Serious problems with stalling and idle stability

[sepulchrave]

Hi all,

Been a while since I was here last but there have been some new and ugly developments!

My car is a Fabia I 1.4 16v AUB manual.

The problems started during the very cold weather before Christmas, occasionally the car would stall after a long motorway drive when pulling off and braking at a motorway exit. The problem would disappear after a restart.

Then the stalling started to happen in traffic but would usually clear after a restart or two. Sometimes the EPC light would come on as well but would usually clear after parking up and then restarting.

Now the car is virtually unusable, it will always start from cold but surges on fast idle, after even half a mile of driving the car will stall below 2000rpm and hiccup violently on light throttle openings and if stopped it may not even restart at all unless stood for a while. No engine lights and no fault codes in VAG-COM. Above 2000rpm the engine seems to hunt as if there is a slight misfire.

I always run the car on high octane fuel, it suffers with some oil consumption but no worse than before the problems started. It uses no coolant at all and was running absolutely fine. The temperature gauge never seems to move past a quarter and the engine seems slow to warm so the thermostat may have died during the very cold weather but I doubt that alone would cause the problems I'm seeing.

Anyone with relevant experience please help. Before this happened I only had the console bushes left to fix.

[tag1_uk]

I feel your pain having the same engine. Do a search for AUB. Common problems which should help you - give the breather hose a clean, it is prone to getting clogged with oil and mayonnaise, run some redex through the fuel tank, check the spark plugs for burning oil as the faults are likely to be due to piston ring issues. Finally it is worth pre-emptively changing the engine coolant temperature sensor as your problems seem worse when the engine is hot. Finally get a throttle body clean and realignment (need vagcom). Another thing to look into is the EGR valve.

[sepulchrave]

I feel your pain having the same engine. Do a search for AUB. Common problems which should help you - give the breather hose a clean, it is prone to getting clogged with oil and mayonnaise, run some redex through the fuel tank, check the spark plugs for burning oil as the faults are likely to be due to piston ring issues. Finally it is worth pre-emptively changing the engine coolant temperature sensor as your problems seem worse when the engine is hot. Finally get a throttle body clean and realignment (need vagcom). Another thing to look into is the EGR valve.

Thanks for those tips, I am aware that the bores glaze on very badly on these engines due to often elderly first-owners driving them too gently early in their lives.

The oil consumption is not actually that bad and I can live with it, I think the valve stem seals may also be leaking which exacerbates the ring problem.

Have already done the TB clean and re-adaption so I know it's not that.

Any more ideas anyone?

[hap123ciu]

Maybe the water pump broke and made the cambelt to jump a tooth.

[sepulchrave]

Maybe the water pump broke and made the cambelt to jump a tooth.

Not likely but thanks for the input.

Have had all the spark plugs out and they're all very sooty suggesting the car is stuck in a cold start mode, plugs 2 & 3 showed slight signs of oil consumption but not enough to worry me.

Have blown back through the engine breather with the oil cap off and there is no blockage so I'm happy that it's clear.

I think the ECU engine temperature sensor is probably faulty so I'm going to change that first as per tag_1's advice.

I may then look to change the thermostat and housing when I have more time available if the sensor cures it.

People seem to get hung up about the AUB and oil consumption but it really isn't that bad and when the car is running well it's actually quite lively to drive when spanked properly.

[sepulchrave]

Ok, coolant temperature sensor was definitely duff, now that I've replaced it the gauge correctly reads half scale when the engine is warm.

Therefore the thermostat is fine. Which is nice.

The car now starts all the time, however it still pulses and occasionally stalls, it is less pronounced and may improve as the ECU remaps itself to suit the new coolant sensor.

It may also have a slight exhaust leak which will affect the tickover, getting that checked out later.

Thanks for the help chaps.

[MoggyTech]

Ok, coolant temperature sensor was definitely duff, now that I've replaced it the gauge correctly reads half scale when the engine is warm.

Therefore the thermostat is fine. Which is nice.

The car now starts all the time, however it still pulses and occasionally stalls, it is less pronounced and may improve as the ECU remaps itself to suit the new coolant sensor.

It may also have a slight exhaust leak which will affect the tickover, getting that checked out later.

Thanks for the help chaps.

If the exhaust leak is pre Lamda sensor, it can cause horrible problems. Throttle body clean and adaption, and all vacuum hoses would be next on my list.

[sepulchrave]

Oh dear, after an initial promising start the odious Furby has utterly disgraced itself again.

