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Re-acuring Check Engine light problem

I am having an issue with a check engine light that keeps popping up. When it first appeared the fault code was for misfire in cylinder 4. I took the opportunity to change all the spark plugs with factory NGK and all ignition coils with VW coils. I had the engine fault codes erased. It has been two weeks and engine was running great, but in the last few days it has been idling rough and the check engine light came on again. The rough idling happens at about 1100 rpm and u can feel vibrations in the car. I had the code checked again and it said misfire in cylinder 4. Anyone have thoughts on what this could potentially be??
 

GolNat

Drag Racing Champion
How many miles are on it? Has it had a carbon cleaning? Did you check the gaps on the plugs? I know they come pre gaped but one of mine was off.
 

JW with a VW

Go Kart Newbie
I know it sounds simple, but also check to make sure where the harness connects to the coil pack is secure. If the little clip is missing or broken, it may be causing a bad connection...just a thought.
 

zrickety

The Fixer
Yeah I would think it's a fuel injector. Try some injector cleaner with a tank of top tier (Shell 93 or similar).
Drive it hard for 30 min (3000+ rpm).
Let us know how it goes.
 
I have been driving with the fuel system cleaner for about 4 days and not seeing any improvement. My check engine light is still on. When I checked the connections they were connected all the way up the end of the ignition coil. But I noticed that I could slide them off with out having to push the clip. Could this be the issue? They need to click into place. My EPC light came on for a min when I started it up yesterday. Then shut off as I started driving. Any other suggestions ?
 

JW with a VW

Go Kart Newbie
Could be a bad coil pack still...you can try swapping number one and number four pack, clear the code and drive it for a bit. If the code changes to that cylinder, then you have found the issue.
 
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