VR6 won't idle

[jamiej 0]

Hi all,

This morning, I started my car (1997 VR6 Golf OBDII AAA) and it wouldn't hold an idle at all.

It has done this before but the problem just went away.

I drove to Sainsburys riding the brakes thinking that when the engine got a bit warmer the engine would be happier but not much luck.

The engine will hold a very low idle but the engine doesn't at all sound happy.

It runs perfectly normally, no hesitations up the rev range and have just had it MOTd puffing out perfect emission readings.

So what could this be, I am unconvinced that it's anything like a carbon build up on the throttle body or muck in the MAF as, like I said, it has been running perfectly.

One thing I can hear from the engine bay is a hissing noise when the engine cuts out, it sounds like its coming from the intake plenum ?? any ideas.

Any thoughts/opinions/suggestions very much appreciated.

Jamie

[cabrioman 6]

best thing to do is get it on vagcom mate and check for some fault codes .... and go from there buddy

[jamiej 0]

Where is the best way to get VagCom without "stealing it"

[Indian 0]

Measure the speed sensor G28 with a new one or just change it.

[DrRich 1]

The hissing noise sounds like a vacuum leak to me. If you can get it to idle at all, poke around the engine bay listening for where the hiss comes from. There are two vacuum hoses at the front which are in the intake plenum area (front right as you look from the front of the car). The small diameter one goes to the fuel pressure regulator, the larger one goes to the brake booster at the bulkhead.

I have found the rubber gets perished on the larger one where it connects the intake to the long plastic piping - worth a look. It might not be obvious that the piping is broken when it's in position - you might need to dismantle it (just hose clips) and stretch it around a bit to see any cracks. You could try wrapping each pipe with tape and see if there is any change - not a permanent solution but might reduce the leak and prove where the problem is.

A vac leak will cause all sorts of trouble at idle (the engine doesn't know about the extra air getting into the combustion chambers because it didn't get measured by the MAF), but less trouble as the rpms rise because the extra air is a smaller proportion of the total as the throttle opens. Also, there is less vacuum at higher throttle opening, so less extra air is sucked in. The oxygen (lambda) sensor can adjust for extra air to some degree, but anything larger than a small leak will be too much and show up as a fault code.

Hope you sort it soon!

[jamiej 0]

I have looked and listened to the vac pipes and nothing seems obvious.

This may seems a silly suggestion but is there a chance that this could be down to a bad battery/alternatior. After a high idle the idle would be held at about 600rpm but then any rev and and lift after would cause the revs to dip below 400 rpm and it would conk out.

Annoyingly, my multimeter is with my Dad so i cant check the output of the battery.

Arghh, this is so annoying, its been faultless (pretty much) since i bought it !

[Vw_owner 1]

hi, when i had bad ideling it was down to the MAF plug being flooded with water, the revs were up and down from 600-1800 and the battery light would come on then cut out, so this hissing noise only happens after your engine cuts out?

[jamiej 0]

Just took the car for about an hours drive.

For the first 10 minutes, I was forcing an idle by feathering the throttle, then the engine would hold its own idle but at about 2000 to 2500 RPM, then this would drop to about 1500. It was doing this for ages, literally idling wherever the revs where when I released the throttle.

There was also a delay in the throttle response coming off the power, the engine would maintain the RPM and then drop with a bit of a shudder, that you could feel.

On the last 10 miles, the idle stabilised to about 1000RPM.

Once I got the car back, I left the car running and disconnected the MAF, this had no change whatsoever-ever to running of the car and after a few blips opf the throttle, it appeared the MAF wasn't really adding anything.

Does this mean new MAF ? Do the above (new) symptoms suggest anything else ?

Jamie

[stormgreynolan 0]

have u checked and double checked for air leaks get it smoke tested if your local garage has the machine to do so

[jamiej 0]

Its hammering it down with rain at the moment so I will check next time it's dry. Does the above not point to MAF at all? Vac leak the most probable cause??

[DrRich 1]

It does still sound like a vac leak to me (the off idle hesitation as well) but the MAF could be to blame since you tested it. It might be worth giving the sensor element a spray with electrical contact cleaner (Maplin sells good stuff, think Halfords sell it too).

What I do is:

1: Take MAF off car (undo hose clips at each end and it pulls out of the pipes)

2: Spray cleaner onto the thin 'wafer' in the middle, both sides

3: Let it dry off (takes a few minutes)

4: Refit.

