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53 plate Octavia - Intermittent lumpy idle, juddering acceleration, smell of fuel,


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Hi all,

 

This may end up being a long one, so I'll apologise for my length immediately. :)  I'm looking for reassurance really that I'm going the right way.  Money is tight (isn't it always?) and I have no car mechanical knowledge.  I will try to explain this as best I can.  Any responses would be gratefully appreciated.  Bear in mind, that apart from throttle body cleaning (mentioned later) my mechanic will be doing the work (when money allows) and I need to have things explained to me as if I were a 5 year old.

 

I have a stock 53 plate Octavia Elegance 4x4 1.8T which I'm in need of some assistance with.  I bought the car about two years ago (two previous owners) with 33k on the clock. Previous owners kept the car garaged and due to mobility issues didn't use it that much.  FSH on the car and in almost mint condition.  I've been very pleased with it up until recently.

Although still a pleasure to drive, it had since I bought it, want to give it the beans (and the turbo would kick in for a second) when I was accelerating out of a corner/junction, it would then jolt as the acceleration returned to normal.  Not too much of an issue I thought and lived with it.

At its next service I got my mechanic to check the codes and they came back with:

  • 17705 Pressure drop between turbo and throttle valve P1297 - Intermittent (I've read the sticky)
  • 17545 Fuel Trim bank 1 (Add) System too rich P1137 _

On 5th April 2016 on its latest full service the car had its Cam Belt replaced.

 

On 12th April 2016  I was driving to work and instructed the cruise control to accelerate to its previously set speed.  When it got to the required speed, the engine jolted, went into limp mode and I had to pull over at the side of the road.  The engine would not respond to depressing the accelerator pedal.  After turning the engine off and on again it was a bit lumpy but more or less fine.  That afternoon I managed to get Mr Mechanic to pull some codes (this is not using VAGCom kit).  The codes were as follows:

  • 17705 Pressure drop between turbo and throttle valve P1297 - Intermittent
  • 17545 Fuel Trim bank 1 (Add) System too rich P1137 _
  • 17743 Engine Torque Monitor 2 Control limit exceeded P1335 - Intermittent

 

On 18th April 2016 the MAF sensor was replaced.  This was something that I'd been meaning to do to address the first 2 fault codes (but didn't have the money for) and hoped that it had something to do with my breakdown on the 12th..  The fuel economy improved by about 3mpg on a 14 mile round trip and the instances of the turbo kicking in when not wanted/required was resolved.

 

A few days later after naively thinking that all was good in the world I was accelerating to overtake; revs were high (5K RPM) and the engine became very "laggy" as if the boost was kicking in and fading out.  The car misfired and ran like a bag of smashed crabs for a couple of days.

After reading more of the forum entries on Briskoda I established that my car may qualify for the recall and replacement of the coil packs under 28F7.   On 21st April 2016 I took it to a different garage than my usual mechanic's and they replaced coils 1, 2, & 4.  I was told that coil pack 3 had already been replaced (by a previous owner) and was a non genuine part and so did not qualify for replacement under warranty.

 

Since then, the car is drive-able 75% of the time, but when it runs like a dog, it really runs like a (three legged) dog; It misfires, lumpy idle, turbo kicking in and out on acceleration at high revs.  When the idle has been lumpy there has been a smell of fuel.  I'm not sure if I'm imagining it and it may be coincidence, but it seems that the car runs worse when the air conditioning is on full blast, cold.

 

The hoses have been checked by Mr Mechanic and he can't find anything wrong with them.  He took my car to a fellow mechanic who has "better kit than mine and should be able to dig deeper to find more codes if they're there" (see what I mean about needing to be spoken to like a 5 year old?!) :)  I'm guessing that he means the other guy has VAGCom kit.  Sods law, the car was running absolutely fine when connected to the kit. He did say that (one of?) the Lambda sensors was taking its time to close (or something like that) but wasn't so far out that he thought it could be problematic. When I picked up the car from regular Mr Mechanic, as soon as I got in it, started it up it and it was running like a chewed up cassette tape.

 

It seems that I can reproduce the symptoms some of the time by flooring it and giving it some beans.  Other times it will run fine for a few days even if I drive it like a 17 year old wearing a baseball cap backwards.  Getting the symptoms to appear and coinciding with getting other mechanic guy to be available to do live diagnostics on it is proving difficult.

