Advice on lumpy, erratic 2.0 16v - being a bit crap again..

[Jim 2]

0.2v loss vs headlights going off whilst driving at night due to water corrosion.. seems like a fair loss to me!

 

Tempest has mounted his up in a nice sealed container in the wing just behind the battery - its a really good setup IMHO.

[Jim 2]

Ok! New leads came today and plumbed in three of them.. but of course lead #4 with that dreaded sensor has confounded me.

 

Worried about destroying the lead (as kerrinmay did here with his Beru leads) makes me NOT want to risk doing the same thing. I just tried dismantling one of the old leads I took off and just pulled it apart in such a way that it would not go back together again.. so any thoughts?

 

Took it out for a spin and its immediately so much better. Idle dipped down once or twice but then picked up and settled where it should be.. no bouncing, no lumpiness. Tomorrow morning will be more of a test though as thats when its worse.

 

So - any thoughts on this lead #4 and that infernal sensor? Would like to get it all done if possible!

 

Thanks.

[Phil K 0]

Someone was saying that you can run with out the infernal sensor but I wouldn't bank on it - could be worth a try though... failing that give Tim a buzz at the Phirm or Vince as I'm sure they'll be able to talk you through how to do it...

 

Good news about the improvement though :D

[Jim 2]

Well i'm booked in to visit Vince next Wednesday so could hang on till then and just get him to do it ;)

 

Just really bugging me! Clearly the leads have been replaced at some point in its life and HT lead manufacturers MUST be aware of this sensor arrangement - so why is it such a mysterious dark art getting the damn sensor on?! :)

[mrbeige 0]

when I got new leads from Wires4Cars in the US, I ordered ones without that pick-up, and when I took my car to see Vince, he said that I needed it as its used by the ECU for the detection of knock (in conjunction with the knock sensor). My ECU was retarding the timing without that pick-up connected, so I'd say you need it (Vince says so too!! :lol:)

[Jim 2]

Aye - well its there for a reason, ergo I do plan to put it on the lead.

 

I have run my old valver without it and it seemed ok but not this time!

[davidwort 0]

Well i'm booked in to visit Vince next Wednesday so could hang on till then and just get him to do it ;)

 

Just really bugging me! Clearly the leads have been replaced at some point in its life and HT lead manufacturers MUST be aware of this sensor arrangement - so why is it such a mysterious dark art getting the damn sensor on?! :)

 

Jim,

I think the VW OEM leads are made to take apart, ETKA even lists the cable in reels that you cut to the right length and shows detached connectors, worst comes to the worst and you may have to buy a genuine VAG No. 4 lead and ends. Perhaps it's worth trying to take your new no. 4 lead apart, providing the old one is still working OK. If it breaks and won't go back together then perhaps you could buy just the dizzy cap end connector from VAG and try that on your new lead, if that won't fit then resort to the rest of that lead and plug connector from VAG???

 

David.

[Jim 2]

I thought the Beru leads I bought were basically OEM's though?

[davidwort 0]

I thought the Beru leads I bought were basically OEM's though?

 

Mine are BREMI, bought as OEM from GSF years back, very good quality and OEM plug connectors as far as I can tell, but whether they are totally identical to the parts that VAG would supply I don't know.

[Jim 2]

Hm.. BREMI's were what were on the car so quite possibly originals! Couldn't see a way to take those apart though as I said earlier without making it a one way process! :(

[davidwort 0]

Hm.. BREMI's were what were on the car so quite possibly originals! Couldn't see a way to take those apart though as I said earlier without making it a one way process! :(

 

which bit gets broken? - as it's just the dizzy end that you need, it may be that any old detachable HT lead end would do the job providing the end of the lead is left OK for connecting in this way. Do you wan't to disect one of the old ones e.g. No.1 and post some pics up?

[Jim 2]

Well I took one of the old leads and basically I pulled like hell on the end cap and it finally popped out.. but the rubber around the cap was so snugly onto the plastic, it really didn't want to let go.

 

The cable was protruding and was wrapped in cloth like insulation - it just didn't look like the sort of connection that would go back in any sort of reliable / secure way.

 

Anyway - driving home tonight the car was much better. Still the occasional dip / bounce in revs (grr) but literally only happened once or twice and never threatened to cut out. I've got a slightly more youthful ISV on the way (eBay bargain) so looking forward to slapping that on as well - and if that doesnt sort it then its time for your dads suggestion of a fine tooth comb check of all plastics to look for air leaks!

 

But for now - hugely improved.

[Jim 2]

Still not fixed.

 

Its the strangest thing. I can sit in traffic and the revs will drop to where they are supposed to be and it will idle perfectly. I'll drive forward 40 yards and it'll start bouncing, virtually cutting out, etc - rev it a bit, drive forwards again, and its fine again! Its just so on / off I really cannot explain it! :(

 

Hoping its the ISV sticking or something - hope my new one gets here promptly.

