Ok, so if there is no code I assume the flap is working. I am thinking its possible that the injectors may be struggling to provide the cold start lean burn fuel quantity. Since mine have 141K miles, maybe the next step is to have them serviced and balanced. What is the service life/Maintenance interval for DGI injectors?
I can't remember if the code will set the engine light on on the dash. A simple scanner may not pick it up as it will vw specific.
I don't remember seeing service interval specified for the injectors. I would pull the plugs and compare and see if the top of the piston is wet or has any fuel sat on top . This would be a good indicator of an injector problem
Also compare the plugs , look for colur changes and gap across the plugs . A cheap option to check first
I have a borescope and I know the valves seat well because I just did the decarbonization and used a soak/scrape/ziptie method. They are super-clean now and the P300 series code comes up still. I have pulled plugs and they read normal and all the same, but I can check it again. My code scanner is a VW/Audi specific one so I assume it will read out the actuator and I have not seen that code at all. Injector forums suggest the possibility that the injectors are "slow" and could be struggling to pulse fast enough at cold idle to provide fuel properly. Having them serviced isn't really expensive, it just takes time to pull them out and ship them back and forth to the shop. I am told the stock VW injectors come with plastic inlet screens that degrade over time and could partially clog the injector. These are LONG-SHOTS but I do not hear many other options.
This is a really challenging issue and still looking for a solution.
I have seen posts re injectors breaking down . But not seen any real evidence . It seems your a bit stuck as the only other option I can think of is to swap the injectors around to see if the fault moves to another cylinder. But that's a lot of work and injectors will needed to be cleaned and resealed.
Any evidence of leaking injectors ie fuel in cylinder?
No evidence of leaking injector but I do feel the car should get better fuel mileage than it does (25mpg) but its not bad. I think I will check for vacuum leaks again, drive it for a while and see if I get any consistent code. For a while it was always P303 (cylinder 3) but now I get the random one P300 and sometimes P301, so maybe I can narrow it down. I'l drive for a while and get back to this post if I have a conclusion.
I never had a DGI injector fail on me, but Port Injectors I have had fail all the time, mostly leakers and once a really slow one that appeared to be clogged. oh, and some port injectors I have bought supposedly new were total china-junk. Never again.
Just re reading this post. I also have a misfire on cylinder 3 at idle. Not enough to set a code , but can be seen on the misfire counter .
I've also tried new coils and plugs with new noticeable difference. Also no sign of a leak or vacuum problems.
I have tried to inject a cleaner via the throttle body and no difference. I have used good quality fuel injector cleaners that have a high % of PEA addative in them for a few years now and it has made a slight improvement.
Also replaced the front and rear pcv and evap valve and vacuum lines , with no improvement. The above was done to sort other problems but can also relate to misfire issues.
I have read a few posts and people just end up living with it if there are no drivability issues . My car just passed its MOT with no emissions problems.
I did also check the fuel pressure, see vcds YouTube video, to see if I was dropping pressure after the car as left for a few days . But all OK on that font . Compression test OK as well.
In summary I'm in the same position, tied the same things , but still have slight mis on cylinder 3 . You can just about feel it at idle but only just .
It seems to be more noticeable if the car is pointing slightly up at the front when at a junction , but only just . I was thinking that the flaps are returning to the correct position at idle due to carbon build up / slightly sticking but not enough to set a code .
Did you clean the inlet manifold / flaps when you did the valves? Did you have much crud ?
I've not removed the inlet manifold to clean the valves as a few posts suggest this make no difference...
I also notice the miss more often when facing uphill, but again its very minor. The flaps in the head were carbon coated but I cleaned them shiny. The flaps in the intake were not bad at all, slightly oily from PCV but I just wiped them off with some cleaner. The pressure loss test appears to see if an injector is leaking, so again, I am back to the injector possibility. I am thinking I might explore the flap position possibility before pulling injectors. I may film the cold start positions of the lever that actuates them and see if they move full travel and quickly. I am sure the actuator does not last forever. Other people have suggested replacing the entire manifold and flap system, but I am not sure how that would help.
