P0304 engine lights (cylinder 4 misfire)

Asked by Jun 04, 2017 at 03:51 PM about the 2011 Volkswagen Jetta S

Question type: Maintenance & Repair

P0304 errors for cylinder 4 misfires. dealership replaces spark plugs. 4000 miles later same error and replaces fuel injector in less than 20 minutes. 5 miles later Jetta gets towed to dealership with P0304 and EPC engine lights on. replaces ignition coil and wire set.
dealership insists that it's just a big coincidence that the coil failed immediately following their injector replacement. according to the dealership it's impossible that they caused it. just wondering if that is true? Thanks.

11 Answers

580

So was #4 ignition coil replaced with spark plugs the first time. There was probably nothing wrong with the injector. The ignition coil was faulty. Rarely ever see injectors fail. If they got you to do an induction cleaning when you had the spark plugs replaced. That would have caused the injector to fail.

they replaced spark plugs only on 1st repair. didn't see anything about induction cleaning... at 2nd visit, i stated that based on error the wires/coil should be replaced, but they said that they will check on their own and replaced the injector instead. only to return 5 miles later

580

They replaced injector for no reason. Knowing a p0304 represents specific cylinder that is misfiring.

55,265

Since we were not present when the diagnosis and repair was done all we can do is assume. We all know what happens when we assume. Get it fixed and let it go and move on.

580

I understand that. If it was an injector. It would have set a p0300 for random and if there was a problem with the injector. A p0204 would have set for open inj driver or short to ground. Anybody knows that's a technician. If the misfire is cylinder specific. The computer is going to name that cylinder. P0304. I don't assume.

580

I know what happens when we assume. That gentleman was charged for an injector he didn't need. If I assumed like you claim. I would have to close shop.

55,265

Not necessarily. I have seen a P0308 normally suspected to be plug, coil or related wiring actually be a faulty injector. You certainly assumed here as I am pretty darned sure you were not present at the shop during this car's diagnostic testing.

580

Again I didn't. There would be other codes associated with that code. Random misfire, lean condition, base timing exceeded minimal threshold.

thanks for your help. clearly, the dealership got one over on me...

580

No problem.

11,035

when you take your car to the dealer you really need to stay on top of them. I had a power steering pump blow off all its pump fins due to frozen fluid in my pump during the winter. took me 5 times of driving to the dealer to get it fixed. they kept telling me its normal when i knew for a fact that the car steered like a dream a month before the cold weather happened. The dealer always trys to screw you and charge you for more then you really need. If its warrenty work take it to the dealer other wise find a good VW/Audi specialist to look at the car it will be cheaper and done right the first time not a little here a little there.

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