Occasional rough idle/stall on cold start - camshaft sensor?

[negev]

I have a 2005 B5.5 passat with the 130 PD engine.

If the car is cold and I start it and immediately drive a very short distance (i.e. pulling out into a queue of traffic), then put the clutch it, it will often start hunting (rev needle going down and hearing a bag every couple of seconds) and sometimes it will even stall. When it stalls, on restart it runs fine with no more issues.

If I let it warm up for a minute before driving it's fine. If it starts hunting and I hold it above 1000rpm for a few seconds then it's also fine. Once it's been running for a few minutes it runs fine and never skips a beat.

What could be causing this? I can't believe it's a vacuum leak because it would be more consistently problematic, same for a general timing issue. Could it be an ageing injection pump or possibly a camshaft sensor going bad without throwing a code?

[smithy602179]

Try removing the vacuum pipe to the egr and plug the vacuum pipe and try it . I had similar problem and left egr disconnected

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[negev]

Try removing the vacuum pipe to the egr and plug the vacuum pipe and try it . I had similar problem and left egr disconnected

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My EGR was replaced fairly recently, including the thing pipe that runs to it, so I don't think it's going to be the EGR.

[smithy602179]

My egr was new too but I found mine would stall too till I disconnected the pipe . It don't cost owt to try

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[negev]

Fair point, where is the pipe? Do I need to removing anything to get to it? Sorry I'm a total noob with anything under the bonnet..

[smithy602179]

Pipe is on top of engine left side as u look at engine. round silver thing pull pipe off and put a bolt in the end of the rubber pipe .

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[Rob69]

With that age engine it could be injector wiring harness, MAF sensor, tandem pump or air in fuel, clearing the air after a few mins running. A scan would be good starting point and thorough check of all fuel and vacuum hoses, could be egr related but i tend to think air getting in fuel or in tank fuel pump not supplying the tandem pump and tandem pump being starved on start up after the engine has stood for a while.

[negev]

With that age engine it could be injector wiring harness, MAF sensor, tandem pump or air in fuel, clearing the air after a few mins running. A scan would be good starting point and thorough check of all fuel and vacuum hoses, could be egr related but i tend to think air getting in fuel or in tank fuel pump not supplying the tandem pump and tandem pump being starved on start up after the engine has stood for a while.

Thanks, is the tandem pump the same as the vacuum pump? If so it was replaced recently so should be good. I've had this issue for months, scanned it many times but no codes. So possibly loom, maf or fuel pump.. is there a way to narrow it down without spending lots of money on guesses?

Also odd is that it seems to be worse if I've got the steering on full lock when the clutch goes in, I guess because the pump is working sapping power from the engine? When it runs rough its like a cycle, bangs every couple of seconds like the timing is thrown out.

If I just work around it will the occasional bang cause any damage? I guess its probably a misfire but I thought a misfire would throw codes and a CEL.

[smithy602179]

Wat was the solution to all your woes

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[negev]

Wat was the solution to all your woes

I took it in recently and the first thing they found was that the top pipe had snapped off the EGR valve (!!). It was only replaced a couple of months ago so I took it back to where it was fitted and they replaced it under warranty. Issue still persists though so now it's booked in again for Monday. :(

[smithy602179]

Good luck with it. Least they changed the egr for free

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[negev]

So finally the garage looked at it, they said with a scanner they can see two injectors showing bad readings on startup which suggests one or both is faulty, so they want to send them away for diagnosis and possibly reconditioning. Bit scary as we're meant to be going on holiday in a couple of weeks and need the car to drive across france!

Is it plausible that it could just be the wiring loom? It has no error codes and only misbehaves a little bit on startup when it's cold, once it's been running for a few minutes it's ok. I'm planning to ask them to change the loom now as I need the car to pick up my wife from the airport on saturday, then if it's still doing it I'll give it back on monday and pray that they can get the injectors done in time for our holiday. They reckon it's enough time but it's still cutting it too close for comfort!

[negev]

loom replaced today but still missing :/ tempted to leave it until after my holiday as it runs fine once it's warm. it's been like this since january so should be ok for a few more weeks. fingers crossed!

[negev]

well this is interesting! yesterday they told me that although it was better there was still a slight misfire when it was cold. this morning they dropped it off and the driver said that it was absolutely fine, and that he'd driven it when it had the problem but this morning it drove perfectly and didn't miss a beat. i called the service dept to ask about the discrepancy and they said "if you rev it to 5000 when it's cold and then let it fall there's a slight shudder which is a misfire".. but that sounds like a really bad thing to even try! nobody should be revving a cold car to 5000rpm. before it went in i only needed to rev it to just over 1000 to make it start misfiring so if that doesn't happen any more and it doesn't misfire when cold and moving slowly like it used to then i'm going to just assume it's fixed.

revving a cold engine to 5000rpm seems like asking for trouble!

[negev]

so the next day i discovered the problem was still there with the new loom, misfiring from cold just as bad as before. took it to a diesel specialist over the weekend and today they told me that all four injectors are past their service life and need replacing.

bit expensive at £600+vat but the car is otherwise in very good condition, no wear on the cam lobes at all at 140k - the specialist were even asking me if i'd replaced it!

[negev]

Ok so to complete the story, total of £1132 for new injectors and an oil change, and then once they'd done all that the mechanic noticed the alternator clutch pulley was siezed so now another £550+vat for a new alternator, clutch pulley, belt etc.

They could send the alternator away for repair instead of replacing it which would be slightly cheaper but it'd take too long as we're going on holiday end of next week :( I thought a B5 would be reliable and not need huge amounts of maintenance but it's only been 7 months and it already owes me thousands!

[smithy602179]

Welcome to the joys of owning a b5 .

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[smithy602179]

On a serious note tho
Darkside Developments - Alternator Clutch Pulley for 1.9 & 2.0 TDi Models - 5 Groove (http://www.darksidedevelopments.co.uk/products/alternator-clutch-pulley-for-1-9-2-0-tdi-models-5-groove.html)

It doesn't cost that much to do timing and water pump at vw themselves
£479 all In


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