Octavia TDI 110 Engine hesitation or Jerk

[GreenMeanie]

Hello everyone,

I've not had much to say on this forum before, mostly because my car's been fairly reliable up to this point...

Perhaps someone could shed some light on this engine issue i've been having. I have a 2002 Octavia 110 Elegance TDI with 165K. I look after it for the most part, use the expensive longlife oil, get the cambelt done on time etc. It gets driven up & down the motorway most of the time so has a fairly easy life. It starts a bit like a tractor and chucks out a bit of diesel muck under hard acceleration, but I think thats typical.

On the way to work yesterday, I was accelerating from 75 to 80 on the cruise control and got a noticeable regular engine hesitation or jerk. I disengaged cruise and tried to do the same with the throttle and the same thing happened. A slight hill came up and the car didn't want to go up, the speed dropped to 60 and the car kept jerking. Then the traction control light came on (Yellow trangle inside a circle - The same as when you press the ASR button). No, I wasn't driving on snow!

I found the only way I could drive it was to use the throttle really really gently. On slower roads, regardless of gear if I put my foot down more than 20% the car would hesitate and reluctantly pick up speed. It gets worse the higher gear and higher load you put the car under. If it were a 2-stroke go-kart i'd say it was running way too lean, or misfiring.

I stopped the car and had a look under the bonnet and nothing looked out of place. Re-started the car and the TCS light had gone out. Drove off down the road and the same issue again.

As for a cause, i'm pretty certain the TCS lamp coming on is an effect rather than a cause, as I develop TCS systems for a living and normally when the controller detects a fault, like the engine is misbehaving it shuts down and puts the lamp on. If it were a wheelspeed sensor or something I would expect the ABS not to work, but it works. This makes me think its an engine issue but I could be wrong.

Reading around on this forum, it sounds to me as though it could be sticky turbo vanes, so I tried the Mr Muscle Oven cleaner as per the (excellent) guide. When pressing down on the actuator linkage it felt pretty good, obviously the spring is stiff but it didn't feel gritty or stuck. When I took the car out for a spin after a 2 hour soak, I did a gentle warm up and then when the coolant hit 90 did some hard accelerations and all was well - happy days.

However, on the way to work again today its done the same thing. It only does it when the engine is hot (i.e. it's been 90 for a good 10 minutes). When the engine is cold it's fine, likewise the idle is fine. Incidentally, recently before the issue I'd been thinking how good the bottom end torque was, which made me think it could be turbo related.

Anyway, I'm a bit stuck now. Any suggestions?

I'm thinking maybe fuel filter or MAF next, it hasn't had a fuel filter for about 40K and the problem is worse at higher revs/ torque demand so will try this first.

Something else that may be relevant/irrelevant is for the first time in a year or so the car sat doing nothing for a week in the snow whilst I was abroad. First time I ran it I start to get issues. The other thing that made me think turbo, is that because of the snow the TCS has been working occasionaly and these work by killing engine power in conjunction with the brakes, I know from my work that this sends all sorts of unburnt nastiness into the turbo & cat.

Anybody around Aylesbury way with a fault reader?

Thanks in advance

Cheers

Phil

[dieselV6]

Except possible bad fuel or no air, your self diagnosis seems to work for you

(Unlikely, but a good starting point) Clear air intake from snow, it goes into the wheel well.

Unplug the MAF first and see if the symptoms mostly go away. If they do, you need a new MAF, if they don't go away, plug the MAF back in.

Refuel (insufficiently winterized diesel in the tank is possible given the cold outside).

Or even better, adding some pure isopropanol (rubbing alcohol, or IPA) into the tank helps getting rid of water and dissolving waxes if any. No more than 1% (a pint perf full tank), and must be 95%+ pure, preferably 99% (lots on Ebay).

Note most injector cleaners also contain IPA, but many have biodiesel too so are more risky at low temps.

