A few days ago, my 2005 Audi A4 1.8T QT (65,000 miles) started to misfire. The car would shake, stutter, and hesitate, mostly noticeable at idle or 1st gear but also during driving at times. Check engine came on and got it checked at autozone and came back as P0304, cylinder 4 misfire (vacuum leak on engine?). If I try to accelerate quickly the car would shake noticeably and the CEL would flash, so I've been trying to keep the RPM's down. I changed all four spark plugs and the problem is still there. And the coil packs are only a year old. Sorta getting frustrating figuring out what is causing this...I also put into fuel injector cleaner. I did some searching and found out it may be a vacuum leak but I looked and didn't see anything, but maybe I'm not looking at the right hoses? Any help would be appreciated, thanks.

 

swap coil packs from cylinders 1,2, or 3. see what happens. I don't think it is a vacuum leak, that would affect the whole engine, not just one cylinder. Check to make sure the coil pack is plugged in properly and the injector is plugged in properly.

 

If it was a vacuum leak it would most likely have a random misfire code, while the vehicle is runing unplug each individual coil seperatly and watch the engine for any change in idle...once you figure out which cylider is misfiring (#4) switch the that coil with one of the non misfiring cylinders and if the misfire follows that coil then its a bad coil, if it doesent then start looking elsewere.

 

sorry dident mean to repeat

 

Hmm... well last year one of them failed, and the car ran way worse, and I replaced all four. I'll try it tomorrow and see. But where is the number four cylinder? lol

 

4 is firewall

 

I swapped the number 3 and 4 coil pack and the same code came up. So its not the coil packs. I really want to get this fixed ASAP preferably on my own, I'm worried there could be engine damage if I keep driving it. Have no clue where else to look, any suggestions please!!!?

 

try switching out the fuel injectors. if you have a noid light put that on it. you said the plugs are new, but did you take a look at them recently. are they wet with fuel or oil?

 

The old plugs were fine, didn't need to be changed, but changed them anyway. Well I swapped the coil packs on cylinder 3 and 4. And the car seems to run a little better for some reason or maybe I'm imagining it. But it still stutters at times. I cleared the code, and drove it for 20 miles and no ECL yet, but expect it to reappear again because the problem is still there. But I'm hoping it will show number 3 misfiring so then I'd be confident it be a coil pack. If its P0304 again then it'd be something else.

So if it shows as P0304, I'd check the injector I suppose. So how you remove the fuel injector?

 

CEL flashing is always a coilpack, don't swap, change all four and keep the rest for spares. The reason why is because you have put strain on the other packs when one of them doesn't work. Don't get into fuel injectors before you actually replace the packs, they're really notorious for failing on the 1.8 turbos.