Hello, I'm new... any help would be appreciated

[Juliet]

Hi,
I have had the pleasure of driving my 2004 JTS 156 since 2010, with the odd expence here and there. I fell in love at first sight, and understood that she may be high maintenance.

In the last 3 months, I've been battling with the dreaded "motor control system failure". I have taken her to my knowledgeable mechanic who diagnosed that she was running lean. He has, with my blessing, replaced all coil packs, spark plugs ('cos they were sitting in oil!), subsequent gasket seal, timing kit (it was due anyway), and the most recent visit, both pairs of forward and aft catalytic Lambda sensors. A week and a half after getting her back, and after a full refuel (not sure if related), the advisory was set again. Does anyone have experience with this, and possible advice? I really don't want to contemplate replacing the cat.

Cheers   

[Citroënbender]

Not sure where the experts are this week...

The "MCSF" warning can come up with a good number of causes. Bazzbazz is probably the person whose judgement I'd go to the bank with. Hopefully he'll pop up soon enough.

[Craig_m67]

Ouch... that sounds like an expensive approach (replacing everything).
No doubt the ECU codes read by the mechanic suggested these items were the issue ?

Hopefully Bazz can wade in shortly and ask some insightful questions that will tighten the scope

[Jekyll and Hyde]

Ouch... that sounds like an expensive approach (replacing everything).
No doubt the ECU codes read by the mechanic suggested these items were the issue ?

That was my thoughts exactly.  I'd take an uneducated guess we are dealing with a non Alfa specialist, and they appear on the surface of it to be employing the shotgun approach, although information is a little light on here, and I hate to can a mechanic without having ALL the details to hand - particularly in this case, the ACTUAL fault code(s) retrieved from the computer.

But questions must be asked, when you replace 4 JTS coil packs at once (especially given the cost last time I priced one)? On a JTS, they either work, or they misfire noticeably (usually somewhat intermittently). 4 coil packs playing up at once would make for a pretty undriveable car.  It is however possible to end up with 'ignition failure' codes across all the coil pack, even though there is nothing wrong with the coil packs but rather something else (including a flat battery at some stage since fault codes were last cleared) - a trap for inexperienced players.  But replacing 4 coil packs in the hope of fixing a 'lean' condition?  While it is possible for the oxygen in unburned fuel mixture to be read as lean by an oxy sensor, its not common - and again, the car would have been nigh on undriveable with 4 coilpacks playing up.  I also don't recall ever seeing a fault code for a 'lean condition', so I'm wondering where that diagnosis has come from.

To do 4 oxy sensors at once is perhaps a little less unusual, and not on the whole a completely unreasonable proposition, but again given the cost of the sensors, why not determine the faulty one(s) via reading of the live data on the scan tool?  Not a perfect solution if you suspect that they're all reading a bit out, but generally in my experience, they're either dead or alive on the live data, and if alive, they don't cause fault codes.  Doing all 4 at once given the previous visits works, starts to smack of just throwing parts at it and hoping - hence my wondering if this is an experienced Alfa specialist, or some other workshop.

Spark plugs and timing belt, well, they're good things to have done anyway, being service items, and spark plugs are not a bad starting point if you DO have ignition failure codes (though not usually with a set of coil packs at the same time!).  Timing belt for obvious reasons, but the way the first post is presented, I wonder was the timing belt done because its due, or in the hope of fixing the fault?  The cam timing can of course be checked without the need to replace the belt...

Certainly much more information on the fault and circumstances is required to make a fair judgement, but to my mind, the evidence so far presented suggests they're trying their best, but they don't really know what they're looking for here...

[bonno]

Hi Juliet
In addition to my PM sent to you earlier and the several responses to your post, I have attached the following link that explains the "MCFS" warning light and how the diagnostic tool connected to the cars computer is used to diagnose fault code/s and enable remedial action in resolving the issue.
https://www.obdautodoctor.com/scantool-garage/how-to-read-and-reset-the-check-engine-light
Hope this helps
bonno

[bazzbazz]

Sorry guys, but without actually knowing what, if any, error codes are causing the MCSF to light up is like asking "how big is a ball of string", and the ball of string is in a sealed box, buried 3 meters underground, and on Mars.   

Baz