ISV problem - Now just a stalling in general problem!

[Kevin Bacon 5]

Filter - It's too far away from the MAF to cause oil fouling. It's the 57i type filters that can cause that, and only when they are over oiled. If in doubt, stick to the stock filter.

 

Popping - Ignore it. It's the overrun map kicking in and the lambda and Bosch injectors are a bit slow to react.

 

This problem is caused by the MAF sensor 8 times in 10.

 

It may 'appear' to be working, but OBD1 has a canny knack of ignoring it and not telling you. The hotwire MAFs are notorious for being difficult to diagnose, even on an oscilliscope. Best bet is to replace it. £150 exchange from a Bosch dealer, or the usual bend over and take a large bill up the jacksie from VW.

 

I have no idle valve and no MAF on mine running a standalone and it's never stalled once in 5000 miles. Less is definitely more ;-)

[Jim 1]

This sounds like exactly what I had with my bad ISV. I could start the car, run it, let it idle, rev it and so on for 10-15 minutes but as soon as I started to drive it, i'd dip the clutch and it'd cut out. I used to get straight on cutting out or idle that just bounced up and down all the time. Tried cleaning the ISV many times to no effect.. replacing the ISV cured the problem flat out. Has never acted up with idle since.

 

ISV's can just go bad - and no amount of cleaning them can bring them back!

[mic_VR 3]

Jim I must admit the first time it happened I thought it was definitely the ISV, but having cleaned it and checked it all seems to be working correctly on that front.

 

cheesewire so you don't think the filter could be an issue? I was very surprised at how well it ran last night after simply cleaning out the MAF with contact cleaner, literally it seems to be completely cured. It was a good long run, fairly spirited in places, and it didn't miss a beat.

Although if it does come back I might have to quote you to my girlfriend as a good arguement for going down the turbo'd/stand alone route! :lol: :lol:

[Kevin Bacon 5]

Jim, yeah valver ISVs are bad for that. On my valver I used to have to get out and give the ISV some blunt force trauma every time the engine wouldn't start, and it would then fire and run perfectly.

 

The VR6 ISV, although subjected to immense heat, is a lot more reliable and yep, you're right, having to repeatedly clean it and lube it is a sign it's dying. A simple test would be to connect two fly leads to the ISV, then connect one lead to battery + and then pulse the negative lead on and off repeatedly. If it jams during this test, even once in say, 20 pulses, it's knackered.

 

Mic, VR6s have a strange habit of lulling you into a false sense of security with 'apparent' fixes, but it's nice whilst it lasts :lol: I went through all this myself when mine was standard and in the end, only a new MAF cured it. I replaced every other sensor and the coilpack and the fuel pump needlessly, stupid car!

 

Your filter is highly unlikely to be the problem unless you went mad with the oiling. Are there traces of filter oil in the airbox lid, especially around the MAF mounting area or in the MAF tube itself?

 

Yeah just tell your girlfriend you need a "selection of parts" to fix the idle problem, but it will be faster aswell as a side effect :lol:

[mic_VR 3]

Yeah just tell your girlfriend you need a

"selection of parts" to fix the idle problem, but it will be faster

aswell as a side effect :lol:

 

It's ok, I'll just drive sedately when she's in it! She's more likely to ask what the whooshing noise is :lol: :lol:

 

Having had a look at the airbox lid it looks pretty clean so as you say that's obviously not the issue, and I haven't oiled it yet as its only done about 2000 miles since new on the car. Guess it's back to just a waiting game now to see if it starts all over and in the meantime saving up for that 'selection of parts'

[CrazyDave 0]

Might just be the initial oil from the filter that contaminated the MAF element (especially as it's just been fitted).

 

The later 'thick film' MAF's are much better than the old wire type, but still need a clean from time to time. I always used to run a paper element but changed it along with the engine oil (every 6000 miles). Only ever had the car stall twice and after cleaning the MAF it was fine again.

 

Interesting what Kev was saying though, my car doesn't use an ISV for idle control anymore (I have one fitted but it's just for cold starting and warmup, then it's switched off). The TB is just cracked open for idle air, and it doesn't even try to stall.