There are 2 ways to design motorised flaps, I only worked on my diesel TDi but V.W probably follow the same principles for their gas engines? If the flap motor assembly has more than 2 wires then it is most likely to have flap position sensing feedback involving more electronics. V.W tend to use simpler dc 2 wire flap motors and pulse them to reach positions from fully open to fully closed. When you first turn on ignition the flaps get calibrated and with a flap visible you should be able to see this happening? At ignition on the flap is pulsed to fully open where its motor stall current is sensed, then it is pulsed to fully closed and the number of pulses between fully open and closed is counted. The flap controller then pulses the flap X pulses + or - to set intermediate positions. With this system, diagnostics can't tell you the physical position of the flap, only the number of pulses the motor got to set it to a position it is expected to be.
Lets's say the flap was sticking with carbon near the fully closed position? At key on the fully closed flap starting position would be wrong. The system knows approximately how many pulses correspond to a flap moving from fully closed to open and normally a diagnostic fault would be set soon after key on. If ignition on calibration was ok and the flap was sticking after key on, the flap positions would all be wrong and diagnostics would show nothing.
Now back to misfiring because there are a lot of inputs posted and you need to take a pedantic methodical approach. I'm on diesel but I'll share what I've done in the past. Diagnostics may report problems with cylinder 2 but are you sure? Misfires are normally diagnosed from an anti knock sensor or the camshaft position sensor, there is no diagnostic link to the spark generation or injector firing. It can tell you a spark pulse was initiated, but not if it came out at the plug!
The first thing to do is remove a plug on one of the 'good' cylinders and check diagnostics puts up a fault code on that cylinder. Nobody seems to want to swap parts around to provide further evidence? Once diagnostics confirms your bad cylinder, you swap over the plug/coil/ injector to see if the misfire fault moves. If it doesn't you are left with the ECU and physical parts like air control or fuelling.
All gas engines require fuel, air in correct proportion and an ignition spark at the right time. At idle the air volume required is very small and metering by flap valves requires high accuracy. If you are old enough to have worked on carb. motors, you will know that worn butterfly spindles allowing air to bypass the butterfly frequently cause idle problems. An electronic flap valve is no different. The easiest variable for me to eliminate is the 'spark at the right time' or missing sparks. I would go no further wasting effort until I was convinced the ignition sequence wasn't missing sparks.
I'm lucky I've got a storage 'scope and some Pico tools but there's something simple you can try to confirm the spark sequence isn't missing sparks: Get yourself a Xenon timing light and attach the pickup sensing wire around the suspect plug HT coil (not the input wire!). Make a bold white mark on the crankshaft pulley and idle the motor whilst it's misfiring. If ignition is repetitive and not missing sparks the white timing mark will remain stable and visible each flash. If the mark disappears (no strobe flash) or appears to flash randomly out of sequence, then you confirm that one or more firing pulses were missing. Forget all the other things because you are looking for an electronic ignition firing fault. The ECU, ground wiring to coils, the crankshaft position sensor (there's usually 2, one for each cylinder pair) could be things to look at although CPS is more likely to show a problem at high rpm.
If you want to play around with the flap valves with the manifold removed, you should be able to turn on the ignition and watch them go through their calibration sequence if they work they way I explained. Have Fun!
I have already swapped parts around, It does NOT follow the ignition parts. I could swap injectors around, but by the time I get the injectors out I might as well service them (its a big job).
I do suspect the flaps, but unlike a carb butterfly valve, I cannot easily check it for play. When I had the manifold out I verified it moved and it did not seem overly loose or super-dirty.
Your explanation of how the actuator works made me think of a another thing. Maybe its intermittent and the "calibration" it did does not quite cover it. I can change out this actuator for about $60 to $100, so maybe I will try that if during my video I do not see it move properly. Worth considering so thanks for the idea.
You haven't proved conclusively there is random loss of ignition because the ECU,wiring and crank sensors are still the same parts to the faulting cylinder.