 

Next step (unless advised otherwise):

I have ordered some carb cleaner and a replacement throttle body gasket and am hoping to attempt cleaning that out in the next week by following the guide found on this site.

 

After that, I'm not really sure what to do - N75 valve perhaps but don't want to keep chucking money at it.

Likelihood of it being a cambelt timing issue after it was replaced?

 

Any thoughts would be gratefully received.  

 

Apologies again for my length and thanks in advance.

 

 

 

 

 

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Got any air leaks?

Symptoms you describe I would say the list would consist of:

Air leak

Coil packs

MAF

N75

Coolant temp sensor

Most of which you have replaced. Beyond those I'd be looking to do some logging to pinpoint it further. The fuel you smell is unburned fuel from the misfire, or something could be amiss with the injectors...think I'd be looking at fuel delivery after crossing those off.

I'd probably try a new gen coil for that odd one out as a matter of course. In my old Seat my failing coil pack didn't throw a code and eventually it melted, if only I knew then what I know....

Lumpy idle is a big time symptom of air leak as are some of the codes and other things, get a smoke test probably before buying too many more parts mind.

Edited by YellowCar
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Got any air leaks?

Symptoms you describe I would say the list would consist of:

Air leak

Coil packs

MAF

N75

Coolant temp sensor

Most of which you have replaced. Beyond those I'd be looking to do some logging to pinpoint it further. The fuel you smell is unburned fuel from the misfire, or something could be amiss with the injectors...think I'd be looking at fuel delivery after crossing those off.

I'd probably try a new gen coil for that odd one out as a matter of course. In my old Seat my failing coil pack didn't throw a code and eventually it melted, if only I knew then what I know....

Lumpy idle is a big time symptom of air leak as are some of the codes and other things, get a smoke test probably before buying too many more parts mind.

 

Many thanks for your response and the information about the fuel smell - it seems to make sense even though I know sod all about cars.

I'm not sure if I have any air leaks or where they would come from.

It's interesting that you say your failing coil pack didn't throw a code before it died. I understand that it may be possible to swap the coil packs over and see if the problem persists.  I was of the understanding that if a coil pack was failing and threw a code (the crucial bit which yours didn't do!) it would be easy to eliminate.  

Do you think that replacing the coil pack would be the next logical step after cleaning the throttle body on the weekend?  I guess I'm asking whether you think it would be cheaper to do the smoke test first or the replacement No.3 coil pack?  What is, and what would a smoke test tell me - where a potential leak was coming from? (5 year old speak remember.)

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As per Yellowcar.

I would replace the odd coilpack with a gen VAG part first.

If that doesn't solve it, check all the vacuum, & PCV pipes. A visual check is not enough as the braided hoses often split inside the braided cover. There's also a pipe (commonly referred to as the S pipe) under the inlet manifold that is notorious for splitting & very difficult to see. Listen for hissing with the engine at idle that's a dead give away of a split pipe. Oil splatter is another sign. Smoke test is the best option.

Coolant temp sensor, check to see if it's the original black CTS fitted,  & change it for a genuine revised green VAG part if it is regardless as the black CTS will fail for sure.

Cleaning the throttle body often solves the 17705 code, & is worth doing regardless.

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Many thanks for your response and the information about the fuel smell - it seems to make sense even though I know sod all about cars.

I'm not sure if I have any air leaks or where they would come from.

It's interesting that you say your failing coil pack didn't throw a code before it died. I understand that it may be possible to swap the coil packs over and see if the problem persists.  I was of the understanding that if a coil pack was failing and threw a code (the crucial bit which yours didn't do!) it would be easy to eliminate.  

Do you think that replacing the coil pack would be the next logical step after cleaning the throttle body on the weekend?  I guess I'm asking whether you think it would be cheaper to do the smoke test first or the replacement No.3 coil pack?  What is, and what would a smoke test tell me - where a potential leak was coming from? (5 year old speak remember.)

I would probably replace that coil pack whatever happens as a matter of course, it may solve the problem. However it does sound like air leak/s to me, pipework on these is very susceptible and at the age now where that kind of stuff is just perishing.

