A4 1.9tdi AVF engine woes

[ThunderWolf78]

So, a short presentation might be due first:
I have an Avant 1.9TDI 2002 with AVF PD engine, 6spd manual, ut has so far run 333203kms.

A short while ago I noticed that engine vibrations hade risen above my "this is okay and comfortable" - threshold, I have stiffer mounts around (except front buffer which is a new oem buffer) and idle vibrations increased a bit as expected when I had done the swap. The flywheel is new(and already diagnosed to be ok), the driveshafts are free from play and the boots are ok(which wouldn't matter anyway since the vibrations are there at standstill too and follow the rpm of the engine).

I don't have any errors pertaining to the injectors when I check codes, I do have the code referring to left motor mount broken circuit(since it's not there). I have however run the car for a short trip today using the flight recorder of my autocom adapter, I recorded fuel amounts, corrections, engine rpms and just about everything I could tick off in the list of stuff to monitor. Injectors #1 and #4 deviate more than #2 and #3 and I am going to swap the wiring loom tomorrow evening and also check up on camshaft and lifter wear to see if a new camshaft is needed anytime soon.

However, I thought I'd check how much blow-by the engine was creating and loosened the oil filler cap and had it sitting on the valve cover with engine running, it "chatters" around a bit but doesn't fall off(I also had a friend come over with his Passat, same engine, "merely" 278050kms, same gearbox and his does exactly the same apart from the rough running of mine), my car pulls fine, starts without a hiccup regardless of temperature, doesn't smoke except for a miniscule puff of black at start once in a while, never under acceleration or engine braking.

While I was rummaging around the general area I thought about vacuum leaks, I replaced all vacuum lines a year ago as most of them were rubbish, but now I noticed that the connection nipple(or vacuum inlet/outlet) on the tandempump could "wiggle", I suspect that this is not intended and thus creates a leak(brakes are fine so it cant be horrible). The question now is how this nipple is supposed to be attached to the pump body, pressed in or screwed? Since it's being subjected to vacuum I could probably just glue it in with something and the suction would make sure it seals good while running but I like to repair things properly and am not fond of swapoing out parts that can be repaired, my budget for keeping the car in good shape isn't that huge.

The exhaust fumes sting your eyes a tad, like all fuel wasn't perfectly combusted, could this be because of two injectors not playing along as happily as the other two? This has developed about the same time as the vibration increased, before this they just smelled as awful as pseudo modern diesel engine exhaust smells(compared to the quite aromatic smell of the exhaust on my father's 1964 pre-chamber diesel engine of his Fordson Super Dexta).

It doesn't consume water, it doesn't mix water and oil and there are no compression in the coolant system, I've only once had to top up engine oil with a whopping 200ml between oil changes(which I do myself every 10000-12000kms), am running 5W40 VAG 505.1 spec oil, oil pressure hovers around 1.6bar at idle with warm engine and usually around 3.something at 2000ish rpm.

Ideas and suggestions welcome as this is annoying me and it's not supposed to do this.

[ThunderWolf78]

Everybody just loves feedback(But I've seen in other threads that once the problem is fixed people magically forget to enter their feedback), I've visually inspected the innards that are visible through lifting the valve cover, swapped out my injector loom(done in a pinch even though space is slim), the lobes on the camshaft look... New... It's ever so slightly begun taking maybe .05 or so off the tips(the chamfered edge is intact) , no scoring or beating up of the lifters, the injector rockers look plenty fine too. I've found out that the vacuum outlet/inlet on the pump is swaged into(I figured this out by breaking it off) the pump, inside sat some sorry excuse for beaten up and abused seal, now I just gotta figure out how to secure the connection on the pump again.

Anyways, I think I'll be inspecting that flywheel shortly if tonight's fiddling doesn't solve the problem.

[diagnosticator]

I don't believe the new flywheel is involved with the excess idle vibration. I am sure the stiffer engine mounts are involved, being less compliant than the OEM mounts. Also, one or both original equipment engine mounts on the TDI is/are electrically controlled, and are calibrated to be very soft and compliant at idle, then the ECU shifts a solenoid damping valve inside the mount causing the mount to stiffen up a lot while the car is being driven with the engine running above idle speed. If you installed aftermarket non electrically controlled engine mount/s, the mount/s will be to stiff at idle speed, resulting in a lot higher vibration levels in the cabin.