[gg7aph 0]

Mine VR6 has just started doing this. I'm pondering whether to get it fully serviced and get the fuel filter changed as I reckon it's still the original judging from the service history. Is getting the ISV out and cleaning it a simple job? Probably worth doing that too.....

[mic_VR 3]

Getting the ISV off is easy, and it's straight forward to clean. Just be careful when removing the piping as it's easy to break the damper box.

 

Oh and make sure you've got some new hose clips handy as if the originals are on there you'll have to break those off.

[gg7aph 0]

Okay,

so I removed my ISV and cleaned it. It looked pretty dirty. The damper pot still has some foam left in it. I decided to leave that in there instead of trying to break it up and get it out.

 

Once all back together I started her up and got a bit of a splutter which i put down to the carb cleaner and/or WD40 working its way through the system. That sorted itself out after 5 mins and I took her out......stalled. It was also hunting slightly more than I noticed before hand and now (call me paranoid) but I can hear my fuel pump whirring away in the boot, something I've never noticed before. It's not a one off as it's stalled another 3 times since.

 

So today I unplugged the ISV and guess what? It's fine, in fact more than fine - she feels great. I've only had the car about 2 months but used to think the base idle was slightly too low - it never hunted, but often felt like it was too low while sitting in traffic or at lights. The car would sometimes shudder just ever so slightly every few seconds. Since I unplugged it it is idling about 100 or 150 rpm higher and as a result feels more confident at idle and on initial pull away. I can still hear the fuel pump whirring away though.

 

Can anyone suggest that is going on here? Is my ISV just a knacker job? It seems like it was sticking in the open position (and too much air was getting in) but as it's a spring loaded unit I doubt that. Is it safe to drive around with my ISV unplugged? will it impact my fuel economy? why is my fuel pump whirring so loudly?

[CrazyDave 0]

Sounds like the throttle body might be passing air, it should be fully shut and letting the ISV do all the work. If its cracked open the ISV will try to compensate and also if it open too much the ecu will not be registering that it's supposed to be doing idle control (cos it thinks the throttles opening).

 

If you have access to vag-com then you can check the throttle pot feedback (should be about 6 degrees but less than 12 will be fine). The throttle stop screw should have yellow sealant on it, if not it's been messed with. If no vag-com just adjust the throttle until its fully closed (you can feel it if you slacken the screw right off and then tighten it until it just touches).

 

You should then be able to plug the ISV back in to do it's job. Presume you've cleaned the MAF already?

[gg7aph 0]

Not cleaned the MAF as I can't find anything on the forums related to where it is. I presume it stands for 'Mass Airflow' sensor or something to that effect? Where is it? What does it do? How does it work?

 

As mentioned before she SEEMS to run fine with the ISV unplugged once warmed up. It hunts a little for the first few minutes when cold - but this makes sense as the ISV is a form of auto-choke, limiting air intake and keeping fuel levels higher in the mixture when cold, right?

Is this a bad idea to be driving around with it unplugged?

 

Thanks

[CrazyDave 0]

Standing in front of the car the air box is on the left. A round hose coming out of the far end and going round the back of the engine to the throttle body has a straight round tube 3" in diameter with a plug on it. That's the MAF (mass airflow meter).

 

 

Should be lots of threads around about cleaning, essentially involves carefully cleaning it with some electrical contact spray to get rid of any buildup of muck thats got past the air filter (usually problems start after fitting a K&N or similar oil impregnated element).

 

I don't think you'll do any harm without the ISV, but it'll never be as good without. It allows more air to enter when cold starting to go with the extra fuel and also raises the idle speed slightly upon initial starting, so you might find cold starting more difficult when the weather gets colder. The idle speed is also controlled using ignition advance, the ecu advances and retards the ignition to maintain the correct idle speed.

 

Sounds to me like you have at least two problems, because the ecu does a pretty good job with most situations, but if the ISV, MAF and throttle are all out of spec it'll struggle to cope.

 

I'd suggest having a look at the MAF, two different types exist, the early one has a wire, the later is what looks like a thick circuit board. The MAF has a self cleaning process that it does before starting. It heats the element to several hundred degrees to burn off any contamination, but this doesn't always work, so a good clean is worthwhile. If it is dirty it won't read at the low end of the airflow range (around idle, part throttle etc). It's a critical measuring device for the engine to know how much fuel to inject. Make sure the throttle body is adjusted correctly and that the ISV is clean.