That photo shows a more complex assembly than my TVA flap valve. Does the wiring diagram part diagram reveal anything like vacuum sensors inside?You will know that carb butterflies are poor in their near closed position and require additional jets to get smooth idle.
Your photo shows cylindrical profiles on the casting of the type that might retain fine air metering jets? Have you tried to work out how it works before buying a replacement?
While I will agree with your statement, the probability of ignition is low. Here is why:
ECU problem: The symptom is only throwing codes at cold start and cold run, not at high rpm or any other mode that would stress the MOSFETs in the ECU to drive the coils. While it is possible its the ECU, there would be many other symptoms in all driving modes, so that is eliminated due to statistical likelihood.
Wiring problem: wiring is only 4 possibilities: short, open, intermittent short or intermittent connection. If any of these occurred there would be additional codes and I would expect it would run bad in all modes and RPM's which, as noted the symptoms do not align. Any wiring issue I would expect to be almost catastrophic to drivability.
Crank sensor: Similar to wiring problem it would provide many more symptoms and at all RPM's which is not the case.
I would guess from the photo that its pretty simple device. (next time I hit the junkyard I'll crack one open) There are no vacuum connections, just an electrical connector and the lever it moves. So basically the cylinder on the right is a motor, the large circular area appears to be a gear to step up the torque. I would expect there to be two microswitches internal that activate when it reaches fully open and fully closed. That is about it. I am pretty sure that is all it does so its a pretty "dumb" device. Someone here may be able to confirm.
I do have an idea. So when you are normally driving the car hot the actuator is fully open (homogeneous mode). When the car is cold this actuator sits at the fully open position until you put the key into the ignition and turn it on. Then it actuates moving the flap to the stratify position. This normally takes how long? Should it be fast like 1 second? I think mine takes almost 5 seconds to shift the position, which seems very long. If I jump in the cold car and turn the key all the way from off to crank, it appears more likely to throw a code than if I turn the key on, wait 5 seconds and then crank. I believe I may be on the track to the problem. I believe the cold start actuator does not get into position fast enough before cranking causing multiple misfires until it gets in the stratify position. I will investigate this via video and empirical trials.
There's more than one poster in this thread with a misfire problem and a solution for one isn't necessarily a solution for all. A misfire can be on one, 2 or all cylinders and the faults could be different. I suggested you had to eliminate these first with simple swaps before removing and replacing parts without confirmation they were actually faulty.
You can't eliminate the ECU for some misfire faults. When the ECU mosfets are driving the ignition coils at higher rpm, misfiring can be caused by lack of speed and one culprit is when people put in aftermarket coil packs. The ECU coil triggering at high rpm is matched to coil pack inductance and resistance to get the fastest and most reliable spark triggering. OEM coils are designed for consistent operation matched to the ECU mosfet drivers. Chinese equivalents and so called booster coil packs may not be.
Testing for sync between fuel injection and ignition timing is a bit harder to do but eliminates important variables, leaving air mixture as a possible fault to follow. Since it's an Efi engine, the flap valve is in a loop with control inputs coming from other parts of the system - e.g MAF and temperature sensors.
The way to check and eliminate any misfiring due to missing injection or ignition timing pulses is to use a 20mHz dual channel USB storage scope on a laptop. You put the injector pulses on A channel and use the B channel to monitor HV spikes from the coil pack. Run the motor at idle when the fault is ocurring whilst capturing the pulses. There should be no timing gaps and an ignition pulse always occurs after an injection pulse. On these engines there are TWO injection pulses and one ignition firing pulse per cycle. Play back the captured sequence and check the injector is always fired twice later, again with no time gaps compared to the previous pulse triple
Maybe you aren't up for this and you will just go straight to replacing the flap valve assembly? When you talk about the stratify position I doubt it will be one position, but a variable position determined by other sensors, e.g the ECU fuelling map, temperature sensors and DI fuel pump injection pressure control? When V.W design these closed loop Efi feedback control systems, they often build in preset limits to ensure the engine will keep running of sorts, even if there's a control loop problem or a critical sensor is working outside its expected range. If I saw the flap valve moving to different positions as sensors warmed up I'd think the feedback loop was in control. If the flap stayed in the same place each time at cold key on, even after fooling a temperature sensor, I'd think the control loop wasn't working?
