Hi All,

 

I am hoping you can help me diagnose a cold running problem with my Octavia Scout.

I will endeavor to give you as much info as possible in this first post, but please let me know if you need any further info:

 

Car:

2015 Octavia Scout (Mk3)

2.0L Diesel - Manual

49k miles

No modifications

Regularly serviced

Owned for 2 yrs

Mostly used for short commute (6 miles each way), but does get plenty of longer runs (weekly).

 

Problem:

The car has started misfiring/hesitating within the first few minutes of driving, when the engine is cold.

Stalls occasionally (while misfiring), but mostly shows as a loss of power/drive, followed by sudden "kick" back in.

Issue goes away when engine gets up to temperature.

No issue starting the engine. Fires up on the key, first time, every time.

Idle is generally fine, but occasionally dips if sitting on tickover for a while (when trying to give engine chance to warm up)

Coil light sometimes flashes (while misfiring), but does not come on every time

Fault code P0322* registers when coil light flashes (Ignition/Distributor Engine Speed Input Circuit) - Diagnosed on OBDeleven

 

*My suspicion is that the fault code is being caused 'by' the misfire, rather than it being the source. However, I am happy to be corrected, if anyone knows any different.

 

Puzzler:

I can seem to drive around the worst of it, if I keep the revs up at around 1750-2000 rpm (however this is difficult at junctions and in heavy traffic...)

Problem is at its worst at around 1250-1500 rpm

 

Attempts to resolve:

Crank Position Sensor has been changed (did not help)

Fuel Filter and Fuel Pump have been checked (no issues)

 

I have the car booked back into the garage for Tue 22nd Dec. My mechanic wants to check the cambelt next, but I don't think this is the cause, due to the issue only happening when the engine is cold, driving at low revs.

I am having the cambelt changed anyway, as it is due on the 5 yr interval.

It is also due it's Major Service and MOT, which my mechanic is reluctant to do until he has managed to resolve the cold running issue.

 

I have read many forum posts discussing similar issues cold running issues, however none have been exactly the same as my issue.

Any help or advice will be greatly appreciated.

 

 

Many Thanks

 

 

Misfires can be devils to diagnose. They can be related to faulting glow plugs, faulty glowplugs relay. Blocked injectors, Faulty EGR, EGR cooler faulty fuel warmer etc.

As you have obdeleven you can monitor what the engine is doing by the live data function. That may point to a fault for you and help you out. It can also be a faulty engine temperature sensor giving incorrect readings.

I cant see the cambelt being the issue as that would present a fault even when warm and would run rough.

Thank you for your reply, Ecomatt.

 

I agree on the cambelt. It would definitely be rough all the time.

 

The bit that is puzzling me, is why I can drive around the problem if I keep the revs up...

 

I would have thought that a faulty/failing electronic component wouldn't necessarily care what the revs were doing(?)

If the only fault cod.e relates to P0322 ( crank sensor ) would have thought the problem must come from there.

 

It only sends a pulse to the ECU at every revolution of the engine.

 

As you've changed the sensor I'd be checking the wiring back to the ECU.

 

Disconnect both ends & check the wiring for any earths or stray voltages & check the loom for any rubbing/ chafing.

Replace the 3 wires from the ECU to the crankshaft sensor then reassess the fault.

3 hours ago, PipH said:

If the only fault cod.e relates to P0322 ( crank sensor ) would have thought the problem must come from there.

 

It only sends a pulse to the ECU at every revolution of the engine.

 

As you've changed the sensor I'd be checking the wiring back to the ECU.

 

Disconnect both ends & check the wiring for any earths or stray voltages & check the loom for any rubbing/ chafing.

 

1 hour ago, James@Pentagon_Seat said:

Replace the 3 wires from the ECU to the crankshaft sensor then reassess the fault.

Thanks both. Will give it a check.

 

Would this account for the fact that it seems to be ok above 1750 revs?

Unwanted resistance on that particular part of the loom can cause all sorts of unusual issues.

I would definitely be looking at Glow-Plugs. These are needed to assist with cold running engine. However, would also defer to @James@Pentagon_Seat  The crank sensor fault is likely. The problem is probably an electrical one in so much the sensor is Open-Circuit when cold (failure) with it 'fixing' itself when hot. 

2 minutes ago, varaderoguy said:

I would definitely be looking at Glow-Plugs. These are needed to assist with cold running engine.

 

Unlikely, once the engine has fired once the compression ignition cycle is self sustaining, they are needed to start and also play a part in reducing emissions in the first minute or two.

4 minutes ago, J.R. said:

 

Unlikely, once the engine has fired once the compression ignition cycle is self sustaining, they are needed to start and also play a part in reducing emissions in the first minute or two.

OP stated that the fault experienced had the glow-plug light on. Glow-Plugs do fail. I still maintain that it is worth checking. An electrical resistance test with a multimeter will determine high-resistance. Admittedly, the CANBUS should be logging this condition. Misfiring faults can produce a multitude of errors. @spikeybrumey was there on the P0322 fault showing or where there other faults too?