[gg7aph 0]

I had some starting problems with my ISV unplugged so decided to clean the MAF and replug the ISV back in as recommended. Mine's a later model, with the PCB style MAF, housed in the plastic tube that comes out the back of the airbox. All I could do was spray it with some contact cleaner and shake it about a bit.

After re-fitting I experienced a bit of hunting, but after a few restarts and a run that cleared. It now seems to be fine - starting from cold this morning with no problem and not stalling at all.

My only concern is that tick-over idle seems a little lower than it was previously. Not dangerously low - like it's going to stall, just a little too low for my liking. Should I consider adjusting this? If so how? Simply through the idle adjustment screw on the throttle body? Will the ECU not just compensate for this? Where is the idle adjust screw?

 

I'm hesitant to do this as I've experienced a nightmare before when i did this on a Honda I owned. Then the ECU went crazy and made my hunting problem worse. I need a service soon so perhaps should get the professionals to do it. Can it be done via the ECU through VAGCOM?

[mic_VR 3]

When you say idles low, how low? VR's are meant to idle at about 650-700rpm, which does seem low when compared to most cars but I'd say if it isn't hunting or stalling then leave well alone. And I wouldn't touch any of the idle screws as it's the ecu that controls the idle and you may and up having more problems.

 

Have done pretty much what you've done (ie.. cleaning the MAF, ISV and checked the damper pot etc) my VR is running a million times better. So good infact that yesterday on a trip from cambridge to lakeside ikea and back, about 180miles @ 75mph, I managed to average 34.5mpg! :D

[gg7aph 0]

Thanks for the feedback - as i said i was hesitant to start tampering with Idle settings as I know how finely balanced that whole set up is. Once you get something out of whack the ECU does funny things to try to rectify it.

 

It does idle around 650-700rpm, so perhaps it's right on the money. Today though, I experienced hestitation under acceleration once it warmed up. Then, just to be a pain, after I stopped and restarted it was completely cured.

 

Time to take her to the professionals me thinks.

 

Thanks

[gg7aph 0]

Okay,

So she's back from PitStop Motorsports. She's had a new set of HT leads, plugs, air, oil and fuel filter....yet still the tickover seems too low and is very hesitant when pulling away.

While sitting at lights it will hunt - sometimes getting so low my ignition light will come on but the car will cough back into life. Even when tickover is being relatively 'steady' it's still so low as to produce an uncomfortable vibration throughout the car. At it's worst I put my foot an inch or two down on the gas and raise the clutch to pull away.....no response from the throttle so the car stutters as if to stall....then a sudden boost of fuel and a loud roar from the rear before i shoot off like a scolded kangaroo.

 

Any clues?

[mic_VR 3]

I think it's going to be your MAF thats playing up. ISV problems will usually present themselves from a cold start or if you're pulling up to stop and put your foot on the clutch.

 

I was always told that hunting was more a sign of MAF problems, although hopefully someone will be able to confirm this?

 

Can't remember whether you said you'd already changed the blue temp sender? If this has gone the ecu won't be able to recognise when the engine is hot/cold and adjust fueling accordingly, ie.. the ecu could be over-fueling at idle when warm.

[gg7aph 0]

Not Changed the blue sensor - is this the lamda?

Can you explain what it does?

[mic_VR 3]

blue temp sensor sits in the thermostat housing and is the feed to the ecu on water temp.

 

the ecu uses this to judge fueling for cold/warm/hot running temps. Common fault on them across the vw range is for them to fail and ecu thinks the car is always cold, not a problem until you're up to normal running temp and then the ecu is still trying to pump in more fuel because it thinks its cold, effectively flooding the cylinders.

 

Someone with a better knowledge of ecu or engine management will not doubt be able the explain it better but basically you end up with reduced fuel economy and rubbish idle.

 

They're pretty easy to change and only about £8 from GSF so may be worth doing anyway. Hope this helps.

[gg7aph 0]

Will a duff Lambda throw out an error code? According to VAG-COM it's not showing any.

[Dutch24V 0]

Sounds like your MAF tbh. It won't throw any error codes and gives the exact same problems you're experiencing.