You just need to find a garage who has got the equipment, which shouldn't be impossible where you are. Basically they induct pressurised combustion safe smoke and as it runs through the system will seep out of any wounds or splits and reveal the leak.

You could also try visual checks yourself, the breather pipes to the top right of the block, from that breather set up down to the 90 degree elbow at bottom of dipstick tube, pipework and joins from turbo to cooler, cooler itself, cooler to throttle body.

Cleaning throttle body and replacing the gasket will certainly help. Unbolt it but leave it plugged in to avoid any re calibrating hassle. I cleaned mine plugged in with a drip tray underneath, ignition on (not engine!) and Mrs pressed throttle to open the flap to allow cleaning right through.

Smoke test shouldn't cost too much

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As per Yellowcar.

I would replace the odd coilpack with a gen VAG part first.

If that doesn't solve it, check all the vacuum, & PCV pipes. A visual check is not enough as the braided hoses often split inside the braided cover. There's also a pipe (commonly referred to as the S pipe) under the inlet manifold that is notorious for splitting & very difficult to see. Listen for hissing with the engine at idle that's a dead give away of a split pipe. Oil splatter is another sign. Smoke test is the best option.

Coolant temp sensor, check to see if it's the original black CTS fitted,  & change it for a genuine revised green VAG part if it is regardless as the black CTS will fail for sure.

Cleaning the throttle body often solves the 17705 code, & is worth doing regardless.

 

Then the coil pack is what I will do after the attempt at cleaning the throttle body - for the sake of £15 quid I guess it is worth doing.

If it was a hose/pipe - would there be any reason as to why it would be so temperamental?  Would it not be playing up all the time?  I would have trouble identifying an inlet manifold, let alone an "S pipe" but I appreciate your description. :s  I've read about coolant temperate sure sensors being something to eliminate - and I think they're relatively cheap? <£30?  I guess I'd be hopeful if these were covered under some kind of warranty/recall?

Many thanks for taking the time to respond.

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I would probably replace that coil pack whatever happens as a matter of course, it may solve the problem. However it does sound like air leak/s to me, pipework on these is very susceptible and at the age now where that kind of stuff is just perishing.

You just need to find a garage who has got the equipment, which shouldn't be impossible where you are. Basically they induct pressurised combustion safe smoke and as it runs through the system will seep out of any wounds or splits and reveal the leak.

You could also try visual checks yourself, the breather pipes to the top right of the block, from that breather set up down to the 90 degree elbow at bottom of dipstick tube, pipework and joins from turbo to cooler, cooler itself, cooler to throttle body.

Cleaning throttle body and replacing the gasket will certainly help. Unbolt it but leave it plugged in to avoid any re calibrating hassle. I cleaned mine plugged in with a drip tray underneath, ignition on (not engine!) and Mrs pressed throttle to open the flap to allow cleaning right through.

Smoke test shouldn't cost too much

 

Yet more wonderful advice - Thank you very much.  As per my previous post, I'm not sure what a breather pipe even looks like.  I think I've just about figured out where the dipstick is....(no comment.)

Thanks again. 

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Then the coil pack is what I will do after the attempt at cleaning the throttle body - for the sake of £15 quid I guess it is worth doing.

If it was a hose/pipe - would there be any reason as to why it would be so temperamental?  Would it not be playing up all the time?  I would have trouble identifying an inlet manifold, let alone an "S pipe" but I appreciate your description. :s  I've read about coolant temperate sure sensors being something to eliminate - and I think they're relatively cheap? <£30?  I guess I'd be hopeful if these were covered under some kind of warranty/recall?

Many thanks for taking the time to respond.

Problem from a leaking pipe isn't necessarily consistent, it would depend on the type of leak. A leak round a coupler or clip would be more consistent, splits less so usually and will change with temperatures, not an exact science.

Inlet manifold runs along front of engine, throttle body on end of it, the usual pipework suspects is a bit of spaghetti junction underneath. The S pipe runs into a harder 90 degree elbow.

I'd get a genuine coil which won't be too cheap, but yes cts should be well under 30 quid.

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Yet more wonderful advice - Thank you very much.  As per my previous post, I'm not sure what a breather pipe even looks like.  I think I've just about figured out where the dipstick is....(no comment.)

