Ongoing intermittent "check engine" problem - Alfa 159 2.2JTS
Wondered if anyone here had any advice, tips or pointers about this problem.
I've had an intermittent "check engine" warning light (solid yellow) coming on and off for about the last 6 months. The car (159 2.2JTS 4 years old - out of warranty) has repeatedly been back to the dealer but they have been unable to clear the problem.
The warning light comes on, sometimes it goes back off again after a day or two, other times it stays on until it goes back to the dealer. Sometimes it goes off the day before the dealer is going look at it, other times it is on when it goes to the dealer. After I get it back from the dealer it can be clear for a few hours, a few days or even in the best case up to a month or so.
I can't spot any pattern to when it comes on or goes off. When the light is on the engine is marginally lumpier and less responsive, particularly at low speed, but there is no significant drop-off in power.
The dealer first diagnosed this as a stretched timing chain and replaced the timing chain (quite expensive). At that time the engine was significantly lumpy and improved considerably after the replacement of the timing chain however the intermittent check engine warning light continued.
Since then each time it has gone back they have fiddled with various things, mostly focussing on the inlet manifold sensors and the connectors to the sensors. Most recently they replaced two sensors (inlet mainfold ?), the connectors and the associated wiring loom and I think they thought they had it licked.
But the check engine light has come back on again.
So what advice do any of you guys have ? What else could it be ? What could/should the dealer be doing ? Anyone else come across this problem ?
Thanks in advance for any pointers.... please treat me gently I'm not a car techy buff.