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18 Posts
Discussion Starter #1 (Edited)
Hi all, I am working on my sons 2010 Passat Wagon 2.0T (CCTA engine) which has 286,000 kilometers

We bought it used this summer knowing it ran rough until warmed up, at which point it runs like a champ.
I have VCDS and the OBD2 scanner and it was almost always showing P0303 Misfire (cylinder #3). Occasionally it would show P0300 and P0302 or P0304, but never P0301.
So, I removed the intake manifold and did the walnut shell blasting, yes my son helped lol.
The car immediately ran and shifted smoother however the misfire in cylinder #3 remained when warming up to operating temperature.
I swapped coil sticks around and the issue remained at cylinder #3. Then checked and swapped spark plugs around and still cylinder #3 misfire (gap on plugs was 0.030).
He has been driving it in S (Sport mode) as it felt a lot less jerky until warmed up, likely due to higher revs/more fuel being injected. Then shifts the transmission into Drive once it hits about 90 degrees celsius.
Today I did a compression test and each cylinder produced 125 psi (which I find low but the car really does run great once warmed up). The results were nearly identical so it's possible my compression gauge is bugged?
I have a used fuel injector and am planning to swap this in, it has to be the fuel injector at this point, right?
It must be clogged or dirty or something? I have also run a bottle of fuel injector cleaner in the last full tank and will do an oil change after the tank is topped up.
My plan is to remove fuel injectors 2 & 3, and put the used fuel injector I have into cylinder #2 and put the injector that was in #2, into cylinder #3.
This way if it's still throwing a P0303 code I'll have to trace the injector or coilstick wiring harness to see if there's ample current coming through, it seems like there is ample current as it fires right up even after 2-3 days cold sitting.
Just doesn't make sense to me yet why it gets better once at operating temp unless the ECU then tells the injector to spray normal or something?
Thanks for any hints/tips you may have!

I didn't have my son hold the gas pedal down to simulate WOT, is this required, is that perhaps why the readings were down at 125? I'm happy they're consistent across cylinders but 125psi seems low.
Maybe the mileage is now showing and the rings are down to their wear limits? Could this be affecting the misfire reading?

Thanks all

18 Posts
Discussion Starter #2
Replaced fuel injector #3

Soooooo, I removed the suspected fuel injector (cylinder #3) and moved the injector from cylinder #2 into #3 and then put a used injector into cylinder #2.
Buckled it all back up and it is instantly better and feels like it is running normal, almost lol.
It now drives and shifts very smooth in Drive, no longer needing to be in Sport to ensure non-jerky shifting and misfires.

However, this morning I started the car and could hear it sputtering. the engine light started flashing and scanning the codes with a cheap ODBII scanner gave me the entire range of misfires - P0300, P0301, P0302, P0303, P0304.
Now, it was -15 celsius this morning and after it was running for maybe 2 mins the sputtering stopped and I took it around the block with no misfires or sputters.
Shifted great, no jerky movements and the coolant temp was only reading at 45 degrees celsius at this point. It usually gets up around 90 degrees celsius.

My next check is PCV to see if the diaphragm may be ruptured. But I do believe the plugs, coil sticks and fuel injectors are all fine. They're not new but the plugs looked to be in great shape despite the misfiring in cylinder #3 even.
The intake ports/valves were also walnut blasted recently (from my earlier thread a month ago) and has already showed signs of oily gunk on the intake plates and valves when I removed this time to replace the fuel injectors :-(

My gut tells me to replace the entire PCV but I'm going to try replacing just the diaphragm component first.
I'll also clean the MAF sensor and after that, I will check and in required replace the diverter valve.
The air filter is clean and recently was replaced anyways.

Anyone have any comments or suggestions on any other culprits to check while I'm in there picking away at things?
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