ISV/IAC valve

[Dox 23]

RAC guy gave a tip a few days ago for finding inlet leaks, use a gas torch unlit around seals, gaskets, breathers etc if engine revs increase you’ve found a leak.

 

Were adults and take reasonable precautions, do it out side in small bursts away from arcing plug leads etc

If in any doubt don’t do it!

[fendervg 32]

1 hour ago, Keyo said:

Pretty sure that is the code that always comes up if your reading the car without engine running - if so nowt to worry about normal always comes up.  Cant rember the code but if its the only one coming on when engine not running its ok.  If its not have you a JP aftermarket  maf fitted ? 

The code you are thinking of that always comes up with the engine not running is:

DTC "00513 - Engine Speed Sensor (G28): No Signal"

This is for the crank position sensor at the front bottom of the block, and shows up because it is obviously not getting a signal so can be ignored. It will go awat as soon as the engine is turning.

For the one above, I would check the MAF, replace with a known good one if possible as a test, check fuel pressure and also test for air leaks anywhere in the inlet - you can also get a vacuum gauge that you can plumb in with a t-piece to measure the manifold pressure.

[fendervg 32]

13 minutes ago, Dox said:

RAC guy gave a tip a few days ago for finding inlet leaks, use a gas torch unlit around seals, gaskets, breathers etc if engine revs increase you’ve found a leak.

 

Were adults and take reasonable precautions, do it out side in small bursts away from arcing plug leads etc

If in any doubt don’t do it!

No smoking!

Carb spray on likely suspects can also work.

[Crasher 3]

Check the MVB for the TB pot value. I was having problems with the idle on forum member @Hutty car and I noticed the closed value was changing each time the throttle was opened and closed so we got a new pot from Classic which fixed it and apparently the car drives better in general.

[1xshaunx1 27]

Try swapping the pcv with a bit of pipe to see if there is any improvement 🤔 

Also if it’s acting up when the oil/water is over 80 degrees c it could be MAF. But if acting up with cold engine it will be nothing to do with MAF

[Crasher 3]

On the subject of the Air Mass Meter (MAF if you must use American TLA's) I have been unable to get the early one 026 906 461. I bought one from a company in Latvia and it was useless, the car would not run. Huty on here has the last decent used one on his car I had in my stash of test parts . The later 021 906 402 is still available from the aftermarket even if the quality isn't great.

[oneohtwo 8]

Cheers all for the advice. First port of call is the PCV as that needs replacing anyway. I have sourced a replacement for an eye watering amount... to be honest I didn't really want to pay the money as it's basically profiteering, but I also didn't really find another solution and don't have too much time to devise an alternative. 

If that doesn't fix it then will start to cycle through the options above, general leaks (Although I don't have a gas torch and not sure the neighbours would be keen!) MAF, FPR, etc...

On 5/20/2022 at 11:46 AM, Crasher said:

Check the MVB for the TB pot value. 

Apologies, what's MVB? 

[Crasher 3]

Sorry, force of habit, Measured Value Block

Edited May 24, 2022 by Crasher

[oneohtwo 8]

Ta, will have to get VCDS out again and have a look. I take it by TB pot, you are referring to potentiometer?

The new development, is that the issue seems to have become slightly intermittent. Drove it twice over the weekend and the problem didn't seem to be there. But then it returned this morning, after it had idled fine for a minute or two. 

[Crasher 3]

Yes, the target value is 9...19∠° and I aim for the middle. When set, repeated opening and closing must see it return the the same value.

Edited May 30, 2022 by Crasher

[oneohtwo 8]

Ah that's really helpful thanks. I ran the test and the throttle angle was reading 14.1∠°  And when I revved and came off the throttle it went back to 14.1 and stayed there so I guess it means that's all fine from the pot side of things?

Haven't had a chance to switch the PCV out yet to rule that out.

 

 

[oneohtwo 8]

Just to update this, I finally managed to switch the PCV valve for the new one and that appears to have fixed the problem. Idles OK and fault codes gone from VCDS (well apart from an ABS fault that has now appeared... it never stops! 😂)

[ABV-VR6 12]

That's fantastic! Good for you and thanks for the follow up. Cheers 

[Keyo 47]

27 minutes ago, oneohtwo said:

Just to update this, I finally managed to switch the PCV valve for the new one and that appears to have fixed the problem. Idles OK and fault codes gone from VCDS (well apart from an ABS fault that has now appeared... it never stops! 😂)

Congrats where did you get the pic valve have they been re made ? 👍

Edited June 5, 2022 by Keyo

[oneohtwo 8]

16 minutes ago, Keyo said:

Congrats where did you get the pic valve have they been re made ? 👍

Don't think they have been remade unfortunately, but found a guy in Germany selling a few on ebay:

VW Golf 3 VR6 2.8/2.9 Corrado Sharan Crankcase Vent Valve 021129101A | eBay

Must have got hold of the last old stock and is flogging them for outrageous prices. Looks like they've put them up again from when I bought them. It is frustrating as we need these parts and it's just profiteering, but what can you do? I checked the item against the one I had and it's a genuine AF part, got the AF stamp and part number matches, so it is at least a genuine part.

