1.8tdci jerking at 1800rpm

[Dennis the meance]

hi read various post on here regarding this prob and it normally point to injectors and the dreaded Siemens dodgy injectors rather sort myself rather than pay garage prices are there any readings i can do with forscan/elm config to see if it indicates the problem injector/injectors 

[Tdci-Peter]

3 hours ago, Dennis the meance said:

dreaded Siemens dodgy injectors

From what I have read about the 2008 VDO Injector problem, injector related error codes start to appear, after hesitations at speed and under power. (Siemens sold the VDO injector business to Continental (who also make tyres) in 2007, co-incidentally just before the injector crisis!)

So keep monitoring for codes using a good system like Forscan.

Cylinder balance may help, though on my car it looked suspiciously unreal (all the same reading), also fuel rail pressure (FRP) and VCV signal (VCV indicates the amount of fuel being returned to the tank, low VCV signal means high injector leak-off.)

But without a reference to compare, you can only really look for changes. I have done a couple of Forscan log runs on my car, but the signals are so dynamic (with driving conditions), that comparison would be hard. Sudden unexpected dips in FRP or in VCV could show an intermittent problem though.

One owner (on this site) did cure the injector problem for a couple of hundred quid using second hand parts and own labour, but I suspect he was both lucky and skilled!

I can post more info on my Forscan logs if you need.

 

[Phil21185]

Are you sure it's the injectors? Fuel filter can cause similar problems if it's due for a change. Could really do to know if any codes are stored.

[frozenwhitdave]

hi,its my first focus,and i have noticed the same problem,same veicle.i know the fuel filter and air are new.Would injector cleaner that u put the tank,sort this problem?

 

[Meercat]

never been a fan of in the tank fix all problems additives' having said that my Sons 1.8 tdci suffered a similar problem even after changing fuel filter 

problem was on his car was the inlet manifold pipe from the intercooler was virtually choked with oily crud, we cleaned all pipes up to the egr valve which was also coked up

[FatHead1979]

+1 for the fuel filter.  My MK2 Focus 1.8 TDCi does about 12K a year and I service it every summer but had started to get a bit sluggish recently.  Today, a £6 Bosch fuel filter later and she flies again, I'm always amazed how critical the fuel filter is on modern common rail diesels and also how crappy the filters look after just 6 months.  (I lobbed it in the bin but probably should have took a photo).

IMHO if anyone with a TDCi is experiencing lumpy running/sluggish pick up on light throttle etc other than cleaning the 2 easy to reach sensors and making sure the air filter is crapped up, also swapping out the fuel filter is a cheap step that won't hurt things and might just fix the issue.

[Tdci-Peter]

23 hours ago, frozenwhitdave said:

same problem,same vehicle.i know the fuel filter and air are new.

A very possible link between fuel filter and hesitations or jerking, especially with no error codes, is air getting into the system. The system up to the main pump is under suction, including the filter housing. Even a tiny bit of air getting in will, as it goes through the system, cause fuel rail pressure dips, and hence power dips.

If the filter is getting clogged, that increases suction, making leaks worse.

But if the filter has just been changed, it is more likely the housing has not fully re-sealed, and is letting air in. Try replacing the sealing ring, checking for any damage to the housing, and re-tightening the filter housing. You will need to re-prime after this to start the car.

 

[Dennis the meance]

thanks for all the pointers ive no codes stored when i scanned it it is due a service ill service in next couple weeks and see if it helps or cures it 

tdci-Peter ive run forscan monitoring cylinder balance and number 2 and 4 are same reading  number 1,4 are a higher reading

2,4 are 0.890 at idle 1 is 1.1 and 4 is 1.209 

[Tdci-Peter]

4 hours ago, Dennis the meance said:

ive run forscan monitoring cylinder balance and number 2 and 4 are same reading  number 1,4 are a higher reading

2,4 are 0.890 at idle 1 is 1.1 and 4 is 1.209 

As I hinted at in my post above, I do not know for sure what "cylinder balance" is actually based on, so can not say for certain what it means!

It could be from tiny speed fluctuations in the crank sensor, that indicate different torque and hence pressure variations from cylinder to cylinder. Older 1.8TDCIs have a knock sensor, which can detect the sound, or pressure wave, from each combustion, but I am fairly sure the later ones (post about 2008) do not have this. There is no exhaust gas composition, flow, pressure or temperature monitoring at all on a 1.8TDCI, so it almost has to be the crank sensor.

Anyway, 0.9 to 1.2 sounds like quite a large variation to me. I would be (pleasantly!) surprised if filter or oil changes altered this much. If the diagnostics are correct, then either lower compression on one or two cylinders, or an injector running below par would be the likely causes.

However, the diagnostics are not the final answer. I admit I could be accused of always banging on about diagnostics, first thing I say when I hear anyone complain of a problem, or a warning light on, is get some diagnostics, preferably Forscan! But I also say these diagnostics are flawed, they are only as good as the programmer who "writ the cod" that is behind them, and the sensor systems that Ford condescended to fit. Real life symptoms, and old fashioned tests of what is actually happening are more important. Diagnostics are clues that point to a general area, not always to a specific failure point. I have seen and experienced a few examples of this.

I think it is best to eliminate the basic faults like air entering the fuel system or clogged filters first, and see how it goes.