing, it's proven that the voltage is about right. (according to what i've found on some other threads in search, anyway)

its a 6 pin job. at idle, i've got 2.3v, and at 3000 rpm i've got 2.8v. it increases steadily with the revs. so i assume that this means the MAF is doing something right, if not everything.

 

for the record, i definately would rather avoid having to spend £300 on it, and to be honest, i'd leave it til it stalled at every junction before i spent that much!

Especially since i've just sent off 4 speedlines to get refurbed and 4 new boots.

I can't wait to get VAG-com now, i wonder how many faults its gonna find!

[Kevin Bacon 5]

Sounds like the MAF is OK from the rudimentary testing (albeit with a slightly high voltage, but the 6 pin jobs do run a little higher than the later ones at idle), certainly nothing there that could cause a stall. MAFs can be had from a local Bosch place for £150 exchange, the dealers just wang there monstrous mark-up on top.

 

If you look behind the throttle body, you will see a little plastic piston that catches a roller on the throttle arm. You can adjust this and move it up to catch the throttle a bit earlier. Undo the 13mm nut underneath the bracket that holds the piston and you'll see what needs doing. Don't screw it too far up or you'll move the throttle off it's factory set stop. It's a trial and error thing.

 

Also clean out the idle valve (it's the Silver L shaped Bosch thing next to the the throttle) as they're prone to getting clogged with crank case gunge and jamming. Whilst you're there, there's a black plastic damper pot attached to the idle valve too. It's got plastic foam in it which can sometimes get sucked into the hose and block the air path. Check that's OK and also that the pot and associated hosing aren't split.

 

Next, clean off the crank case gunge from the throttle flap too.

 

How are your air filter, plugs, oil and HT leads? Are they recent?

 

The VR is prone to stalling, largely because the rate of air flow drops very suddenly when you back off and the idling system struggles to catch it if all the other bits and bobs aren't 100%.

 

The throttle position sensor is another favourite. It's critical and does the bulk of the fuelling. It's the only loom in the entire harness that has gold contacts end to end, it's the main man for fuelling!

 

There's a thing called 'basic settings' in VAG-COM that is apparently supposed to 'harmonise' the throttle sensor to the ECU so that it knows what position it's at. You can give that a whirl too when you get your VAG-COM sorted.

 

Check also for broken or chaffed wires around the throttle and by that big round plug above the gearbox.

 

Until you get VAG-COM, there's not much else we can suggest as we need to outrule faulty sensors with that first.

[matt_corradovr6 0]

my vr very occasionnalyy stalls at the lights. however when i had my car rolling roaded at stealth it did show an intermittent lamda probe fault. just thought i'd add to the melee!