1.9tdi pd105 surging

[Kalibrgun]

Anyone got ideas what could be wrong. Picked a Octavia up today with the 1.9tdi pd105 and 1st and 2nd gear pulls perfect into 3rd above 2800/3000rpm it starts hesitating all the way through the rest of the gears above 2500rpm. I've disconnected maf no change and disconnected egr vac pipe and plugged no change (both back how they should be) could it be maf sensor or should I be looking more turbo ? I need to get this sorted for the weekend as we're going away on a long journey 🙈

[Guest]

Surging or hesitating, which one is it?

 

Almost everyone else is going to tell you to scan it to see if there are codes stored so I'll say likewise, it may give you a better understanding of the issue.

 

Intermittent hesitation in my experience was an injector connector becoming loose with wear (common on old PDs), easily fixed at no cost.

 

I endured this for months, it began as a slight and brief one off misfire, gradually increasing in duration and intensity until it occurred frequently and it felt like I was driving with square wheels.  It was only at this late and severe state that it showed a misfire code for a particular injector.

 

Previously I had tried many things to rectify the problem without change but since the fix it's running like clockwork.

 

If you have a DMM disconnect the injector harness connector at the right hand/tandem pump side.  Probe the socket in continuity mode to find the ground pin (it will show a value with every other pin) then all 4 injector pins to ground noting the resistance, they should all be of a very low value.

 

I'm not saying this is your issue but it's a free diagnostic that may eliminate one possible cause.  I will say that the engine temperature and severity of this particular fault have an influence on the results you get measuring the injector harness, A cold engine with obviously loose injector wiring connector (female spade) is easier to diagnose than a connector that's still a bit tight and the engine is hot.

[Kalibrgun]

5 hours ago, MicMac said:

Surging or hesitating, which one is it?

 

Almost everyone else is going to tell you to scan it to see if there are codes stored so I'll say likewise, it may give you a better understanding of the issue.

 

Intermittent hesitation in my experience was an injector connector becoming loose with wear (common on old PDs), easily fixed at no cost.

 

I endured this for months, it began as a slight and brief one off misfire, gradually increasing in duration and intensity until it occurred frequently and it felt like I was driving with square wheels.  It was only at this late and severe state that it showed a misfire code for a particular injector.

 

Previously I had tried many things to rectify the problem without change but since the fix it's running like clockwork.

 

If you have a DMM disconnect the injector harness connector at the right hand/tandem pump side.  Probe the socket in continuity mode to find the ground pin (it will show a value with every other pin) then all 4 injector pins to ground noting the resistance, they should all be of a very low value.

 

I'm not saying this is your issue but it's a free diagnostic that may eliminate one possible cause.  I will say that the engine temperature and severity of this particular fault have an influence on the results you get measuring the injector harness, A cold engine with obviously loose injector wiring connector (female spade) is easier to diagnose than a connector that's still a bit tight and the engine is hot.

Im not 100% which one it just feels like the car is holding back a split second then a bit of power a load of times in a row real fast the higher up the rev range the more it seems to be 

[Kalibrgun]

Update I've not had time to do much today except swap a maf sensor off a pals car didn't make a difference. When the car was cold few min from start it didn't start doing it until up near temp.

[mac11irl]

try it with the maf  unplugged, not just swapped over. doing that forces the car to assume a preset air flow rare and around that. it might not be "correct" but it should smooth out the rough/lumpy bits IF the maf is the problem.

 

 

[JulianS]

Could it be fuel starvation? Change the fuel filter and note if the electric in tank booster pump is working.....

[Kalibrgun]

23 hours ago, mac11irl said:

try it with the maf  unplugged, not just swapped over. doing that forces the car to assume a preset air flow rare and around that. it might not be "correct" but it should smooth out the rough/lumpy bits IF the maf is the problem.

 

 

No change with that it's coming up with p0102 code 

42 minutes ago, JulianS said:

Could it be fuel starvation? Change the fuel filter and note if the electric in tank booster pump is working.....

I've had it plugged in its coming up with p0102 code 

[JulianS]

3 minutes ago, Kalibrgun said:

No change with that it's coming up with p0102 code 

I've had it plugged in its coming up with p0102 code 

Isn't that just because you ran it with the MAF disconnected?

[Kalibrgun]

1 hour ago, JulianS said:

Isn't that just because you ran it with the MAF disconnected?

No we cleared the codes and took it for a drive it came back on 

[Guest]

What's the air filter like?

[Kalibrgun]

2 minutes ago, MicMac said:

What's the air filter like?

Looks quite clean to be fair not black or ****ted up 

[Guest]

Air inlet at EGR coked up?

 

Mind you if it's hesitating under sustained high fuel demand situations it could be a dirty diesel filter impeding flow.

[Kalibrgun]

1 hour ago, MicMac said:

Air inlet at EGR coked up?

 

Mind you if it's hesitating under sustained high fuel demand situations it could be a dirty diesel filter impeding flow.

It will fly up to redline in 1st and 2nd and not do it just 3rd gear up to 6th

[mac11irl]

its a lot easier for the engine to get up to the redline in 1st and 2nd though, its not under the same resistance through the gearing, so the issue mught be much more subtle/ unnoticeable in the ose lower gears.

have a look at your fuel filter.....

 

 

have you recently changed fuel supplier? it has this been going on long enough to not be "bad fuel" linkable to one specific filling station?

[Kalibrgun]

12 hours ago, mac11irl said:

its a lot easier for the engine to get up to the redline in 1st and 2nd though, its not under the same resistance through the gearing, so the issue mught be much more subtle/ unnoticeable in the ose lower gears.

have a look at your fuel filter.....

 

 

have you recently changed fuel supplier? it has this been going on long enough to not be "bad fuel" linkable to one specific filling station?

Im not sure I've just bought the car. I use either Esso or BP I've put some miller's oils eco max additive in to try give things a clean and not a puff of smoke out the back

[-mike-]

19 hours ago, JulianS said:

Could it be fuel starvation? Change the fuel filter and note if the electric in tank booster pump is working.....

 

My 2.0 tdi (bkd) did have this issue and it had the same symptoms. First and second were fine, third it really felt like it hit a wall and then carried on as the revs went up. In my case, it was the tandem pump, however - it's worth checking that the in tank pump is working (should be able to hear it prime when you turn the ignition switch to the point before start. My car won't run for long without the in tank pump working but I'm not sure how the 105 behaves without it. 

[Guest]

The lift pump will be fine otherwise it wouldn't start, it only runs for a couple of seconds when the ignition is turned on to prime the fuel filter housing.

 

Once the engine is running the tandem pump draws fuel through from the filter.

 

Any fuel flow restriction by a dirty filter will starve the engine when demand exceeds available supply.

Edited 23 January, 2022 by MicMac

[JulianS]

You could do worse than have a look here. It spells out pretty well how the lift pump, eductor and other parts of the system work. The problem you have could relate to an issue here:

 

https://forums.tdiclub.com/index.php?threads/2005-bew-pd-lift-pump-operation-and-internals.225672/

[Kalibrgun]

I've had lift pump issues before on other cars (landrover and jeep) and it's nothing like the symptoms I've got now

[JulianS]

22 minutes ago, Kalibrgun said:

I've had lift pump issues before on other cars (landrover and jeep) and it's nothing like the symptoms I've got now

Remembering that the 1.9pd has a fairly elaborate system back there in the tank that looks like it can start throwing problems especially when the fuel gets below a certain level and the eductor system has to work. One design ''feature'' of the pd engine is all that fuel that travels through the cylinder head, it heats it up like hell, hence the fuel cooler and the funny plumbing in the tank.