Only then change fuel filter.(on account of winter weather now, could be clogged with wax, especially if fuel was dodgy).

Last year I left the UK in late February, and went for a -20deg C - -30degC drive to Europe, having read about lots of frozen diesels on some motorway in mid-Germany. I ended up adding rubbing alcohol to the last tank of the trip just to be sure the car will run fine a week later for the trip back. And It did work just fine, right after I dug the car out of the mound of snow, in -20degC outside

Edited 22 January, 2013 by dieselV6

[trundlenut]

It would also be worth getting the car checked for fault codes with VCDS.

[pauldazzle]

Diagnostics with VCDS/Vagcom needed.

[dieselV6]

VCDS would be nice, but from OP description he does not seem to have access to one.

Also, neither partly clogged fuel filter nor dodgy MAF produce any codes on ASV engine, while already producing symptoms described.

MAF is easy enough to check by unplugging it, and there were already posts this year on same symptoms and the fuel filter, it's quite cold outside and poor diesel tends to wax..

Edited 22 January, 2013 by dieselV6

[KenONeill]

I'm suspecting the TPS, but it needs VCDS to confirm that.

[GreenMeanie]

Thanks all, using the diagnostics forum I'm hoping to hear back from someone with VAG-Com in my area.

Sounds like MAF would be an easy one to tick off, i'll give it a go tonight.

Interesting thing for me is the relationship to engine temp, car is fine cold, fine warm (needle on 90), but poorly hot (has been on 90 for 5mins).

I also read on another thread that the TCS system on this model looks at the MAF for something, which could explain why my TCS (ASR) lamp comes on when the issue occurs.

Thinking out loud here, I assume the TCS system needs to know how much engine torque is being produced to control slip. If there's no torque sensor on the car (is there?) then it must predict it based on fuel flow, air flow, rpm etc..

[trundlenut]

As far as I knew the ASR uses the ABS sensors to detect when one front wheel is spinning faster than the other and then applies the brake on the slipping wheel to sort things.

[pauldazzle]

Coolant temp sensor failure is one of the most common problems on VAG cars. Check to see if you have the old black type. If you have just replace it with a genuine revised VAG CTS as it will fail if it hasn't already.

[GreenMeanie]

Trundlenut, you're right - Traction control (ASR) does use the same wheel speed sensors as ABS and the brakes, but it (should!) also control engine power, otherwise you'd just smoke your brakes if done for long enough.

Where is the coolant temp sensor located?

[trundlenut]

It may cut the power, but you do have a differential so the power is transferred to the other side rather than trying to melt the brakes.

The CTS is on the right had side of the engine (looking into the engine bay from the front) there are pictures showing it's location posted by mbames - try a search. The original ones are black, the newer are green. It has a plug with four wires coming out of it. IIRC correctly it is rear of one of the coolant pipes.

[pauldazzle]

The ECU will only throw a code if the CTS goes open circuit or intermittent. So it may not be the cause of the EML coming on.

At the risk of repeating myself for the zillionth time on VAG forums.

The CTS has 2 separate outputs. One to the temp gauge & the other to the ECU. The black CTS's are notorious for just one output failing resulting in either the temp gauge not working or becoming erratic. Or more seriously the ECU getting incorrect temp readings, which causes the ECU to fuel incorrectly. This often results in poor hot or cold staring & rough idle/running problems. Trouble is compounded by the fact that as long as the ECU is getting a reading from the CTS it won't throw a code. VAG had so many problems with the black CTS that they revised the part to what is commonly referred to as the green CTS.

WARNING

Experience from many VAG car owners including myself is that replacing with a genuine VAG CTS is the only fix. Aftermarket pattern part CTS's rarely work correctly or at all. Same with MAF's anything other than VAG & you'll be buying twice!

[mbames]

The CTS is on the right had side of the engine (looking into the engine bay from the front) there are pictures showing it's location posted by mbames - try a search.