 

P0322 - Ign./Distributor Eng.Speed Inp.Circ.
No Signal 

 

Helpful advice on Ross-tech site : http://wiki.ross-tech.com/wiki/index.php/16706/P0322/000802

 

 

 

1 hour ago, varaderoguy said:

OP stated that the fault experienced had the glow-plug light on. Glow-Plugs do fail. I still maintain that it is worth checking. An electrical resistance test with a multimeter will determine high-resistance. Admittedly, the CANBUS should be logging this condition. Misfiring faults can produce a multitude of errors. @spikeybrumey was there on the P0322 fault showing or where there other faults too?

 

P0322 - Ign./Distributor Eng.Speed Inp.Circ.
No Signal 

 

Helpful advice on Ross-tech site : http://wiki.ross-tech.com/wiki/index.php/16706/P0322/000802

 

 

 

P0322 was the only fault code and (once cleared) this does not show up every time. The code only logs when the coil light flashes and this only occurs if I have not been able to keep the revs up enough (at junctions or heavy traffic) to keep the worst of the juddering at bay.

1 hour ago, varaderoguy said:

OP stated that the fault experienced had the glow-plug light on. Glow-Plugs do fail. I still maintain that it is worth checking. An electrical resistance test with a multimeter will determine high-resistance. Admittedly, the CANBUS should be logging this condition. Misfiring faults can produce a multitude of errors. @spikeybrumey was there on the P0322 fault showing or where there other faults too?

 

P0322 - Ign./Distributor Eng.Speed Inp.Circ.
No Signal 

 

Helpful advice on Ross-tech site : http://wiki.ross-tech.com/wiki/index.php/16706/P0322/000802

 

 

 

Thank you. I will check the glow plugs and will have a read through the Ross-tech link.

7 minutes ago, spikeybrummy said:

Thank you. I will check the glow plugs and will have a read through the Ross-tech link.

The Ross-tech link points to a possible Engine Speed Sensor (G28) fault. As I have not worked on any modern VAG cars before (my last car was a mid-90's Rover Tourer...), could someone please tell/show me where the Engine Speed Sensor and Crankshaft Sensor (loom) are located? I have tried looking online, but can only find examples for Mk I or Mk II engines.

These days the glow plug light can represent the presence of any engine related fault. 

 

When a plug fails it will log a fault code. 

 

The crankshaft and engine speed sensors are one and the same. It lives in a little hole on the front of the engine. 

 

Oddly enough on modern VWG diesel cars it will be the engine management light that indicates a glow plug issue.

Edited 13 December, 20205 yr by James@Pentagon_Seat

Update: My car is now in the garage (local independent) and is awaiting a new fuel (tank) pump. Their diagnostics were flagging this up as an issue and when they looked for the part number, they noticed that there have been several variations on this pump over the years, leading them to suspect that there might be a historic issue with that pump.

 

It is due to be fitted on 4th Jan, as they are closed over the Xmas - New Year break. Hopefully this will address the issue, as it will be costing me the best part of £500. I do still think the crank sensor code is a bit of a red herring and is being caused by the engine stuttering, rather than being the root cause itself.

 

Has anyone else experienced issues with the fuel pump in the fuel tank?

On 11/12/2020 at 16:26, PipH said:

If the only fault cod.e relates to P0322 ( crank sensor ) would have thought the problem must come from there.

 

It only sends a pulse to the ECU at every revolution of the engine.

 

As you've changed the sensor I'd be checking the wiring back to the ECU.

 

Disconnect both ends & check the wiring for any earths or stray voltages & check the loom for any rubbing/ chafing.

 

On 11/12/2020 at 18:44, James@RRG_Skoda_Rochdale said:

Replace the 3 wires from the ECU to the crankshaft sensor then reassess the fault.

 

For anyone still following this issue, or anyone reading it historically:

 

The fuel pump (although it had a permanent fault logged against it) was not causing the stuttering. Further investigation found that the wires from the Crank Sensor to the ECU had been rubbing and had frayed, causing them to short (thank you PipH & James). Presumably only occurring when the engine was cold due to the surrounding area having contracted slightly allowing the wires to move. Once the engine was warm and everything had expanded slightly, the wires were held in place and the short did not occur.

 

The wires were replaced and my car is working perfectly, although (mainly due to the fuel pump) my wallet is now £650 lighter...  

...AND I've still got the service and cambelt to pay for(!)

Ah, the joys of car ownership.

32 minutes ago, spikeybrummy said:

 

 

For anyone still following this issue, or anyone reading it historically:

 

The fuel pump (although it had a permanent fault logged against it) was not causing the stuttering. Further investigation found that the wires from the Crank Sensor to the ECU had been rubbing and had frayed, causing them to short (thank you PipH & James). Presumably only occurring when the engine was cold due to the surrounding area having contracted slightly allowing the wires to move. Once the engine was warm and everything had expanded slightly, the wires were held in place and the short did not occur.

 

The wires were replaced and my car is working perfectly, although (mainly due to the fuel pump) my wallet is now £650 lighter...  

...AND I've still got the service and cambelt to pay for(!)

Ah, the joys of car ownership.

Hi, glad you finally got to the cause of the problem. Expensive process!