I have recently had a full decat fitted to my wrx (harvey upipe) and turbo back. I also had a carberry remap at the same time. I have basic mods on engine; 255 fuel pump, prodrive y pipe and doluck filter. Also have recent service.

As I have carberry, I now have a knock sensor which basically flashes the engine light, but I find that I get this almost everytime I get to 6000rpm - even tonight when temps are 9 degrees. Is this normal?

Also, I find that I get fuel cut at 3000rpm. If I hold the throttle at contant revs and hen accelerate hard I hear a loud bang and hesitation which I think is fuel cut overboost. I first notice this on motorway in 5th gear but I also get it in 4th and 3rd.

Is this normal and do I need to buy any parts to fix this?

 

Could be two different things, although need a mapper to comment really. Knock at 6k *could* be engine noise, but if it's the stock knock sensor that has now been "mapped" by the carberry to flash the CEL, sounds like, um, you're getting knock. Back off!!

At 3k, that sounds like overboost. If remapped properly, shouldn't be doing that.

Internet diagnosis (i.e. can't be trusted upon lol) is that you need the map attending to.

 

I found using the cel as a knock indicator annoying and causes you to get paranoid , it does tend to be a little sensitive , mine used to flash even though many logs never showed any issues ,
Regarding the cut issue , are you sure it's fuel ?
And not ignition related ,
I had plug gap problems ( stock cap was to large , dropped down another 0.01 )which I was convinced was fuel but it was just blowing the spark out ( but didn't show as a misfire count in the logs )
If it is the map it's very poor and drop your current mapper like a stone and seek other pro advice
Alternatively get a laptop and cable , change your plugs and gaps and have a look yourself what's going on

 

Its probably true that the sensor makes you a bit paranoid, the first time I saw the engine light my heart sank! Its also hard to research knock on an impreza without reading about rear shocks!

I like to rev a petrol, but also want to drive the car with mechanical sympathy and I dont know if the car knocking before or if it is just because of a problem with the remap or not?

On the fuel cut, Im not sure it is overboost but the mapper is sure and he is now sending me a new part to prove it and hopefully fix it. Basically if i hold the revs in gear at just under 3k and then floor it I get a hesitation and a bang before the car goes for it. I think the mapper would have detected plug problems during he map.

Part of modding a car is learning the hard way I suppose but so far Im a bit scared to use the extra power I now have in case of more problems.

 

Without wishing to play devils advocate , regarding the mapper knowing about the plugs , he should also know about potential over boost and or fuel cut issues that could arise , wether it be recommend alternative set up , boost solenoid swap ect or the map itself
Tread carefully summat don't seem right here