I'm assuming your MAF is the same as mine (since yours is a '97) - thanks to the Vortex for this pic:

I also wipe it with a cotton bud (gently!) and frequently get a lot of dirt off. Be careful if you do this - I've not broken anything yet but use your common sense!!)

Good luck!

[Gazbarber1982 3]

There isn't a lot of vacuum lines running off the manifold so try pinching the lines to see if that helps. Get it on vagcom though for a detailed fault code list or anyone with a cheap fault code reader could point you in the right direction.

[jamiej 0]

Weather permitting, I'm going to have another look tonight, I will start with the MAF and then have a look at the vac lines.

If I cannot hear anything, would anyone recommend that "brake cleaner" method or is this a little destructive ?!?. Presumably the main line is the one which runs up the Right (looking down at the engine from the front), to the brake servo. I have tried to find on the web a good diagram but to no avail.

Thanks for your ideas, i'll let you know how i get on.

[jamiej 0]

It goes on, I had a great idea of going for a drive then calling the RAC, as I cannot get my Uni copy of VAG-COM or the Freeware version of VCDS to work with my car.

waited for about an hour and then called it off.

Going to have a good prod around tonight, but in the meantime have ordered one of these

U281

It looks like a cheapy fault code reader and im sure will be much less of a headache than all my versions and copies of VAG-COM with a eBay connector.

I will let you know how i get on tonight !

Jamie

[jamiej 0]

Just had another look.

I have cleaned the MAF, it looked pretty spotless (as you would imagine) but i gave it a good dousing in Electrical Contact Cleaner but still to no avail.

I managed to get it to roughly idle and checked the lines by pinching and squeezing them but nothing made any difference.

Could one of your genii point me towards some likely culprits, pictures below. Please forgive the blue "K&N", i inherited that from its previous owner.

[jamiej 0]

I have just run a VAG-COM scan (Uni copy, with old laptop), fault codes as below

00281 - Vehicle Speed Sensor (G68)

03-10 - No Signal – Intermittent

00533 - Idle Speed Regulation

Adaptation Limit (Add) Exceeded

00522 - Engine Coolant Temp. Sensor (G62): Break in wiring / short circuit to positive

00282 - Throttle Position Actuator (V60)

Implausible Signal

00553 - Mass Air Flow Sensor (G70)

31-10 - Open or Short to Ground - Intermittent

I also got 00282 and 17978 and 01247.

So, presumably this tells me exactly what you guys are saying ?

Coincidently, I ran a check about a year ago and got the 281 533 and 282 errors, so I am thinking, its the coolant sensor. My coolant cap was cracked about a month ago and I was running with very low coolant, could this have possibly damaged to the sensor and ... caused the idle issue ??

What do you think ?

Jamie

[DrRich 1]

I would clear these codes, now you've made a note of them, and drive again for a bit - some of them could be historical so worth seeing what comes back.

A coolant sensor is cheap (around £15 from GSF/ECP) and easy to replace, so might be place to start if that codes returns.

If your copy of VAGCOM allows, it might be worth calibrating the throttle body. On mine (a '96) that's by changing to 'Basic Settings' and putting in 098 into the box. You'll hear the TB running through its range, wait about 30 secs just to be sure, then "Done, Go Back". It should say "ADP OK", anything else means a faulty TB and ££££ - hope it's not that!

If you've never cleaned the TB it's worth taking it off (4 hex bolts, 6 or 8mm - can't remember). Don't drop the gasket as you will reuse it. Then spray carb cleaner around the throttle disc and everywhere. I open the disc by twisting the throttle lever (DON'T push the disc open, it'll damage the motor) and then clean the edges of the disc too. Sometimes, it can get so dirty that the disc can't close properly due to the crud and you have an air leak past it. Here's a link for a Mk4 - the pipes etc will be different but you'll get the idea:

http://www.vaglinks.com/Docs/VW/MKIV/VW_MKIV_VR6_Throttle_Body_Cleaning_DIY.pdf

[jamiej 0]

Thanks DrRish, that is most helpful.

I will try clearing the codes, going for a spin and then re-running the scan. To make matter more annoying, the laptop I have to use (still not totally sure why) only lasts about 5 minutes when not plugged in so i need to do it all pretty swiftly !

I will also try and re-calibrate the throttle body, I am not toally sure of the allowances on my VAGCOM copy but we'll soon see.