Thanks again.

As you look at the engine with cover off, to the top right is a Y shaped pipe, one leg of which goes down, that's where it joins the S pipe which goes down below inlet towards dipstick.

If you Google vw 1.8t split pipes you should find some useful images.

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Problem from a leaking pipe isn't necessarily consistent, it would depend on the type of leak. A leak round a coupler or clip would be more consistent, splits less so usually and will change with temperatures, not an exact science.

Inlet manifold runs along front of engine, throttle body on end of it, the usual pipework suspects is a bit of spaghetti junction underneath. The S pipe runs into a harder 90 degree elbow.

I'd get a genuine coil which won't be too cheap, but yes cts should be well under 30 quid.

Thank you.  So.....:

  1. Throttle body cleaning (already paid for)
  2. Replacement No.3 Coil pack
  3. Smoke test
  4. Coolant Temperature Sensor

Sounds like a(n economic) plan?  

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As you look at the engine with cover off, to the top right is a Y shaped pipe, one leg of which goes down, that's where it joins the S pipe which goes down below inlet towards dipstick.

If you Google vw 1.8t split pipes you should find some useful images.

Cheers.  I'll do that.  

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Thank you.  So.....:

  • Throttle body cleaning (already paid for)
  • Replacement No.3 Coil pack
  • Smoke test
  • Coolant Temperature Sensor
Sounds like a(n economic) plan?

Yes. And as pauldazzle says pay close attention to dipstick tube, they get brittle and get knocked when working round there and crack easily. Might be worth having a replacement ready for the sake of a few quid.

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Broken dipstick holder is another suspect for lumpy idle.

 

Yes. And as pauldazzle says pay close attention to dipstick tube, they get brittle and get knocked when working round there and crack easily. Might be worth having a replacement ready for the sake of a few quid.

Oodafoughtit?  I wouldn't have even thought to take that into consideration.  Would that also account for "lagging" (can you tell I work in IT?) at high revs?

Thanks to you both.  I will keep this thread updated as I investigate until resolution/sale of the car!

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The smoke test is a must.

The way the engine works is by metering the volume of air coming in (by maf).

The air then gets pressurised by means of a turbo and is delivered -past the throttle - to the combustion chambers. There it mixed with fuel, which itself is metered in proportion to the air that was originally measured. Problem is that, somehow, the combustion process finishes with unburnt fuel. Too much fuel is left over. Or, not enough oxygen was available to complete the combustion.

Hence 2codes:

System too rich and

Pressure drop between turbo and throttle.

The lambda sensor (a probe on the exhaust pipe) has told the ECU it did not find any oxygen left in the exhaust gasses.

Rubber hoses become porous after while and those clever German engineers know that. The have added to the ECU (the car's CPU) has algorithms to compensate for deterioration and deviation

It's called Adaptation. The ecu can trim the fuel supply or even add a touch of fuel. Hence why the lamda sensor is so important.

But only to a certain point, so as not to mask a genuine issue with potential implications.

So as long as you drive sensible the ECU will compensate and allow you to operate the car, but, when you give it the beans, you exacerbate the issue and... computer says no (more).

A smoke test should reveal which pipe between the turbo outlet and throttle body is leaking. It is a fiddly job and a reason why most of us end up replacing them with uprated items.

Replacing the CTS is also a matter of course, though use a genuine item.

Sticky throttle body could be, although unlikely.

If all else fails, find a fellow brisky member with vag com and perform some logging.

Good luck and keep us posted

Edited by G-slave
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The smoke test is a must.

The way the engine works is by metering the volume of air coming in (by maf).

The air then gets pressurised by means of a turbo and is delivered -past the throttle - to the combustion chambers. There it mixed with fuel, which itself is metered in proportion to the air that was originally measured. Problem is that, somehow, the combustion process finishes with unburnt fuel. Too much fuel is left over. Or, not enough oxygen was available to complete the combustion.

Hence 2codes:

System too rich and

Pressure drop between turbo and throttle.

The lambda sensor (a probe on the exhaust pipe) has told the ECU it did not find any oxygen left in the exhaust gasses.

