Engine Hunting - Help Please

[richard.tarlton]

Hi All,

 

I have brought a 52 plate xsara picasso 1.6sx ( petrol ), the car seems fine. But after a drive of half an hour or so, the engine hunts up and down the revs a bit when idle, and has cut out on me particulally when reversing, ( unless quite a few revs are put in to it ).

 

I have done some research on this ( good old google ), and resolves seem to vary between MAP sensor, the lambada valve ( unlear if there is only one ) or an air leak somewhere, but dont get any hissing from engine.

 

Any suggestions on how to troubleshoot this before buying parts would be much appreciated.

 

Many Thanks in advance.

 

Richards

[paul.h]

Welcome to the forum.

 

First thing to do will be clean the throttle plate and body with something like carb cleaner or a cloth damp with white spirit (turps). Carbon build up can affect the air flow around the plate or cause it to stick a bit. Also check the air filter is clean. You can look for any hose splits but since you have a MAP sensor and not an air flow meter any air leaks would be measured so may not give much of a problem.

 

A code reader with live data may tell you if the MAP sensor is faulty but if it runs ok normally then it is may be ok but you could see if it is full of oil. Similarly, live data will show if the exhaust inlet lambda sensor is faulty - it should normally be switching up and down in value as it reacts to fuel mixture changes. You could also use one to check if the engine temperature sensor is giving a normal reading.