Re:Throttle body, I will have to wait a bit until I do that as all my tools are currently not with me.

If I can drive the car, and it appears that only the idle is the real issue, would you imagine that dirving the car would do it any harm ?

[DrRich 1]

Wouldn't think there's likely to be too much problem if it drives well off idle. There's no code for the lambda sensor, which might allow dangerously lean or rich conditions (and even then only under extreme circumstances like prolonged full throttle - ie racing - which you wouldn't do on a public road now would you?)

Looking at your pictures doesn't throw up any obvious problems. Another place to look for a vacuum leak is at the PCV (Positive Crankcase Ventilation) valve - it's the pipe that comes out the back of the crankcase, has a corrugated pipe, with a plastic disc-like thing in the middle, then joins the intake elbow. These can deteriorate and crack easily as they fill with oil fumes from the crankcase and are near the hot exhaust manifold.

[jamiej 0]

Cleared the codes and went for another drive.

The only codes that are appearing now are 00282 and 00533.

I tried to reset the throttle as instructed but I do not have the permissions to do that.

One thing i noticed though was that when the car was idling high, the throttle almost seemed stuck, its was being held open and i could rock the throttle mechanism with no resistance.

All this seems to be pointing to the throttle (code 00282 is throttle position actuator), if the motor is playing up then there is a good chance that it wouldn't be able to hold an idle. It makes sense as it drives fine off the idle, but there is a slight delay when i lift off, presumably this is the throttle sticking slightly and then moving back.

Where does this lead me, I did give the throttle a little clean but it was in situ.

Any more for any more.

Would a SNAP-ON hand held diagnostics unit be able to reset the throttle actuator ??

Cheers guys

Jamie

[Vw_owner 1]

unplug the maf and spray wd40 on its electrical contacts, dont worry it wont damage anything,even if it looks dry, if theres any moisture it will displace it,

[DrRich 1]

From what you've said it really sounds as if the TB disc would benefit from a clean. OBD2 controls the idle by adjusting the position of the disc to allow a controlled amount of air past. If there's too much carbonized crud around the edge of the disc, and also around the inside of the TB passage, then that amount of air is changed; the TB will adapt to the buildup over time, constantly changing its idle stop point, but eventually it will reach a point where it can't get it right. Also, the crud doesn't get laid down in a convenient, symmetrical manner, and the TB expects airflow to increase linearly as its opening angle increases.

Unfortunately, a good clean, with the TB off (it's the only way to do anything more than a superficial job, trust me) followed by an adaptation with VAGCOM is the only way to sort this - or rule it out as the problem...

I think the SnapOn VCS module will work fine based on this document:

http://findpdf.us/d/1177242

(look for a small "Download now.." link, halfway down the page on the left side, below an advert). It also gives a useful overview of the Motronic ECU as well.

I've heard that leaving the ignition on with the door open for 20 seconds (or something like that) might force an adaptation but couldn't say for sure. The TB will adapt over time, but it's a looooong time.

Incidentally, my TB makes a motor noise, which is nearly identical to an adaptation, every time I turn the ignition on but don't start the engine (and perhaps then also but I can't hear it) - not sure what it's doing; perhaps a self test or something.

Good luck!

[jamiej 0]

What an incredibly useful post, thanks very much.

After all this, turned the key this morning and the car started on the button and ran like a dream, very very confusing. I've driven about 100 miles today, stop start cool warm and it's perfect? Very odd.

Now as I said, it has done this before but never for this long.

The throttle body almost certainly does need a clean, I have never cleaned it and I noticed that was a lot of gunk inside when I had a look whilst trying to diagnose the issue.

Maybe a managed to perform a re-calibration of the throttle by mistake.

Lesson learned though and also I would highly recommend the U281 fault code scanner!

Thanks all.

Jamie

[DrRich 1]

Well, whatever it was, the main thing is it's going well now!

I'd strongly recommend a TB clean when you have an hour or two though - it has made a huge difference to how smoothly the engine runs in my cars before now.

Congrats, and I hope it stays fixed!

[jamiej 0]

Just whipped the TB off and it was filthy. Gave it a proper clean with a toothbrush, carb cleaner, the works!

All back together and car is still running fine so hopefully that's that sorted.

Only think is that there is a slight stick cowing off the throttle, so can't be sure if that's the throttle or a vac leak, it's hardly noticeable but you can tell that something is not 100%.

Thanks again all.

Jamie