 

I had the same last year and after replacing all but the MAF, I bit the bullet and problem solved.

 

Dutch

[gg7aph 0]

Update:

I initially clean the MAF and ISV on the same day to cure the random stalling problem often associated with a clogged up ISV. That appears to have gone, but has been replaced by this hunting, hesitancy and poor performance. I thought perhaps I either didn't clean the MAF properly or somehow knacked it. So I took those allen bolts off that hold the actual PCB style MAF in place and took a look at it properly, cleaned it thoroughly and all the electrical contacts and put it back... at first performance was crap, and the hesitancy and kanagaroo antics were just embarrassing. After I while it cleared itself up.

 

You 'd think I would just be grateful with that but although not hesitant from take-off and idleing better it still feels completely flat way up until around 4000rpm. I get the feeling the ECU isn't getting the right data and pumping too much fuel to each cylinder and there is a bit of flooding going on causing this 'lag' and poor economy. This could be corroborated by the fact there is absolutely no difference with the MAF plugged in or unplugged and that my fuel economy is only about 20mpg.

 

Anyone else agree with me that my MAF is dead before I go out and buy a new one?

[gg7aph 0]

Wow! I'm overwhelmed with responses! Thanks guys! :lol:

 

Anyway - it's fixed (sort of, but more of that later). A new MAF sensor and she goes like the clappers once more. Just for your info it was an exchange program - so my new MAF only cost 70 quid.

 

Next problem isn't really for this thread but I don't know if it's related or not. Basically my battery began to die. I think this was just because it was a sealed unit and so i was unable to top up the ionised water and it eventually got so low it became useless. So another 45 quid on a new battery and it started healthier than i've known it too.

 

That was about 4hours ago and it's sat on the drive patiently waiting to go out until all of a sudden it started raining (may or may not be related) and the damn alarm went off for no reason. I went out, turned it off and jumped in to start her just to be sure. No Problems - so came back inside. Within 2 mins the alarm was wailing again! Turned it off.....same thing!

I noticed that as I shut the door the hazards flash - that's shut, not lock, just shut (obviously activating the switch in the door hinge area). Also, while running it would randomly flash the hazards.

 

I decided to leave it unlocked and stood there watching it. Instead of screaming, this time it just started flashing the hazards.

 

I have a factory fit Logic 900 Alarm and Immobiliser.....anyone got any clues?

[tiddles16 0]

Dont suppose anyone has a pic of the ISV and more instructions on how to remove, clean and re-fit???

 

For the non-mechanically minded like me!!!

 

Cheers.

[Kevin Bacon 5]

Wow! I'm overwhelmed with responses! Thanks guys! :lol:

 

Anyway - it's fixed (sort of, but more of that later). A new MAF sensor and she goes like the clappers once more.

 

Well that's what we told you it was! How many more 2nd, 3rd and 4th opinions did you need?! :lol: As you're a newbie, you may not have noticed that "bad running VR6" topics like this come up very, very frequently and there is no definitive answer. If it's not the MAF, it could be any number of other thing, but 9 times out of 10 it's the MAF.

 

Just for your info it was an exchange program - so my new MAF only cost 70 quid.

 

On yours it is because you have the later 4 pin MAF. Pre 95 VR6s have a wire MAF and costs over 4 times as much as yours.

 

Next problem isn't really for this thread but I don't know if it's related or not. Basically my battery began to die. I think this was just because it was a sealed unit and so i was unable to top up the ionised water and it eventually got so low it became useless. So another 45 quid on a new battery and it started healthier than i've known it too.

 

That was about 4hours ago and it's sat on the drive patiently waiting to go out until all of a sudden it started raining (may or may not be related) and the damn alarm went off for no reason. I went out, turned it off and jumped in to start her just to be sure. No Problems - so came back inside. Within 2 mins the alarm was wailing again! Turned it off.....same thing!

I noticed that as I shut the door the hazards flash - that's shut, not lock, just shut (obviously activating the switch in the door hinge area). Also, while running it would randomly flash the hazards.

 

I decided to leave it unlocked and stood there watching it. Instead of screaming, this time it just started flashing the hazards.

 

I have a factory fit Logic 900 Alarm and Immobiliser.....anyone got any clues?

 

Bin it and fit a more reliable alarm!