Rubber hoses become porous after while and those clever German engineers know that. The have added to the ECU (the car's CPU) has algorithms to compensate for deterioration and deviation

It's called Adaptation. The ecu can trim the fuel supply or even add a touch of fuel. Hence why the lamda sensor is so important.

But only to a certain point, so as not to mask a genuine issue with potential implications.

So as long as you drive sensible the ECU will compensate and allow you to operate the car, but, when you give it the beans, you exacerbate the issue and... computer says no (more).

A smoke test should reveal which pipe between the turbo outlet and throttle body is leaking. It is a fiddly job and a reason why most of us end up replacing them with uprated items.

Replacing the CTS is also a matter of course, though use a genuine item.

Sticky throttle body could be, although unlikely.

If all else fails, find a fellow brisky member with vag com and perform some logging.

Good luck and keep us posted

Wonderful response.  Makes slightly more sense now.  Thanks muchly for taking the effort to explain.

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The smoke test is a must.

The way the engine works is by metering the volume of air coming in (by maf).

The air then gets pressurised by means of a turbo and is delivered -past the throttle - to the combustion chambers. There it mixed with fuel, which itself is metered in proportion to the air that was originally measured. Problem is that, somehow, the combustion process finishes with unburnt fuel. Too much fuel is left over. Or, not enough oxygen was available to complete the combustion.

Hence 2codes:

System too rich and

Pressure drop between turbo and throttle.

The lambda sensor (a probe on the exhaust pipe) has told the ECU it did not find any oxygen left in the exhaust gasses.

Rubber hoses become porous after while and those clever German engineers know that. The have added to the ECU (the car's CPU) has algorithms to compensate for deterioration and deviation

It's called Adaptation. The ecu can trim the fuel supply or even add a touch of fuel. Hence why the lamda sensor is so important.

But only to a certain point, so as not to mask a genuine issue with potential implications.

So as long as you drive sensible the ECU will compensate and allow you to operate the car, but, when you give it the beans, you exacerbate the issue and... computer says no (more).

A smoke test should reveal which pipe between the turbo outlet and throttle body is leaking. It is a fiddly job and a reason why most of us end up replacing them with uprated items.

Replacing the CTS is also a matter of course, though use a genuine item.

Sticky throttle body could be, although unlikely.

If all else fails, find a fellow brisky member with vag com and perform some logging.

Good luck and keep us posted

Oh..and forgive me for another potentially numpty question: I've looked online for "car engine smoke test" and the results have come back with very little.  Is this the term I should be searching for or is there another technical name for it?

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Oh..and forgive me for another potentially numpty question: I've looked online for "car engine smoke test" and the results have come back with very little. Is this the term I should be searching for or is there another technical name for it?

Look for Boost Leak Smoke Test [emoji6]

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To the OP, not sure what the term is, but essentially it is a smoke machine connected to a pressure pump.

The smoke is such that it takes time to reaxlct with oxygen, therefore it stays visible for a while and makes it possible to "see" a leak.

The cheap version is a smoke bomb (the ones used by chimney sweepers) and a tyre inflator, connected to your air intake (NOT YOUR MAF!!!).

Finally you need good lighting and torches.

Keep us posted

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Hi all. Update as promised:

Throttle body was cleaned today. It was quite minging in there.

Still no joy though.

So..what next? Cheapest first please! Coil pack 3, smoke test or CTS?

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Ok. It seems that finding a place in Wiltshire to do a smoke test is not as easy as it could/should be. Even the Audi/VW place couldn't recommend anywhere. Any suggestions? The closest place I've found is in Bucks: Autotorque, and I think they're an Evo specialist so may not even touch it. I haven't spoken to them yet as its well out of the way. Anyone have experience of a smoke test in Wiltshire?

So, in the meantime I'm planning to try and get another coil pack whilst trying to find a place to do a smoke test. Does anyone know of the right part number I should be looking for? I don't want to replace the coil pack with a generation that's likely to fail.

Has anyone had any experience of using skodaparts.com? Likely to be legit?

I got a price at a local skoda dealer (where my other coil packs were replaced under warranty) and it was £140(!) for the part and to fit. Is this something I could do myself? Is there a guide? The same place said the part was £40 so if I could save some money and do it myself I'd be happy.

I appreciate there's a lot of questions in this post. Your ongoing help and patience really is appreciated.

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