Tame Technician can you help please?
Discussion
Hi TT
My garage is troubleshooting my A4 2.0 tdi 140 avant 80K
there is a slight pulsing sensation at about 1800 RPM, especially in higher gears under load.
the MAF is new, the EGR is new (basic setting applied), it has fully serviced with cambelt & waterpump and 4 new glow plugs. apart from this weirdness, it goes well. They are telling me it is the wiring loom under the rocker cover for the injectors and glow plugs? £200 fitted.
is this likely ??? sounds a bit of a stab in the dark to me?
Thanks in advance
Cindacone
My garage is troubleshooting my A4 2.0 tdi 140 avant 80K
there is a slight pulsing sensation at about 1800 RPM, especially in higher gears under load.
the MAF is new, the EGR is new (basic setting applied), it has fully serviced with cambelt & waterpump and 4 new glow plugs. apart from this weirdness, it goes well. They are telling me it is the wiring loom under the rocker cover for the injectors and glow plugs? £200 fitted.
is this likely ??? sounds a bit of a stab in the dark to me?
Thanks in advance
Cindacone
As ever to try to diagnose it propperly need more input.
Have they driven the car and felt the problem how bad is it, how is it on full throtle at high rpm. If its fine else where in the rev range, I doubt it will be that harness.
Has it logged any fault codes??
What makes them think it the harness,
Why did it have glow plugs?
Why did it have an EGR valve?
Did these items fix anything?
I'm guessing there was a fault code saying one of the glow plugs was faulty so they replaced all 4 of them?? and with new ones its still logging the fault on only one of them. If this the case, the harness is the likely cause of the fault being logged, but I still dont think thats the cause of teh surging.
I've only ever replaced that harness on the 170bhp 2.0TDI's where if an injector fails you have to replace the harness to, as per workshop manual. Not the case on the 140bhp engines.
I've never changed that harness on a 140BHP engine.
What do they think about the rough idle??
sry so many Q's but it helps me find out what going on with the car.
Have they driven the car and felt the problem how bad is it, how is it on full throtle at high rpm. If its fine else where in the rev range, I doubt it will be that harness.
Has it logged any fault codes??
What makes them think it the harness,
Why did it have glow plugs?
Why did it have an EGR valve?
Did these items fix anything?
I'm guessing there was a fault code saying one of the glow plugs was faulty so they replaced all 4 of them?? and with new ones its still logging the fault on only one of them. If this the case, the harness is the likely cause of the fault being logged, but I still dont think thats the cause of teh surging.
I've only ever replaced that harness on the 170bhp 2.0TDI's where if an injector fails you have to replace the harness to, as per workshop manual. Not the case on the 140bhp engines.
I've never changed that harness on a 140BHP engine.
What do they think about the rough idle??
sry so many Q's but it helps me find out what going on with the car.
Hi
they drove it and diagnosed on VAGCOM etc. it seems ok apart from the 1800rpm pulsing. the fault codes they say have been cleared by a new EGR and plugs. Only one plug was faulty but they said best to replace all whilst rocker cover off. the emission light has gone away, so must trust them that it needed these bits.
It was a firm with an apparently good rep - Awesoume GTi - Lymn
They think wiring loom because they say they have seen it many times on the 1.9TDi and I think they are grasping at straws! they told me it was maf, when i told them the maf was new, they changed to the wiring loom. Apparently it corodes, but surely this would cause issues through all revs??
they think the rough idle as it should be - just a "feature" of the pd engine.
Thanks TT
they drove it and diagnosed on VAGCOM etc. it seems ok apart from the 1800rpm pulsing. the fault codes they say have been cleared by a new EGR and plugs. Only one plug was faulty but they said best to replace all whilst rocker cover off. the emission light has gone away, so must trust them that it needed these bits.
It was a firm with an apparently good rep - Awesoume GTi - Lymn
They think wiring loom because they say they have seen it many times on the 1.9TDi and I think they are grasping at straws! they told me it was maf, when i told them the maf was new, they changed to the wiring loom. Apparently it corodes, but surely this would cause issues through all revs??
they think the rough idle as it should be - just a "feature" of the pd engine.
Thanks TT
hi there just wanted to shed some light on this for you we have come across this problem before and we to have replaced the small loom inside the head under the rocker cover on many vw and audis this loom is very short and it controls the fuel injectors, it seems that where the loom is sat in the head it gets very hot and the wires become brital the alows oil to get in the wire and reduce the signal, some times it will put a fault code in the system with one of the cylinders but not always if its just started to play up.
its an easy job to do bit fidly but they don't have to remove the cylinder head just the rocker cover you can do a resistance check down the wire but it don't always show if the wire isn't fully broken.
its an easy job to do bit fidly but they don't have to remove the cylinder head just the rocker cover you can do a resistance check down the wire but it don't always show if the wire isn't fully broken.
its worth while changing it if your having a running fault and you've done every thing else i've seen people replace the injectors when its been the loom faulty,
it is a job you could probably do on your own but you have to be forcefull at getting the loom out and in req a bit of bending of the plastic runner its attacted to, it the only way really to do it with out removing the cylinder head.
prob be worth while changing the rocker cover gasket to while its off.
it is a job you could probably do on your own but you have to be forcefull at getting the loom out and in req a bit of bending of the plastic runner its attacted to, it the only way really to do it with out removing the cylinder head.
prob be worth while changing the rocker cover gasket to while its off.