Here you go. I would either go with MAF, CTS, n75 or maybe even a sticky turbo (but I would expect limp after the first big stutter for the latter two).

[GreenMeanie]

Thanks All,

Hopefully, I've arranged a diagnostic read for later on today so will see what comes up before changing sensors (mindful of your comment pauldazzle about the CTS)

As a bit of an experiment last night on the way home I drove 90% of the way (Motorway-ARoad and Town) like a granny, never going above 2000RPM, accelerating with all the verve of a sloth getting out of bed. Then for the last 5 miles or so drove it like I stole it and there were no engine issues!

[yesiamtom]

Sometimes you need to give it a good thrashing with the diesel. Mines mostly being used for local trips atm. On a 1 hour run it usually registers about 58 mpg. On the return run it gives 60 easily and 62 if i try. Once its warm on the first leg I usually boot it a few times off roundabouts etc when I get to my destination. The mpg read is taken before that though.

[GreenMeanie]

Right then, massive thanks to vrsPhil. This is why my car is poorly

17664 engine coolant temp sensor open circuit - intermittent

17656 start of injection timing control deviation - intermittent

01221 Crash sensor side airbag fault

Will get a new coolant temp sensor (of the new type) and report back.

As for 17656, anybody know what this could be? It cleared and didn't come back on a re-start.

And slightly off topic, anybody know where the crash sensor is?, I thought something like this might come up as the airbag light is on.

[VRSPhil]

Phil, FYI, I found this...

"17656/P1248/004680 - Start of Injection Timing Regulation: Control Deviation

Possible Symptoms

Loss of Power at high Engine Speeds

Engine difficult to Start

Possible Causes

Start of Injection Timing Regulation not OK

Injection Pump Control Range blocked/dirty (e.g. by Metal Particles)

Engine has stalled / ran out of Fuel recently

Wiring/Connectors from/to Injection Valve (N108) faulty

Possible Solutions

Check/Adjust Injection Start. See TDI Timing Checker

Check Fuel Supply

Check/Replace Fuse(s)

Check/Repair Wiring/Connectors from/to Injection Valve (N108)

Run Output Tests

Special Notes

Might by stored with other codes like 17654/P1246/004678.

When stored in the VW (9M/1J) Golf/Jetta or (1C) Beetle with the ALH engine code Tech Tip 23-02-03 may be helpful. The summary involves removing power at idle to the N108 Cold Start Injection Valve (Fuse 34 on those body styles) while monitoring Basic Setting group 000.2 which is shown under "Timing" when using the TDI Timing Checker. When power is removed from N108 the live reading should change to 255."

Copied from the RossTech Wiki here: http://wiki.ross-tech.com/wiki/index.php/17656/P1248/004680

I'm sure others will be able to offer further advice...

Cheers,

phil

[GreenMeanie]

Changed coolant temperature sensor to the new green type & also changed the fuel filter - Engine issues solved!

Thanks very much everyone.

[whitep]

Where is the cooland temperature sensor? In the radiator on on the engine block?

[trundlenut]

Where is the cooland temperature sensor? In the radiator on on the engine block?

Right hand side of the engine block (looking from the front). It is the back of one of the coolant pipes.

Sent from my Nexus 4 using Tapatalk

[mbames]

Where is the cooland temperature sensor? In the radiator on on the engine block?

 

See Post 13 above

[whitep]

See Post 13 above

Thought that was the one. Did that on the A3 when the gauge was reading wrong. My gauge is reading fine.

[trundlenut]

Thought that was the one. Did that on the A3 when the gauge was reading wrong. My gauge is reading fine.

The CTS has two circuits, one feeds the ECU, the other the dash. Typically the ECU feed goes pear shaped.

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[whitep]

The CTS has two circuits, one feeds the ECU, the other the dash. Typically the ECU feed goes pear shaped.

Sent from my Nexus 4 using Tapatalk

 

aah OK, worth a go then for a few quid.