The injectors that are delivering different amount of fuel per injection pump stroke, will definitely provoke rough running at idle speed, being a lot less noticeable at higher RPMs. The fuel mass delivered per pump stroke error from two injectors could be caused by worn injector nozzles, incorrect nozzle opening pressure or the fuel injection pump delivery is not even on all cylinders.

You can have the situation evaluated by a good diesel fuel injection specialist shop. The shop will test the injectors on a test bench measuring the fuel delivery mass/volume for each injector, and the nozzle popping (opening) pressure and nozzle spray pattern. All the injectors must open at the same pressure value +/- the allowed tolerance of variation across the set. The spray pattern from the nozzles must be correct with the specified spray pattern and with proper dispersion of the fuel spray droplets. The injectors must open and close cleanly without any fuel dribble or leaking between fuel injections.

The injector nozzle tips have a limited useful lifetime. With the mileage/Kms you have on your A4 TDI, if the injectors are original equipment they are certainly overdue for new nozzle tips and readjustment of the injector nozzle opening pressure setting. The fuel injection pump is somewhat more durable, but it also suffers wear and must be rebuilt eventually. Your injection pump needs to be run on the pump test stand to determine if it needs to be rebuilt now, or if it can be used as is for awhile longer.

The correct function of the injectors is crucial for optimum running qualities, smooth performance and best fuel economy, however the fuel injection pump is the real heart and brains of your TDI, and must be working first rate in order for the engine to run as well as it is capable of.

The diesel fuel injection specialist shop can provide a new hose nipple for fitting to the injection pump housing.

Usually, the fuel injectors and the fuel injection pump are removed from the engine by your local Audi service center or independant Audi specialist shop, and the injectors and pump are sent to the diesel fuel injection specialist for evaluation of the wear condition and performance of any required repairs or rebuild work. Then the injectors and injection pump are returned to your regular Aud repair shop and the injectors and injection pump are reinstalled on your engine including replacing the injection pump and camshaft timing drive belt and associated belt tensioner assembly and belt guide pulleys.

The fuel injection pump must be carefully and accurately reinstalled adjusting the injection pump timing to the precise setting specified. A new fuel filter and air filter should be installed as well. Finally, the glow plugs must be checked for proper function and any faulty glow plugs replaced. Any problems with the equipment discussed above can be causing excessive idle vibration in isolation or all together contributing more or less to the sum total excess vibration you are experiencing.

After addressing the several items described above likely causing the high idle vibration, your A4 TDI should be running like new again.

One more item to consider, the fuel injection pump timing advance/ retard setting effects the combustion process in the cylinders. You can request that the injection pump timing is set to the maximum advanced timing setting allowed by the specification value. Advanced injection timing will eliminate most of the eye stinging smell from the exhaust, improve cold starts with reduced or no smoking, and increase engine torque as measured by the average butt dyno, and improve fuel economy. The only drawback with advanced injection timing, is slightly increased combustion rattle noise at idle speed. If it is to noisy for you the idle rattle can be reduced and still enjoy most of the improvements by having your repair shop retard the injection pump timing about 2 degrees from the maximum allowed advanced pump timing setting. Alternatively, you can continue driving your TDI with the maximum advanced injection pump timing and add a fuel cetane improver additive to reduce idle noise, improve cold starting and reduce smell and any smoking adding to the benefits that advanced injection pump timing provides. A quality cetane improver additive will lower the winter fuel gelling temperature point a lot as well, with a very small increase of refueling expenses depending on how much cetane improver additive you use per tank refill.

EDIT: I just noticed your TDI is a PD unit pump injector, this eliminates the fuel injection pump from your equipment list above, since the injection pump function is incorporated with the fuel injectors.

[ThunderWolf78]

Hello J.

Well, the engine mounts are not probably the cause here since they only contributed slightly more vibrations a year ago when I installed them, I am fine with that and I knew beforehand that they would increase the vibrations at idle(I also knew that the left engine mount was electro-hydraulic).

I swapped out the PD injector harness and no longer suffer any excess vibrations at idle.

However... I now have vibrations in between 1800 and 2000 rpm, peaking at 1900rpm, below or above that hardly any vibrations at all. I know that all the other stuff is "due for rebuild" but they will have to wait a little while longer and I plan on rebuilding it when time comes for cam belt swap. I still believe the flywheel is the culprit now and it was only masked by the bad injector harness, hard to differentiate similar vibrations from each other.