[Phil K 0]

I know I sound like a broken record but I still think it's the metering unit mate...

[Jim 2]

Hm - well we inspected the metering head when having a poke around the engine bay over at davidworts dads house - we checked to see how the plate piston thingy behaved and they were satisfied that it was smooth movement with no sticking or anything like that..

[Phil K 0]

Fair enough mate - although 4 of the 5 bad units I've had have looked seemingly alright even when buggered... I guess ISV is the next logical thing to look at though! :?

[Jim 2]

I have been keeping an eye out for metering heads on eBay in case one comes up on the cheap - just worried about potential costs of rebuilding / adjusting it and trying the cheaper quicker stuff first!

[corradophil 3]

Can't remember if it has been mentioned, but have you checked the microswitch on the throttle body is working and correctly positioned? If it isn't the ECU does not know the car is at idle.

 

First easy check is to pop the bonnet and just open the throttle slightly - around 1mm off it's stops. You should be able to hear the switch click.

 

It's well worth removing the throttle body and checking the switch functions with a metre, and also setting the switch position so it operates at the correct point.

[Jim 2]

Will check that one tomorrow morning mate! :)

[Phil K 0]

I have a spare one of them (if I can find it) if you need it mate - they're £70 new :shock:

 

EDIT: Sorry mate I just remembered that I sold it a few months ago... :(

[Tempest 0]

The fairly conclusive test done on these venturi-disk driven K-Jet metering units is to with the fuel system still pressurised lift the disk from beneath with your finger, all the way to the top, whereby with a good unit you will notice a uniform resistance along the entire path, and no hard or sticking points, then let go of the disk, and it should fall back immediately. This then should indicate a freely moving piston in the metering unit itself, in which case the thing is OK, as the centre piston is the most likely cause for failure of these units (they simply can rust :shock:).

 

Still believe it to be a vac-leak or ISV related issue.

 

Tempest

[corradophil 3]

Still believe it to be a vac-leak or ISV related issue.

 

The ISV operates in an idle situation, which may not be happening if the switch is not working/working correctly. It's so easy to check, that it needs to be done, even if it just eliminates one more thing that could be causing problems.

[Jim 2]

Still haven't looked! I go to work in the dark, I leave work in the dark already! Brilliant! It'll be the first thing I check on Saturday morning before doing anything else.

 

The switch sounds very likely. The problems persist and its just bewildering. If it is a switch sticking (like the one you describe) it would certainly match the behaviour. Drive along for a minute or two - stop and it idles fine. Drive a bit more and revs stick open a little then drop rapidly, and cue bouncing idle / almost cutting out. Drive a bit more (now really lumpy) and then it might be ok.

 

Then after about 10/15 mins of mixed driving, idle suddenly decides from now on its going to be about 1,100RPM and be really hesistent to drop revs, and stick the throttle open. Only way to clear is stop and restart the car.

 

All the problems occur when the car SHOULD be idling.

[Jim 2]

Ok - managed to get lead #4 on.

 

The boot pulls up and then you can unscrew the end piece. Problem is the crimped cable over the end is oh so slightly wide for the ignition reference sensor. Spectacular design really. After about 25 minutes of squeezing the crimp a little tighter, putting a little washing up liquid around the end to make it easier, lots of pulling and lots of swearing it finally went through and I reassembled it!

 

Makes not a shred of difference. If anything its a little worse (cut out about 3 or 4 times just going round the block) :|

 

I just don't understand it. I can start it and it will sit there idling perfectly for 1 minute, 2 minutes. I start to drive, dip the clutch and bleurgh - it cuts out.

 

One thing worth mentioning - could overfuelling cause problems like this? Even sitting at idle, it does niff of fuel a little bit but more like fumes as a pose to a proper fuel leak (i've had that before and know how badly it smells of petrol)...

 

Or underfuelling?

 

Still waiting on this chuffing ISV. I hate eBay sometimes.

 

Oh - and Phil - I did check for that switch. I couldn't actually SEE a switch (does it live inside the throttle body or something?) but when moving the throttle switch away from rest about 1 or 2mm you could hear a little click come from the switch, and the same when putting it back again... so that would seem to indicate that is working as it should?

[corradophil 3]

Jim, The switch is mounted on the underneath of the throttle body and is protected by a heat shield which attaches with a couple of screws, if you want to have a look at the switch iteself the throttle body needs to be removed.

 

You can see the plug for it mounted to the front face of the throttle body.

 

The clicking you mention sounds correct, so at least it is doing something, the next step is to get a metre on it and make sure it is opperating correctly, i.e. not staying in one setting - open or closed circuit. At idle it should be closed circuit and allow current to pass through it, just off idle after it has clicked, it should be open circuit.