Hesitation and poor running

[r4c]

Had my octavia for about 4 months now and have so far done the Mr muscle clean on the turbo due to over-boost/limp mode, after running the car on average of 80 miles per day i notice some intermittent symptoms.... as follows

Hesitation - When Accelerating normal from standstill or working through the gears quickly all feels fine, if however i hold the gear before overtaking or accelerating from a slip road there is a very noticeable hesitation/flat spot around 2800 rpm lasting up to about 3200 rpm

MPG - When i got the car it used to say that i was averaging 56mpg Now this has dropped to 48-49 mpg and no matter how i drive i struggle to increase it. It seems that i get better mpg round town and as soon as i average 60-70 mph my average consumption plumits

Idling - 90% of the time it idles fine, other times the revs jump up and rest at 1200rpm for about 20 seconds and then falls back to normal

intermittent poor running - The car seems to run great for the first 5 mins after starting the car on a cold engine, as soon as i start warming the engine it seems very unresponsive. Low down boost seems fine but sometimes feels a bit gutless when needing to overtake. Again holding the revs and overtaking for example is not 100%

Strong diesel smell - I dont know if this is normal, i always thought the way the exhaust points down at the back the wind is blowing the fumes to the front of the car. When idling there is a very strong diesel smell, its that bad my wife will refuse to open the windows

I think thats everything

I checked all the vac lines and have noticed that on one of the pipes that run under the egr has been rubbing in its holder thing and has rubbed the pipe right down (not rubbed through yet) but is very thin and would expect it to split soon with the vacuum. It goes to a small sensor on the manifold.

Edited 20 September, 2012 by r4c

[octaviadan]

Hi and welcome to the forum!

Firstly have you done a code read on it on VCDS/VAG-COM? I would start with that which should give some indication of what could be going on.

This could be a various issues and by doing the code read first, this should help identifying the problem. Sounds as though this could be:

-MAF

-CTS

-N75

-restricted EGR/intake manifold

Strong diesel smell is definitely not normal. Have you checked all fuel lines? Does the car smoke especially when you boot it?

Dan

[r4c]

Hi and welcome to the forum!

Firstly have you done a code read on it on VCDS/VAG-COM? I would start with that which should give some indication of what could be going on.

This could be a various issues and by doing the code read first, this should help identifying the problem. Sounds as though this could be:

-MAF

-CTS

-N75

-restricted EGR/intake manifold

Strong diesel smell is definitely not normal. Have you checked all fuel lines? Does the car smoke especially when you boot it?

Dan

Thanks for the reply.

I have not had any codes read yet, will do that.... will see about getting the lead and software for checking.

The diesel smell is more from the exhaust side of it (not raw diesel smell) but a lot stronger than i would think is normal. If you open the car door the fumes are strong or when sitting in the car with the window open.

When i cleaned the turbo i also cleaned the egr, the actuator seems to have full travel . although is stiff i need to push down on it with a bar to get it to move, it wont move easily by hand.

[octaviadan]

Strong diesel fumes smell sounds as though it is running very rich so I think it could be a duff CTS, however a code scan should reveal this. Rather than trying to source a lead for VCDS, isn't there someone local on here who would scan it for you for a couple of beers? Where abouts are you situated?

[r4c]

I am in ayrshire

[octaviadan]

Lofty79 is in Perthshire but my geographical knowledge of Scotland is not great so not sure how local he is to you! I am sure that there is someone on here in Ayrshire who can help?

It might be an idea to edit the name of your topic to include 'TDI' - you will then attract the regulars with perhaps more knowledge of TDI issues than me!!

Dan

[octaviadan]

Just re-reading your posts, how did you clean the EGR? Did you remove it from the intake manifold? It would have been better to remove the intake manifold as well as if your EGR was caked, the intake manifold would be clagged up as well, restricting boost pressure into the engine. I am also wondering if you have removed some pipework when using the 'Mr Muscle' method to clean the turbo, you may have created an air/boost leak if all hoses/anciliaries have not been put back together quite right, so worth checking.

Dan

[r4c]

Hi dan, I removed the egr from the manifold and was full of carbon. I cleaned what i could of the manifold but did not remove.

The only thing i have noticed is one of the vacuum pipes is worn right down and is very thin wall.

Should the actuator arm be stiff as i have trouble pushing down on it by hand, i need to use a socket extension or screwdriver , i did work on it when i was doing the mr muscle method but could never free it better than it is now.

[octaviadan]

Hi dan, I removed the egr from the manifold and was full of carbon. I cleaned what i could of the manifold but did not remove.

The only thing i have noticed is one of the vacuum pipes is worn right down and is very thin wall.

Should the actuator arm be stiff as i have trouble pushing down on it by hand, i need to use a socket extension or screwdriver , i did work on it when i was doing the mr muscle method but could never free it better than it is now.

Really the intake manifold should be cleaned off the engine block as scraping the crud out in situ risks debris dropping into the engine with potential catastrophic results....

You maybe losing a bit of vacuum from that thin vac pipe but would'nt cause some of the issues you have been experiencing - maybe some underboosting but nothing else. Replace it anyway as a matter of course. Have you checked the rest of the pipework right back to the vacuum sphere? I had a very thin/weak pipe near to that.

