Fuel Trim Fault Codes

[Bigfella70]

Hi there,

Got an intermittent issue with the following fault codes showing up. Car runs fine, decent fuel and a Cataclean treatment have been used…….which actually cleared the management light at one stage.

Seems to trigger the engine management light at tickover more than when running under load.

Thinking maybe an air leak on the induction side.

Any tips or suggestions most welcome!

 

[AntStark]

Yes air leak most likely

 

[Bigfella70]

Thanks! any ideas on where to start looking / how to trace potential leaks on the M54 engine……

 

[AntStark]

Usual suspects are the flexible boots from the MAF to the throttle body, they split at the concertinas. Any of the pipes that come off those as well. There are little rubber bungs on the back of the intake manifold (near the bulk head) that split and fall off. If you have the secondary air pump (front left clump of plastic) there are a load of vac hoses that come of that and go round the back of the engine. My leak was from the rocker cover gasket failing. Also the PCV system can crack. To be honest I would get someone to smoke test it for you, saves you throwing unnecessary money at the issues
…or make your own ! https://zroadster.org/threads/i-did-a-thing.67817/

 

[Bigfella70]

Thanks for the advice, will update on findings!

 

[Bigfella70]

Apologies, however I have a long overdue update for this thread!

Stripped the intake hoses, DISA valve and idle control valve off for a check and clean up.

Found a very slight split in the upper intake hose where it connected to a plastic elbow. Also the 3.5 mm vacuum hose had seen better days.

Additionally the DISA valve isn’t holding any vacuum, and doesn’t actuate when 12 volts is applied to the terminals with a power probe. Hence new parts ordered and awaited. Hopefully this will see an end of the intermittent engine management light appearing. The car seems to have been running fine but from what I’ve read there may be a perceptible improvement in performance with a new DISA fitted……

Update and photos to follow once the new bits are fitted hopefully this weekend…….

 

[Bigfella70]

So, replacement DISA valve fitted, along with new Febi intake hoses. Also established that the MAF sensor was damaged and not functioning correctly hence that was replaced also.

The car drives and performs very well, however………the engine management light still popped up after a day or so. Showing fuel trim codes.

The car seems to be running perfectly however next move will be a smoke test and possibly change both oxygen sensors. I’m sure that I’ll track down the cause and get it sorted soon!

 

[Peter1450]

Good luck with the fault finding, try not to drop any nuts n bolts, you’ll spend hours in the gravel trying to locate them