2.0 TDI Rough idle checks
(1) Fuel quality, take the hose off the filter have some one turn the ign off and on 2 or 3 time and chatch some fuel in a clear glass container, milk bottle/jam jar.
Look at it is it black, or at least darker than it should be.
Engine oil can get in the fuel (two failure cause this) and sticks to the side of the tank, so even when the causes have been fixed the problem can continue.
Oil in the fuel is either caused by a defective tandem pump, or leaking injector seals. You will usually know when you have either problem as there is a misfire at high rpm on full throtle. But if these fault have occured in the past and been repaired or not got to that level yet, you can still end up with oil in the tank and no high rpm misfire.
If the fuel is totally black you need to fix the cause (pump or seals) if its just a bit dark advise remove the fuel pump/sender unit and get in there and clean the inside of the tank by hand, it will be black and oily.
Diesel fuel should be a slightly yellow colour in the light. Although it can look almost blue/green in the dark (no idea why)
(2) Injector condition, we have had good results removing and ultra-sonically cleaning the PD injectors. Improves the idle roughness and gives a litle top end performance increase. To be sure if they need doing you need to road test monitoring the lambda value, lambda on full throtle at high rpm, after a good few runs to clear it out, should be less than 1.37, typically its about 1.58 ish before the clean and 1.2 ish after.
Boost leaks and MAF faults can cause funny lambda reading, typically a MAF fault would give very high lambda readings (4 or 5) at high rpm.
If the injectors are coming out, you must replace the seals as a matter of course.
(3) I know i can adjust the idle speed slighty with 5051, I asume there fore it can be done with VAGCOM. 900 is ok, but it should be 800ish. Normally turning it up make the idle better so turning it down might make it worse.
Be aware 2.0TDI's all have a slightly rough idle, you will be very lucky to get rid of it completely. But the clean injectors and a fuel tank with no oil in usually give a dramatic improvement.
(1) Fuel quality, take the hose off the filter have some one turn the ign off and on 2 or 3 time and chatch some fuel in a clear glass container, milk bottle/jam jar.
Look at it is it black, or at least darker than it should be.
Engine oil can get in the fuel (two failure cause this) and sticks to the side of the tank, so even when the causes have been fixed the problem can continue.
Oil in the fuel is either caused by a defective tandem pump, or leaking injector seals. You will usually know when you have either problem as there is a misfire at high rpm on full throtle. But if these fault have occured in the past and been repaired or not got to that level yet, you can still end up with oil in the tank and no high rpm misfire.
If the fuel is totally black you need to fix the cause (pump or seals) if its just a bit dark advise remove the fuel pump/sender unit and get in there and clean the inside of the tank by hand, it will be black and oily.
Diesel fuel should be a slightly yellow colour in the light. Although it can look almost blue/green in the dark (no idea why)
(2) Injector condition, we have had good results removing and ultra-sonically cleaning the PD injectors. Improves the idle roughness and gives a litle top end performance increase. To be sure if they need doing you need to road test monitoring the lambda value, lambda on full throtle at high rpm, after a good few runs to clear it out, should be less than 1.37, typically its about 1.58 ish before the clean and 1.2 ish after.
Boost leaks and MAF faults can cause funny lambda reading, typically a MAF fault would give very high lambda readings (4 or 5) at high rpm.
If the injectors are coming out, you must replace the seals as a matter of course.
(3) I know i can adjust the idle speed slighty with 5051, I asume there fore it can be done with VAGCOM. 900 is ok, but it should be 800ish. Normally turning it up make the idle better so turning it down might make it worse.
Be aware 2.0TDI's all have a slightly rough idle, you will be very lucky to get rid of it completely. But the clean injectors and a fuel tank with no oil in usually give a dramatic improvement.
I'm not being funny, but if you cant see how to get the rocker cover off, just by looking at it, I dont like your chances of changing the harness.
I had a google and cant find any guide, I could write a load of text but without the pics would prbably make no sence.
I had a google and cant find any guide, I could write a load of text but without the pics would prbably make no sence.
Edited by Tame Technician on Sunday 29th November 16:22
To clean the injectors they have to be removed from the engine and put in an ultra sonic cleaner for 90mins, so its a rocker cover, rocker shaft remval job.
There is a proper Audi tool to do it presumably injection specialists (diesel) will be able to do the same. Yellow pages, google etc.
I think if you use quality fuel like that, from new, all the time, engines do bennefit very slightly. One tank full now and then does nothing. And in my experience anything you can buy in a tin, makes no difference to engines at all.
Check the colour of the fuel first.
There is a proper Audi tool to do it presumably injection specialists (diesel) will be able to do the same. Yellow pages, google etc.
I think if you use quality fuel like that, from new, all the time, engines do bennefit very slightly. One tank full now and then does nothing. And in my experience anything you can buy in a tin, makes no difference to engines at all.
Check the colour of the fuel first.
yeah as tame tech has mentioned above they can get sooted up or have problems if oil has found its way back into the tank, have not come across to many problems with the pressure pump on the side of the cylinder head but have seen them play up before, also worth making sure the engine is using the correct oil as this can cause problems with the injectors.
Edited by skid-mark on Wednesday 2nd December 19:54
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