Mordajedna

Engine misfire after your heater core got f**ed you probably got air pockets in the engine. Get a coke bottle, fill it up with water wrap its thread in rubber glove- makes a nice seal- open your radiator cap turn on engine. Fit the bottle neck into radiator and observe bubbles..when they re gone your engine should work ok. If it keeps spitting coolant from expansion tank and you keep getting misfore- get compression test it mght be HGF as it was in my case.

Had same problems... 1) Iddling check if you can feel enigne to work iregularly- its 6 pot so you should not feel it working at all (I MEAN feeling it- no vibrations at all !) 2) Check if your coolant is ok- if shes not spitting it out via expansion tank sleep well its not HGF (as it was in my case) 3) Faulty lambda on exhaust manifold may cause it- verified by code inspection. 4) I guess P0301 P0302 P0303- engine misfire- check spark plugs and coils. 5) Faulty/blocked precat on exhaust manifold. 6) Faulty throttle position sensor- but id say car would feel underpowered.

My bet- main cat. * Your o2 sensor is located behind it- other lambdas are before precats- it is unlikely they will detect faulty cat. * 0420 is cat efficency below treshold- assuming your main cat is all good and if you install decat exhaust manifolds- you will not get this error (youre not supposed to get it anyway). you can get new cats from ebay for approx 50-80 gbp or 2nd hand one from ideally 05 vehicle for....well around same price. I had similar problem and it was main cat. I removed the underfloor cat pipe and rather large chunks of my main cat fell out of it- cut it out until i got new one- you can do the same and if you are annoyed by check engine light- disconnect battery for 3 min and connect it again- light wont come up for about a week.