Running with MAF disconnected!......updated 28/03/2005

[edd 0]

Right sorry i know a pretty well covered topic but i got no immediate satisfaction/stress relief from the search so:

 

Gutted cos im scared of the future of this path laid before me - having watched the forum long enough i have been dreading this day.

 

"Vr's on a stall-a-thon."

 

Probably stalled 15 times + on the way to work this morn. Happens pulling up to junctions. Feels like revs dying too quick and ISV not coping. Gave ISV a good clean yesterday alls fine there and throttle damper thingy seems okay.

 

Dieing is very erratic seems to be no similarities between events. But it has been getting progressivley worse. Also get some erratic hunting at idle whereby the hunt gets greater and greater the more it seems to try and correct itself until it eventually dies.

 

Question is: I was thinking that if the MAF was to blame i could just disconnect it let it go into basic mode and see if that stopped stalling, albiet with reduced perfomance levels, but when tried the car wont run with MAF disconnected, it will run for a few seconds then die.

 

Is this right? I thought the car should run with it disconnected so as not to be stranded anywhere if it went wrong!!

 

EH

[dinkus 10]

No idea if that's the MAF or not, but it's definitely worth plugging VAG-COM in and seeing what it has to say for itself.

 

You can test to see if the MAF's completely dead though - fire it up and let it idle for a bit. Then pull the plug on the MAF.

 

If nothing happens, then the MAF's dead and you're already running without it (yes it does run without it).

 

If the engine coughs and splutters and probably stalls, then the MAF was working ok at the time you unplugged it (obviously if you have some dodgy, intermittant wiring fault then that doesn't help you any).

 

If you then restart the engine, it should run fairly ok without the MAF connected.

[edd 0]

"If you then restart the engine, it should run fairly ok without the MAF connected"

 

Yep you see this is the bit thats is confusing/worrying me as it wont run if started with MAF disconnected. But does die if disconnected whilst running.

 

Does this indicate to a problem elsewhere in (ECU etc).

 

Can't be arsed with this.

 

Mines an early double pin connector for VAG com and don't know anybody close. Will require a trip up to see Vince, which will no doubt include a few hairy no power steering moments!!

[Dutch24V 0]

My '94 coil-packed VR won't run with the MAF disconnected either. I have a new TPS and O2 sensor too.

 

This happened to me last week btw. After I replaced the MAF and TPS about a year ago she's been running just fine, with no stalling. 2 weeks ago she started stalling again (about 4-5 times on the drive home). I just disconnected the battery for 5 minutes and she's not stalled since. I think every now-and-then you need to recalibrate the TPS. The simplest way is to reset the ECU. I doidn't bother with Basic Settings either btw.

 

Dutch

[edd 0]

Cheers..........of i go to go borrow a spanner!!

[Kevin Bacon 5]

The ECU needs to see that the MAF is connected with the older style ones but doesn't concern itself with the actual output, so disconnecting will usually cause it to stall. It's all a bit grey, there are no definitive answers as some engines behave differently to others.

 

I could whip the MAF off after a cold start and the engine would keep running no problem as there's no lambda for the 1st two minutes of startup, so loads of fuel gets chucked in. When the engine was hot though, forget it. Wouldn't run without a MAF at all......except the time when the MAF utterly fried itself and was putting 12V down the signal wire (instead of 1!), so you see, it's very grey and vague.....

 

I suspect the MAF is your problem though, the ECU isn't happy with the output. See if you can borrow one to confirm.

[edd 0]

"I could whip the MAF off after a cold start and the engine would keep running no problem as there's no lambda for the 1st two minutes of startup"

 

yep thats how mines is.

 

Just done an ecu reset and taken for a spin no stalling yet and did feel noticeabley smoother. But thats a classic corrado trait they just pretend to let you think you've fixed em for a while.

 

I'll see how it goes and report back.

[.Rich. 0]

Im near newent which isn't far from malvern and have vag-com so if you get stuck we can give that a whirl. Mine's a vr6 so you could also try my maf if needs be.

 

Ive not used vag-com yet so im no expert

[dinkus 10]

.Rich. - have you got the 2x2 adapter (2, 2-pin plugs - one white and black), or just the big multi-pin jobby?

[.Rich. 0]

I certainly have the older 2x2 (1white, 1black) adapter, which plugs into a big multi-pin connector.

 

Am i right in saying this means i have both style of connectors?

[dr_mat 0]

Just to upset the apple cart (once again), if I disconnect my MAF at idle with the engine warm, the engine carries on as if nothing happened.