After an 'Italian tune' on the way home earlier the engine stalled at a roundabout and absolutely refused to restart.

Got a lift back to the car just now and it started fine and drove ok but stalled again as I was parking.

The exhaust turned out to be ok but the car is clearly misfiring and possibly overfuelling which is probably why it won't restart when hot.

Given that I have no fault codes on VAG-COM could this indicate plug leads breaking down?

MoggyTech, you may be onto something with the vacuum hose thing since I've noticed that the brake servo seems less efficient and sometimes seems to 'run out' of vacuum.

Oh, and pretty please no more "You need a new engine mate" nonsense just because it sips a bit of oil, these problems are definitely being caused by different gremlins.

[MoggyTech]

There is a common fault on the brake servo vacuum line, it splits and you get intermittent poor braking and running faults.

[sepulchrave]

Ok, it's all good news today, took the car out this morning, cold started without a problem, little bit lumpy but ok otherwise.

Drove half a mile, parked, got stuff, restarted fine, tickover better drove half a mile back expecting a stall as I went to park but all ok.

Realised that the hunting and missing was gone and that tickover was rock steady at 950rpm.

Decided to leave the car running to get properly warmed up and left it 20 minutes, went back out, temperature needle halfway, rad fan briefly cutting in then stopping.

Stopped engine and went for restart, no more problems!

I can only conclude that the new temperature sensor I fitted yesterday needed running time for the ECU to relearn the new engine temperature gradient.

Net result, happiness :yes:

[tag1_uk]

Glad it is sorted. Can't say I'm the greatest fan of this engine as it seems a bit flaky but then I wouldn't fancy the move within VAG group and elsewhere to smaller petrol engines with turbos/superchargers to make up the power (viz. the Fabia II VRS); even more things to go wrong :S

[MoggyTech]

Glad it is sorted. Can't say I'm the greatest fan of this engine as it seems a bit flaky but then I wouldn't fancy the move within VAG group and elsewhere to smaller petrol engines with turbos/superchargers to make up the power (viz. the Fabia II VRS); even more things to go wrong :S

Not to mention DSG

[sepulchrave]

Oh boy, here we go again.

After two days of flawless behaviour the Furby has done exactly the same again.

This time I at least have the CEL on so I have high hopes that I can extract a fault code which will point me in the right direction.

I find the electronics on this car frustrating beyond all human understanding, it as if there is a ghost in the machine.

I will post any findings/solutions here since I find searching these fora incredibly frustrating because so few users ever post again once they have resolution to their problem, that and the endless ploughing through the 'modified motah moronism' so heavily mixed in with any useful information.

I can't help thinking there ought to be separate forums for modders and those of us with real tech problems.

[MoggyTech]

I couldn't agree more. Fabia section does need a separate section for modifications and technical.

[sepulchrave]

My hopes of extracting fault codes proved well founded, print out follows:

Saturday, 12 March 2011, 16:01:24.

VCDS-Lite Version: Release 1.1

Control Module Part Number: 036 906 034 BK

Component and/or Version: MARELLI 4LV 3335

Software Coding: 00071

Work Shop Code: WSC 23018

VCID: 5CCB1773DF25

Additional Info: TMBND46Y2Y3061827 SKZ7Z0Y0527718

2 Faults Found:

16786 - EGR System: Excessive Flow

P0402 - 35-00 - -

17851 - Shareware Version. To Decode all DTCs

P1443 - 35-10 - Please Register/Activate - Intermittent

---------------------------------------------------------------------------

Saturday, 12 March 2011, 16:13:42.

VCDS-Lite Version: Release 1.1

Control Module Part Number: 036 906 034 BK

Component and/or Version: MARELLI 4LV 3335

Software Coding: 00071

Work Shop Code: WSC 23018

VCID: 5CCB1773DF25

Additional Info: TMBND46Y2Y3061827 SKZ7Z0Y0527718

1 Fault Found:

17584 - Bank1: O2 (Lambda) Correction Behind Catalyst: Control Limit Reached

P1176 - 35-00 - -

---------------------------------------------------------------------------

So after clearing DTC's I was actually able to start the car although it wouldn't idle properly.

Does anyone have any information on DTC 17851 please?

I can only assume the EGR valve is stuck open and is causing the misfire on cylinder number four and therefore the hot start problems.

I also presume that the Lambda probe is sooted up due to the overfuelling and will probably clean itself once the car is running properly again (if ever!)

I will strip and clean the EGR valve and pipes and see if it helps, is it possible to simply remove the link pipe and block the entry into the inlet manifold and run without it if I cannot get it to work?

