I've had my SEAT Ibiza Mk2 for about three years and it's just failed its MOT on the emissions test - there's fuel in the exhaust on idle, and only on idle. It's in the garage at the moment and they're pretty sure the dodgy exhaust reading is down to a misfire on one cylinder. Thus far they've:
- Swapped the HT leads, plugs and injectors around and the same cylinder still misfires, with all the others completely fine.
- Run a compression test. The dodgy cylinder compresses fine, but still misfires.
- The HT leads, plugs, distributor cap and rotor arm are all about a year old.
- The misfire disappears as soon as there's anything on the throttle, it's only on idle.
No mention thus far of the lambda or the throttle body, or the cleanliness of the injectors, since presumably all those would produce problems on all cylinders, not just one. I am going to ask about those when I next see them anyway.
They say the next step is to take the head off and check the seating of the valves, but according to the chap it isn't likely to be that since the compression is fine, as mentioned. After that, the engine will have to come out for inspection basically piece by piece as he described it.
The only other point of note I can think of is that it had a tank of super for an hour and a half's worth of driving two weekends ago, since that was all the garage had. I've heard that the detergent in that can't do any cleaning in one shot but can disturb any large buildups of crud just enough to block the injectors. Does this sound like a reasonable hypothesis?
It's a 1999 Mk2 Ibiza S, 1.4. Does anyone with experience of this model have any pearls of wisdom that could save me the 800 quid or so for completely dismantling the engine? Not that I'm paying that much; I'd rather scrap it. If they can't sort it, it's going to the knackers'.
The astute of you will notice that this is not the first time I've posted about misfiring on this car, on this site. Seems like a never-ending worry.