Re the actuator arm, a strong resistance is normal as you are pushing against a strong spring in the actuator body so you will need a socket extension or screwdriver to move it. If it feels free through its travel then there is little carbon/rust present causing sticky vanes, if it feels 'gritty' or has some resistance through its travel then there is carbon/rust present which if bad enough can cause boost issues.

Another thing you could try is to unplug the MAF sensor to see if the car runs any better unplugged. This will cause a error code log when you read the codes with VCDS by doing this. If the car runs better then it is very likely that the MAF is goosed - this is a very common problem. There are loads of threads on here if you do a search.

Dan

Edited 22 September, 2012 by octaviadan

[r4c]

Yesterday due to a family emergency i driven the car like i stole it, thankfully everything is ok regarding the emergency but everything is not OK with the car. It was struggling bad... every gear a large hold back at 2800rpm all the way to the red line, the only way to restore the power was to change gear and stay under 2500.

I dont usually drive like that, the turbo low down is fine, then kicks in at 1900 up to 2600-2800 and bogs down......any Ideas?

I am not convinced a scan will show anything, after reading all the posts with similar problems and there being no fault code

[octaviadan]

Try unplugging the MAF and then take it out for a spin (one minute job). If it runs better then it is very likely that the MAF that is at fault, but this could be one of several issues causing your car not to perform.

It also sounds as though it could be sticky vanes in the VNT although you say that you have done the 'Mr Muscle' clean. I am wondering if it needs a further go as there is still some carbon is there or maybe some rust in there that could be causing it to stick (which Mr. Muscle won't remove!).

It took me ages to get mine right and I eventually replaced everything that can cause performance issues as previously listed - it really is a process of elimination. Skoda themselves have a reputation for replacing everything listed above until the car performs as it should!

Have a play over the weekend and see how you go on! It would be beneficial for a VCDS code scan though. Can anyone help r4c with a code scan? He lives in Ayrshire

Dan

[r4c]

Thanks for the reply dan, i had a feeling that i might need to start replacing random sensors. The car is going for an mot next week so i can see how the emmisions are, see if its running rich.

I have unplugged the maf and feels the same as limp mode.

Weird thing i have noticed, on motorways with a steady throttle and i reset mpg, the (average) consumption shows about 49mpg, and instant mpg is showing about 35mpg at 70mph on a very light throttle. if i go on back roads or round town i can average 53mpg. I know the mpg on the computer is not 100% reliable but why such a difference.... i would be expecting better mpg on a motorway going at a steady pace.

Before the mr muscle i would average about 58mpg everywhere and no matter how i drove..... i would never see it drop to the figures i get now, i was thinking because the turbo is working better that i am now using the turbo more often hence the lower mpg.

[octaviadan]

Ok, so I think that perhaps we can rule out MAF problems.

Re issues with fuel consumption, after the Mr. Muscle clean the turbo 'should' be running more efficiently, hence producing more boost so would need less fuel to make the car move, unless however you are constantly booting it...

My fuel consumption improved after my new (hence clean) turbo - about 2-3mpg overall. I do find though that motorway running does use slightly more than A road work as even if you are sticking to the 70 limit, generally the engine is revolving faster than a 60 limited A road. My daily commute of 35 miles each way typically achieves 65+mpg, whereas a constant motorway run at a steady 70 returns high 50's to low 60's. These figures are from the fuel computer and that does overread between 5-10mpg at times!

To me your problem sounds like a blockage somewhere either fuel or exhaust. Have you changed the fuel filter recently or run some fuel additive through? If not, that maybe worth a try. I found 'Silverhook' Diesel treatment very effective with mine. Also check the exhaust, that could be partially blocked, maybe by some carbon cleaned off the turbo??

Dan

Edited 30 September, 2012 by octaviadan

[andyaro]

hi,

my 02 octy vrs is doing the same however i haven't cleaned anything out. I've checked the fault codes and it is throwing up p0121 and I've just replaced my MAF sensor and I'm lead to believe its the throttle position sensor. However, I'm no expert just an amateur.

[Lofty79]

Right here we go.

to check vac hose leading to turbo, make sure you can see actuater, and get someone to start the engine, it should go down slowly when started

as said codes need to be read really....... but........

MAF still could be at fault, symptoms sound very similar to when mine was on the blink! and yes unplugged is like limp mode thats normal. This is where my money is!!!

Coolant temperature sensor is my second port of call - temperature related running issues suggest this to me. What is the temp gauge like? is it up to 90 than stays there?

I have a spare n75 i can post you for illimination.

My next move would be this to remove it from the equation:

http://www.ebay.co.u...#ht_1578wt_1039

cheap and if no difference, a spare is always worth having!

Edited 30 September, 2012 by Lofty79

[r4c]

Thanks for the replies, Yes i think i will order a MAF and see what happens, I have not replaced the fuel filter or used additives. After experimenting it only seems to happen on full or 3/4 throttle, hardly ever notice on part throttle "say - half way". You can actually (when hot) hold half throttle and put straight to the floor, it will then hesitate then pick up a bit and then hold back. It is intermittent, some days it feels fine and others its back to the way it was..... i cant seem to figure out when it will happen.

[Lofty79]

r4c I have pm'd you