[MoggyTech]

17851 P1443 EGR Valve Position Sensor Signal too low

[sepulchrave]

17851 P1443 EGR Valve Position Sensor Signal too low

Thanks for that Moggy.

I can definitely report that a thorough clean of the EGR valve has cured all the problems (for now!).

It was a pig of a job TBH, good thing the stainless EGR link pipe had a flexible bellows section which allowed me to deform the pipe enough to get the flange off the mounting studs.

If anyone else ends up doing this job DON'T bother removing the other end of the pipe from the manifold unless you absolutely have to, it's really hard to get it back on again due to access issues caused by the proximity of the gear linkage cables. Mine has a single coil pack and HT leads and this is also conveniently in the way of the hidden EGR link pipe clip along with the thermostat housing.

The valve itself was quite coked up and was clearly sticking open slightly, I used carb cleaner for rinsing but mostly had to scrape and chip the coke off because it was so hard.

My main focus of attention was the valve plunger rod and the valve seat, got the plunger rod nice and shiney until the valve moved up and down freely on and off it's seat. Checked the vacuum stub was not blocked or leaking then reassembled. Started first prod, warmed quickly, no hint of hunting or misfire, revved smoothly and settled quickly back to a rock steady idle. Result.

Moral of the story:

Don't imagine that a simple 'emissions control device' won't affect the running of your car much, in the case of these latest generation engines it is absolutely critical!

Mine was rendered completely unusable by this problem, suffering multiple issues with starting, running, fuel consumption, stalling and breakdowns.

Until the next thrilling instalment: FURBYS REVENGE!

Verdict: A brilliant little car spoiled by niggling quality issues and OAP first owners. Now for those console bushes......

[MoggyTech]

Well done, and yes a nasty awkward dirty job.

[Clunkclick]

Can you run the petrol engine on PD oil (Same VW spec number as oil for petrol engine), which has a lower ash content than petrol engine lubricating oil when burnt in the combustion chamber and therefore won't make as much sludge in a engine with worn rings/Valve stems ? Less sludge means a cleaner EGR valve and fewer rev counter stop bounces due to oil debris falling on the lambda sensors ?

Me BBZ 16v engine(Later version of AUB, but same problems)

Nick

Edited 15 March, 2011 by Clunkclick

[MoggyTech]

Can you run the petrol engine on PD oil (Same VW spec number as oil for petrol engine), which has a lower ash content than petrol engine lubricating oil when burnt in the combustion chamber and therefore won't make as much sludge in a engine with worn rings/Valve stems ? Less sludge means a cleaner EGR valve and fewer rev counter stop bounces due to oil debris falling on the lambda sensors ?

Me BBZ 16v engine(Later version of AUB, but same problems)

Nick

No, diesel oil contains far to many cleaning agents for use in a petrol engine. Handy as a flushing oil but that's about it.

[Clunkclick]

Strange, that's what I got charged for at my last main dealer service.

Nick

[hap123ciu]

Most of the VW 505.01 PD oil will have also VW 502.00 , which is good for the 1.4 16V . Most of the oil nowadays is made for both petrol and diesel.

Edited 16 March, 2011 by hap123ciu

[sepulchrave]

Well.....

I don't know whether to laugh or cry, FURBY HAS HIS REVENGE ALREADY!

It seems that every time I replace or clean a part the engine runs that little bit better than it ever has before, but after a random interval the problems return.

This time I have no CEL, yet the symptoms are identical again.

I'm rapidly getting to my wits end with this car and fully intend offing it as soon as I do get it running right, I can't live with this level of random unreliability.

I hate being beaten by a dumb car but pragmatism intrudes and I must have reliable transport.

Any helpful, informed contributions welcomed.

The whole AUB, BBZ, 'oil consumption' thing really is a red herring, any current owners REALLY need to get past it and delve deeper to find the actual problem.

I can't give up now, I HAVE to fix it.

[MoggyTech]

Well if it were me, I would replace the fuel pump relay, and engine speed sensor (G28), or threaten it with a very large lump hammer. After that I would try a throttle body, or strip the head down and look for sticking/burnt valves, and valve spring length.

[sepulchrave]

Well if it were me, I would replace the fuel pump relay, and engine speed sensor (G28), or threaten it with a very large lump hammer. After that I would try a throttle body, or strip the head down and look for sticking/burnt valves, and valve spring length.

Liking the sound of the fuel pump relay, tell me more please, like, where is it located?

Do you mean the crank sensor or the cam sensor?