Cylinder 1 misfire and loss of power.

Hi everyone,

I’m new to the forum so bear with me!

I have this issue with my A4 (B7) 2.0t cabriolet. In normal driving conditions when warm or cold the engine seems to run fine. No knocking, loss of power, strange noises or vibrations. It seems to be running as it always has. 

However, when I try to get the engine to run at very high load (ie greater than 90-95% load) such as accelerating in 5th or 6th gear up a hill, the engine light flashes, there is some juddering from the engine bay and zero increase in power output. Power levels don’t seem to drop, they just don’t increase. 

The check engine light flashes then sometimes goes out and sometimes stays on. 

If I stop asking for power then the car goes back to normal. 

Interestingly this doesn’t happen at all in gears 1-3 and only in 4th if I plant my right foot going up hill. 

Ive got an OBDII reader (which I’m aware isn’t as comprehensive as VAGCOM) that gives me some basic info and lets me reset the codes. 

I get code P0301 - Cylinder 1 misfire detected. 

Throttle position 88.24%

MAF air flow rate: 103.38 grams/sec

Timing Advance: 8.0 deg

Speed: 98kph

Long term fuel % trim-Bank 1: 1.56%

Engine rpm: 3173

Intake air temp: 19.0 deg C

Short term fuel % trim Bank 1: 15.62%

Engine coolant temp: 93.0 deg C

Runtime: 00:05:38

Engine Load: 100%

Fuel system status: 2) Closed loop: Using O2 sensor for fuel mix.

Ive done a fair bit of googling and most of the others with the same error code had the misfire occurring at all or most of the time, not just when under heavy load. 

I’ve swapped the coil packs and spark plugs between cylinder 1 and 4 with no change (makes me think they’re both fine) Although I haven’t swapped for new ones yet. 

Any thoughts? Wondering if there’s a bit of carbon deposit partially occluding the fuel injector for cyl 1? Although I’d have thought that would cause problems at lower loads as well. 

For what little it’s worth I popped a bottle of Redex in with a full tank of 98-99 RON BP petrol. So far used half that tank with no change. 

Doesn’t seem to be getting worse at least. 

Thanks for the help!

Matt