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Discussion Starter · #1 ·
Just sharing my current issue with plan

I keep my Eos in tip top shape and keep up with all service recommendations by the book.
But last night my engine light came on - I already knew what the code was (Cylinder 4 misfire) as I have an Automatic ODB code reader. So I knew it could be spark plugs, spark wires, vacuum leak, fuel injector, etc.
Turns out to be a bad fuel injector. I'm going to let the Dealer repair it since the price was comparable with 2 other repair shops. All offered $1000 total out the door. Labor is the most expensive part due to removing the manifold. Plus it comes with a warranty so I'll bite the bullet as I need my baby in tip top shape.

Anyone else out there experienced this issue on their baby?
 

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Fuel injection is usually very reliable and I would have gone for the plugs or spark coils first, the latter being a very common problem. What evidence have they got that it's the fuel injector and nothing else? For the amount you are prepared to spend I would have done the easy thing of swapping over the plug and coil from cylinder 4. If the fault moves, then it's coil & or plug but if it stays on cyl. 4, then dig further into the injector.

Simple resistance checks (although not conclusive) can be done on a fuel injector without dismantling work. I think I might also do a compression test on each cylinder because diagnostics won't tell you if there's a more serious problem with a valve or piston. These are all easy cheap labor things to do as part of further investigation before tearing into hard to get at parts when a computer fault code isn't telling you much. That would be my plan. :)
 

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Discussion Starter · #3 ·
Fuel injection is usually very reliable and I would have gone for the plugs or spark coils first, the latter being a very common problem. What evidence have they got that it's the fuel injector and nothing else? For the amount you are prepared to spend I would have done the easy thing of swapping over the plug and coil from cylinder 4. If the fault moves, then it's coil & or plug but if it stays on cyl. 4, then dig further into the injector.

Simple resistance checks (although not conclusive) can be done on a fuel injector without dismantling work. I think I might also do a compression test on each cylinder because diagnostics won't tell you if there's a more serious problem with a valve or piston. These are all easy cheap labor things to do as part of further investigation before tearing into hard to get at parts when a computer fault code isn't telling you much. That would be my plan. :)
Thank you for your feedback - much appreciated. The coils and plugs were replaced last year. When I brought it in today - They swapped the plugs and wires from another cylinder and it proved to be something up with Cylinder 4. They did do a resistance check like you mention. They didn't do a compression test. I'm just going to have the fuel injector replaced and hope that fixes it. I did notice the car idling really low at times the last couple weeks, also a couple times starting the car didn't start the first go around, and after starting the car was rumbling a bit before warming up.
 

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Hope you get it fixed o.k. Unusual fault though. Has the fuel filter been replaced regularly at the intervals? If the injector resistance was o.k it sounds like the pintle is sticking or the end has burned up? You can usually hear an injector 'click' when powered with 12V. If it powers, takes some small current and doesn't click like the others, it must be dead.
 

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Fuel injectors can be tested by firing/pulsing them for a fixed time (say 500ms) and measuring the pressure drop in the rail. Compare all 4 and the bad one(s) stick out like a sore thumb; or compare the results to known good values. I believe some scan tools have a program to do this.
 

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Good suggestion. Spending a little time doing the right kind of diagnostics can save a lot more time and money on the alternative of a partial teardown. The fuel rail pressure is usually measureable with most diagnostics but not sure if that test program is in V.W diags? Alternative: Prepare in advance to get access to each injector terminal, turn on ignition to get rail up to pressure and turn key off to stop pump re-pressurising, The fuel rail should still hold pressure. Touch 12 volts on the injector terminals repeatedly in 1/2 second bursts. If the fuel rail pressure, drops the injector must be opening and isn't stuck closed. If you can get No. 4 plug out, give the hole a good sniff afterwards and you might smell the gas. This might find an obvious injector fault but won't tell you if it's partially sticking or performing badly at high revs. I used to think the ECU monitored voltage to coils to detect misfires, but I think they use the knock sensor? Injectors going bad are uncommon. Injectors of the serviceable type are usually serviced in sets because if one has failed others may follow. Check on the Bosch injectors used because most of them have a very fine filter inside which is why I mentioned fuel filter maintenance. If that filter is blocked the injector could be opening but starved of fuel. I keep telling wifey not to run the gas tank down to near empty.
 

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You should probably invest in VW-specific diagnostic equipment (see the link in my signature), as generic OBD readers will only tell you a small fraction of the story. OBDeleven or VCDS will tell you more about what's going on with the misfire that was logged.
 

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Misfire detection with diagnostics like VCDS doesn't tell you if a coil, wiring to it or an injector is faulty. Misfire is usually determined from a combination of engine sensors e.g Crank position, camshaft position (if present) knock sensor and rpm versus throttle. The ECU uses an 'algorithm' to arrive at a result.

The ECU monitors the pattern of normal responses from these sensors and puts up a cylinder misfire fault code after a certain number of misfires have been recorded. On its own, you cannot go much further apart from guess at plugs,coils, injector, bad valves or fuelling. Engine ECU tuning if done badly can also be a culprit.

However, VCDS and possible OBD Eleven? has an option to ENABLE realtime misfire event logging of results which are stored in the ECU and can be read out. This is very fine data logging EACH misfire with rpm, other things, and a time stamp for each event. With that kind of 'fine grain' log data the competent mechanic can try different rpm tests, even put some propane in the induction to learn more about when misfires occur. I know propane sounds scary, but done carefully under controlled safety conditions by trained technicians, it allows mixture and EFi mapping loop response to be tested for a respose to over rich fuelling, or an injector failing.

If I was the competent garage mechanic I would add this fine grain misfire detection logging to my list of procedures. Coils and to a lesser extent injectors, are most likely to fall over at high rpms. You can repeat the fine grain misfire detection at various idle rpm to see if they only occur above a particular rpm and with slow and fast throttle changes. The same is true of injectors. Even if partially starved of fuel or producing a bad pattern, injectors usually work o.k at low idle.

 

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Just sharing my current issue with plan

I keep my Eos in tip top shape and keep up with all service recommendations by the book.
But last night my engine light came on - I already knew what the code was (Cylinder 4 misfire) as I have an Automatic ODB code reader. So I knew it could be spark plugs, spark wires, vacuum leak, fuel injector, etc.
Turns out to be a bad fuel injector. I'm going to let the Dealer repair it since the price was comparable with 2 other repair shops. All offered $1000 total out the door. Labor is the most expensive part due to removing the manifold. Plus it comes with a warranty so I'll bite the bullet as I need my baby in tip top shape.

Anyone else out there experienced this issue on their baby?
Spark plug and boot on 4th cylinder
 

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The OP confirmed the fault found was a bad fuel injector not the plug or boot which should have been the first easy and obvious thing a mechanic would have checked?

Diagnosing problems on modern complex cars rarely gives a one line solution. A good workshop will use guided fault finding to run down a sequence of possible fault causes by eliminating possibles to conclude the problem. It's even more important for a DIYer to follow logical steps even when something is confirmed o.k with certainty and can be excluded.
 
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