.. until you try to rev it, at which point it gulps at the air like a goldfish trying to fly and fails to get anywhere..

But the fundamental point here is that you cannot trust the "disconnect the MAF" test. Clearly my MAF works, because the car becomes undriveable without it, but clearly the idle program is not perturbed by it being unplugged.

 

Also it's worth noting that resetting the ECU without doing the whole basic settings procedure *can* potentially leave the ECU's adaptation way off kilter. In most cases it appears to adapt pretty quickly and get on with life, but that isn't a fix-all... Anything can happen with a self-calibration system. It could get it very very wrong. I'm sure Bosch worked very hard to make that unlikely, but it's just statistics.

[Kevin Bacon 5]

But you have a 4 pin MAF and they work differently.

 

I can also pull my OBD2 MAF and on the engine runs... it's the 6 pin wire MAFs and corresponding ECUs (AG) that don't like the connection being pulled.

 

Basic settings does nothing on OBD1. If you pull the ECU plug and reconnect, it will poll the sensors and run alright for a while, but as soon as the lambda goes open loop after the preheat, if it's still not happy with the MAF output, it will consult the substitutes and you're back to square one.

 

There is a very fine line with OBD1's sensors and ISV at idle that is hard to diagnose, it either works or it doesn't. OBD2 doesn't care... it has a motorised throttle and will flip the throttle at any angle it chooses to maintain the idle and it never, ever stalls....even if the lambda is pulled.

[dr_mat 0]

But you have a 4 pin MAF and they work differently.

 

Yep, and the original question came without a specification of which model they were referring to (as far as I could see), hence me pointing this out.. :)

[dinkus 10]

I certainly have the older 2x2 (1white, 1black) adapter, which plugs into a big multi-pin connector.

 

Am i right in saying this means i have both style of connectors?

 

Yup :)

[quicky1980 0]

doubt it will be this but on my golf 16v it had similar symptons. turned out to be a bad earth on the head. wire snapped off due to engine movements. worth a look?

[dazzyvr6 0]

just found this info not sure if it applies to uk VR6's though :? http://tinyurl.com/ggf9w

[bcstudent 0]

just found this info not sure if it applies to uk VR6's though :? http://tinyurl.com/ggf9w

 

I honestly can't see why it wouldn't. That's a good find dazzy. However UK VRs apparently, according to the rest of this thread, use two different types of MAF sensor. This info possibly only relates to one of them.

[Kevin Bacon 5]

Yeah it's for the later plastic 4 pin MAFs. Good find though!

 

I'll order a Golf MAF and see if the internals are the same as the ones we get in the UK.

[edd 0]

Well god knows but i dont hate my C so much today so im not so worried. Done 100 odd miles since the reset yesterday and shes flying and really smooth. Thanks for the offer Rich may well take you up on that when i get some time free. I work at Glos Hospital and actually bought my car from just outside Newent. We can try and fig out VAG com for ourselves.

 

I think MAF discussion will be here to stay on this forum 4 ever.

[.Rich. 0]

ok edd just pm me if you need it

[edd 0]

Bo**ocks 150miles later ive gone full circle - stalled twice on the way in to work this morning. Also sometimes has hesitancey when pulling away from junctions almost like its missing or fuel starvation- not plugs/oil related as ive had full engine rebuild in last 10000k. I have just remembered that i do get an intermittent reading on the 02 sensor on VAG com - if this has become more severe could this cause the problem?? I dont understand why the ecu reset sorts the problem but only for a short period of time.

 

The problem is there is so much to check and they all cost money!! Mines a dizzy too by the way. things that could be contributing??? hall sender, ECU, Dizzy, MAF,leads, Fuel pump any more.....do any stand out!

 

Any more ideas anyone??!

[Kevin Bacon 5]

Wait until Vince has pefected his MAF-less remap and bin the fecker 8)

 

A fault on the lambda is not a good sign though, might want to replace that.

[edd 0]

well that was next planned thing for Vince but it was previosuly so intermittent that we couldn't get it to show up unless it was driven for a fair few miles. Kept replacing O2 sensors but got the same VAG com error so it must be the wiring. if this had become more intermittant what efffect would it have?

[dr_mat 0]

The ECU reset just forces the thing to run a bit rich for a while. As soon as it adapts back down to efficient running, any weaknesses in the system will become apparent with roughness and stalling ..

The ECU reset fixes nothing.

[keithmac 0]

Some people have had success with filling the inside of the connector with dielectric grease, from what I`ve read the MAF could fail at any time, 60k to 80k seems most common?