You can follow the attached links which explain how extra fuel is injected twice and on the compression stroke just before ignition. This will be the highest compression point where the DI fuel pump must produce a greater pressure. This suggests these injectors may be a special design? I assume all these important parts are genuine OE and not substitutes? You said it would be hard to swap an injector so it still remains an uncertain item? On my Tdi I unlock each injector fuel union, fiddle them out around the steel fuel lines or remove the lines for better access, then bleed fuel through after replacing.
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Just seen another post on a similar topic and the suggestion was to check cylinder 3 Cam lobe . An easy check if your remove the rocker cover .might need a new gasket mind . You can remove the plugs and turn the engine over by hand and compare to other cylinders . A bit out there as a check but it's easy and cheap. The findings on the other site was that some visible wear on Cam lobe 3 was affecting the valve movement , but it was only on cold start / idle
Vox: I need a shade-tree mechanic solution. While I would love to hook up a scope that would be outside the available tools I have and I am not willing to pay a dealership for this service. As I said I will be studying the actuator and valve via video and testing. After that, I will probably just have the injectors removed and serviced since they have 140K miles on them.
Rob: That might be worth checking and pretty easy. Thanks. I get P303 consistently, but also get the random one (P300) and sometimes cylinder 1, so I think it might systemic and not a single cylinder. I can probably just measure them all when I get in there.
Valve timing. That's an interesting one because diagnostics tells you timings but that's from the camshaft sensor which is meaningless if a cam lobe profile is worn. If you're getting injectors refurbed, why not swap 2 first? What kind of refurb? I've had them done for diesels and they tend to replace the complete nozzle tip and pintle (Bosch).
Just watched a video on YouTube from pine hallow auto diagnostics. I think you can make out the title from the attached pic . It shows how to test for injector vs spark problems, as per Vox's suggestion. It does need a scope mind and not sure how accessible the injector wires are with the inlet still in place but it shows the process / diagnostic approach.
What scope are you using as was looking into getting one ?
I'm not home so will have to check. It's a chinese sourced usb clone of something else with software. It will also capture and decode Can data stream! There are plenty of multichannel types but only good for logic work. Mine is 2 channel analogue inputs 0 to 5volt a_d. 20Mhz for fast pulses.
You learn tricks for using other non-plug and play diagnostics tools. With most VW connectors you can push ceramic balled mapping pins in the end of a connector or through a pvc wire warmed up with a hair dryer. I use my usb scope on a battery powered laptop, that way its totally isolated from the car. An accurate wiring diagram with matching wire colors is essential if you can't easily get to a connector. The ECU connector in the plenum is a good place to be because many parts are driven from there. I don't need a YT video as I've done plenty of work in test & measurement.
If you look at Pico automotive tools, they understand what other diagnostic tools may be needed. I have a pair of their battery operated Hi Z probes. Used with normal mains scopes they allow totally isolated measurements, including high voltage switchmode power supplies. Once you run out of answers from built in diagnostics you need to become a fault finding engineer or pay a dealer who has access to thousands of similar faults to help them.
Automotive diagnostic products from Pico Technology. PicoScope oscilloscopes (labscopes), NVH kits, pressure sensors, current clamps and accessories
IMHO the dealer solution will always be 'old for new' expensive parts replacement. If you take the trouble to learn how things should work and have test experience, you can often repair the non-working part. But car Efi systems with control feedback can be quite hard to work on. I've had some tricky faults in the past where I've had to disconnect a feedback sensor and replace it with a variable resistor or a voltage source. I consider myself a shade tree mechanic, but I understand when conventional knowlege and the internet won't solve every problem.
Even V.W dealers may not have a solution, because they work to pre-designed fault finding algorithms just like a diagnostics app, whereas engineers can work outside the box, take nothing for granted and develop their own fault finding strategy.