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Discussion Starter #21 (Edited)
I wouldn't expect the colder plugs to make that much of a difference either, but I was doing a constant 5K RPM on the highway for several miles. Perhaps that fouled them out. I don't know.

When I changed the plugs a week ago I also changed the coils. I put in new plugs this morning. It seems to run better, but there is a slight lurching under load. Perhaps this is due to some carbon build up.

I'm not sure what is up with the injectors, but it must be fairly common since VW extended the warranty on these. I just need to find if I have an injector issue and push the dealer to replace. I do not have the skills or tools to switch out the injectors. I will be out of the extended warranty in about 600 miles. My guess is because the injector issue is intermittent, the dealer will not be able to duplicate the issue. Since I am taking it to the dealer on Tuesday, I am toying with the idea of doing another 5K RPM run Monday night. Of course, if the injector gets stuck open again the dealer will replace it and then expect me to replace all the coils and plugs.

Thanks for all the input.
 

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Diagnostics tools can be limited in what they tell you which is why technicians need to know more than just plugging them in to read out data. :(

If you have a faulty fuel injector it could be caused by electrical problems internally, the wiring or controller. There could also be a mechanical problem internally although unusual, or a problem with fuel pressure. Diagnostics may give a result for some but not all of these. If an injector is physically sticking open another sensor in the system might pick it up. This could be the engine knock sensor and a message like 'Intermittent cylinder' could be given. But the error cannot be specific and it is up to the technician to use their skills looking at seemingly unconnected feedback to link the problem.
I'm not sure what is up with the injectors, but it must be fairly common since VW extended the warranty on these
Not necessarily and you don't yet have any hard evidence of a failure, just your conclusion? How do you know a fuel injector is actually stuck open or have you read this on the internet? It's different with the coils, because people have measured those and proved them open circuit or low output due to shorted turns.

OK you changed the plugs and coils eliminating one source of possible missfire.You admit to not having the mechanical skills and I can't understand where you get the idea of 'stuck open' from without real evidence, either from diagnostics or further tests? For example, If you say an injector is stuck open all the time, then removing it whilst keeping it attached to the fuel rail and the high pressure pump primed would show a continuous flow of fuel from the pintle head. Alternatively and safer, connect an air line? It's far easier to swap over injectors to see if a cylinder fault moves or stays. But then you would need to know how to do that and bleed the rail. If you idled the car so the high pressure fuel pump was up to pressure, I would expect clouds of blue smoke from the exhaust if a fuel injector was stuck open?

With little mechaniclal knowledge, there is one thing you can do but you would have to pay for it: Find yourself a Bosch fuel injection specialist. They work on car and truck injection all the time. They have kit that can check the high pressure spray pattern and operation of individual fuel injectors off the car. They can also disassemble most injector types to repair/replace the pintle or replace the jet nozzle. Their test kit can prove injector operation at equivalent higher rpm higher than your engine runs.You would get back a set of re-conditioned and fully tested fuel injectors, provided they are the type that are not 'throw away'. If there is an issue with a particular spec. Bosch injector they are more likely to share their knowledge than the dealer.

Probably best left to a good technician but mark your fuel injectors before taking it in so you will know if they have replaced any or changed their position.
 

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Discussion Starter #23
The only evidence I have the injector was stuck open temporarily is past experience. When the previous two injectors went bad and were replaced the same thing happened. Does that mean it is an injector? No, as you said there could be several things. I'm just going off past experience. I am going to go out before the car goes back to the dealer and run the car at a high RPM (5K ) for a few miles to what happens. Right now, I'm afraid to push the car. I'm driving it like a little old man.
 

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The best result from anybody trying to solve your problem is to take the car in after it has produced the fault and with faults logged. Not wishing to tell them their job, but they should do a diagnostics scan immediately, save the result then go on to find the problem, clear the fault memory then drive the car to see if the same fault comes back. You should get copies of their before and after fault scans. After getting the car back, if the same fault codes occur, they didn't find the original fault and should try again without charge. :confused: V.W dealerships can be reluctant to hand over any repair evidence like diagnostic scan results. They can avoid this with free warranty investigation or repairs to keep 'secrets' in-house. But if you are paying for their work, you are entitled to ask for those results before they start work and receive them when you collect the car.

Replacing or swapping fuel injectors is an easy job for them to sell as a convincing solution when you have already half convinced yourself, but that may not be the problem? In situations like yours it's best not to add too much information and mislead them into the direction they may want to go which they think will make you happy and get your car out of the workshop quickly.
 
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