I also adjusted the dashpot. I don't think it was out particularly, but I set it up as per the Bentley manual anyway. I think it gets stuck occasionally as when I first pulled the throttle cable, the cam didn't move - so that could be the cause of the stalling at overrun issue. Hopefully readjusting it and fiddling with it might cure it for a bit as it's another NLA part I understand. I wonder if you can take it off and recondition it?

 

[1xshaunx1 27]

Holy cow that’s some Mark up £170 + postage

[ABV-VR6 12]

10 hours ago, 1xshaunx1 said:

Holy cow that’s some Mark up £170 + postage

I agree, that's an insane asking price! 

[oneohtwo 8]

On 6/6/2022 at 10:07 AM, 1xshaunx1 said:

Holy cow that’s some Mark up £170 + postage

And then some!

Something still isn't quite right with the engine, and I am a bit stumped. Still idles OK but when, after first starting from cold, I move off the revs go nuts. I'll rev it a bit, bring the clutch in, and then the revs will drop suddenly, then come back up to where they were but then continue to bounce around, from basically 0-1000 rpm. If I come off the power they continue to do so and will either stall or eventually settle down. However, this only seems to happen on the first start. If I let it run a bit, or then turn off and on again everything seems fine.

Scanned with VCDS and no fault codes, and as I had already started it from cold couldn't replicate the issue to try reading the MVBs. Throttle pot angle reading seems pretty solid and doesn't move when I hold it open, so not really sure what's going on. Bit frustrating. 

 

 

[oneohtwo 8]

One thing I have just noticed is that the RPMs on the measured blocks on VCDS don't match the tach in the instrument panel. I don't imagine the tach in the instrument panel is that accurate, but they were significantly different:

VCDS        Tach

800             ~600    (idle)

1160          ~1000

1600           ~1500

2080           ~2000

Then came off the throttle and idled again and had the following:

720/680      ~500

VCDS was constantly flicking between 720/680. Could this mean there is a faulty sensor somewhere so the ecu is not getting an accurate engine speed, or would this be a normal tolerance?  It does converge as the revs increase, which is where everything is smoother but I have noticed it sometimes will be quite jerky at low speeds low revs in 2st or 2nd gear.

The revs issue also only occurs on the initial cold start where the idle is higher. Once the idle has settled down to ~600 it seems to run fine. I pulled away straight away and was basically bouncing down the road!

 

Edited June 14, 2022 by oneohtwo

[oneohtwo 8]

If anyone is still following this saga it may have resolved itself... All a bit odd. Will keep monitoring it. I did find the throttle cable was a bit slack, and I have always thought the pedal was a bit unresponsive, so I tightened that up. Surprisingly easy job, there's just a clip that holds the cable in place, don't even need any tools.

That's improved things markedly and made low speed running a lot better, just picks up straight away now. So that could have been part of the issue. I also think the rest of the odd running at low speed is down to the dashpot being knackered. At low throttle it hardly offers any damping and is slow to react, so the throttle is just snapping shut. 

 

Edited June 19, 2022 by oneohtwo

[Cressa 44]

9 hours ago, oneohtwo said:

If anyone is still following this saga it may have resolved itself... All a bit odd. Will keep monitoring it. I did find the throttle cable was a bit slack, and I have always thought the pedal was a bit unresponsive, so I tightened that up. Surprisingly easy job, there's just a clip that holds the cable in place, don't even need any tools.

That's improved things markedly and made low speed running a lot better, just picks up straight away now. So that could have been part of the issue. I also think the rest of the odd running at low speed is down to the dashpot being knackered. At low throttle it hardly offers any damping and is slow to react, so the throttle is just snapping shut. 

 

I'm still having a good read even though I can't offer any solutions. Keep trying as we eventually get things solved.  

Then we feel good..til the next thing happens 

[ABV-VR6 12]

Ya, I'm still reading! I'm discouraged for you and applaud your tenacity. Hopefully this is it! Cheers 

[oneohtwo 8]

Oh you're absolutely right. Felt good to sort the throttle cable, felt so much better I am quite excited to drive it again.

Recommend everyone doing this, it's such an easy 5 min job to fairly transform the car.

[fendervg 32]

Probably the cable got slack over the years, or stretched a bit. Nice easy result.

The dashpot is actually an Audi part - almost impossible to get hold of, NLA and only ever seems to come up as part of a breaker's throttle body - it's also OBD1 specific.

https://www.ecstuning.com/b-genuine-volkswagen-audi-parts/dashpot/034133283/

I remember spending a long time scouring the interwebs looking for one a few years back.

[oneohtwo 8]

Did you ever have any luck finding a replacement?