m3 evo misfiring

[stephen pook]

Hi all.

My first post on this forum ... ( formerly a TVR owner). I've owned a 1996 M3 Evo since December and have had no problems at all until recently...

An intermittent fault has developed which now occurs very frequently. Once the car is warmed up and has been driven for a while power drops significantly and the car idles poorly. I have taken it to a knowledgable local specialist who has discovered that the car is firing on cylinders 4, 5 and 6 only and a Lambda sensor fault is recorded. Changed the lambda sensor and no difference. Once the car has cooled down after acouple of hours or so it runs fine but once warm and driven for a bit ... same problem.

After further test it transpires that the injectors to the front three cylinders shut down when in fault mode. Mechanic has suggested a new ECU may be the answer. ( He has checked all the wiring, relays connections etc.)

Any other ideas anyone? All useful suggestions welcombe as this may save me the expense of another ECU.

Cheers,

Steve.

[stefd]

Seeing as it only happens when the engine is hot has the coolant temperature sensor been checked or the wiring inspected? Quite common for these to fail and they're only cheap.

Not a definitive answer rather just a thought.

[stephen pook]

Thanks Sted. Will have a look at that. Would that not come up as a fault code or some sort of warning light come on? That's the problem... the only indication of what's wrong is the lambda sensor fault code.. even after the sensor has been changed.

[ian332isport]

Are you sure you replaced the correct sensor ?

There's one in each manifold (one sensor for cylinders 1 to 3 and another for 4 to 6).

Ian.

[fixedwheelnut]

Check the ignition coils especially if the engine has been steam cleaned at anytime, water can get in there and never really dries out completly unless they are removed and cleaned, as the engine gets hot the water steams up the inside of the coils and causes misfires that then cause the catalyst protection to shut the fuel off.

[stephen pook]

Thanks guys. Definately replaced the correct sensor. Will check the ignition coils and clean out or replace.

Thanks again,

Steve.