I'd also suspect having stiffer exhaust mounts will increase vibrations transferred to the chassis at certain load conditions, this would at the moment be the absolutely easiest thing to check, swap all bushings for softer and then testdrive.

I will ve looking into adjusting the torsion value of my camshaft when I have time(to fix the sting your eyes exhaust fumes), as earlier said, it doesn't smoke, ever, not the slightest hint of white, black or blue smoke unless you turn the key on a cold day without letting the glow symbol turn off first, it's still powerful enough to smoke all manual gearbox BMW's coming off the red-light in this city(They overtake you about 100meters later though)...

Thoughts? /W

[diagnosticator]

Hello J.

Well, the engine mounts are not probably the cause here since they only contributed slightly more vibrations a year ago when I installed them, I am fine with that and I knew beforehand that they would increase the vibrations at idle(I also knew that the left engine mount was electro-hydraulic).

I swapped out the PD injector harness and no longer suffer any excess vibrations at idle.

However... I now have vibrations in between 1800 and 2000 rpm, peaking at 1900rpm, below or above that hardly any vibrations at all. I know that all the other stuff is "due for rebuild" but they will have to wait a little while longer and I plan on rebuilding it when time comes for cam belt swap. I still believe the flywheel is the culprit now and it was only masked by the bad injector harness, hard to differentiate similar vibrations from each other.

I'd also suspect having stiffer exhaust mounts will increase vibrations transferred to the chassis at certain load conditions, this would at the moment be the absolutely easiest thing to check, swap all bushings for softer and then testdrive.

I will ve looking into adjusting the torsion value of my camshaft when I have time(to fix the sting your eyes exhaust fumes), as earlier said, it doesn't smoke, ever, not the slightest hint of white, black or blue smoke unless you turn the key on a cold day without letting the glow symbol turn off first, it's still powerful enough to smoke all manual gearbox BMW's coming off the red-light in this city(They overtake you about 100meters later though)...

Thoughts? /W

I still believe the unit injectors should be tested on the test stand checking for the correct nozzle popping/opening pressure and spray pattern. Especially with direct injection diesels, the spray pattern and popping pressure effects running quality and NVH/engine smoothness a lot, as well as effecting the exhaust odor. With 334,000 kilometers on your TDI, the injector nozzle spray tips have a considerable amount wear existing now. The popping pressure is no doubt off the set point specification as well. In addition, wear in the unit injector pumps will cause variation in the delivered fuel mass per injection stoke per cylinder, with an associated unbalanced per cylinder torque output. An alternative to having the unit pump injectors tested for correct function, with the kilometers on your A4, it is reasonable and justifiable to simply replace the unit pump injectors with re-manufactured exchange parts. The fuel filter should be replaced also.

The correct injection timing specification set point begins fuel injection several crankshaft rotational degrees Before Top Dead Center, with the piston on the compression stroke. If the spray pattern and nozzle opening/popping pressure are off specification, will cause effectively late injection timing and delayed combustion. With the effective injection timing retarded with relation to the crankshaft/ piston position, the effective combustion process will be occurring late, at some unknown point of the piston position After Top Dead Center, on the power stroke . When injection timing/combustion process is delayed/retarded, beginning After Top Dead Center during the power stroke, the exhaust will have a strong irritating odor that stings the eyes and is irritating to the respiratory airway tissues due to incomplete combustion of the heavier fuel fractions of the total fuel mass injected. The unit pump/injector injection timing can only be properly adjusted if the injector nozzle popping/opening pressure is set correctly, and the associated nozzle spray pattern with uniformly atomized fuel spray distribution in the combustion chamber. The unit pump/injector must open and close cleanly and quickly, with no fuel dribble between injection cycles. If the injector nozzle is dribbling between injection cycles, will provoke strong exhaust odor from incomplete fuel combustion with unburned fuel escaping out of the exhaust ports during the exhaust stroke.

[ThunderWolf78]

I can't argue with you about that but it will still have to wait, I changed engine oil yesterday and had a look at my engine mounts, both are sagging so badly that the engine sits almost a centimeter lower than it did when I swapped out the old ones and it was more or less resting on the front bump stop. For now I've shimmed them up and the vibration is nowhere near as bad anymore but I'll have to contact the dealer I bought them from and see if he will replace them under warranty. Injectors will follow sometime next year.