bad plugs........hmmm?
#11
05-11-2010, 03:28 AM
It depends on what you are identifying as a misfire. Is it genuinely a misfire or are you feeling hesitation due to incomplete combustion?. A weak spark is not the same as no spark or even a retarded or advanced spark. Your car uses the CPS to detect a misfire which is rather primitive so I wouldn't rely on that if I were you.
The difference between an old school mechanic such as myself and a modern "technician" is the new guys rely almost exclusively on what the ECU is telling them whereas the old boys use the ECU along with experience gained in the days before ECU's were around. Of course I cannot tell exactly what is wrong with your car without seeing/hearing it all I can impart is possibilities. Using knowledge of how are car runs coupled with a process of elimination is often the best way of determing an issue.
One other thing to note is that fuel delivery can also be affected by te state of the oxygen sensors on a petrol car. These send an electrical feedback to the ECU based on the concentration of free oxygen within the exhaust gases. If it thinks there is too much free oxygen due to an air leak in the exhaust somewhere it will richen the fuel mixture to compensate which again may cause and issue. Also an air leak somewhere else in the air/fuel system e.g. your inlet manifold or associated piping or even at the brake servo can cause a situation where the ECU is trying to richen up the mixture again resulting in hesitation.
If you can actually feel the car miss as it were then again following the electrical system as I have previously described and also consider a sticky injector, Try and reseat the electrical connectors at each injector by removing them and putting back on. Also try an off the shelf injector cleaner to remove the possibility that a build up of varnish on the injector needles may be causing them to stick and that the lack of fuel or insufficient fuel reaching the chamber is presenting itself as a misfire.
Draw yourself a flow chart so you know what you have looked at so you don't go round in circles.
The difference between an old school mechanic such as myself and a modern "technician" is the new guys rely almost exclusively on what the ECU is telling them whereas the old boys use the ECU along with experience gained in the days before ECU's were around. Of course I cannot tell exactly what is wrong with your car without seeing/hearing it all I can impart is possibilities. Using knowledge of how are car runs coupled with a process of elimination is often the best way of determing an issue.
One other thing to note is that fuel delivery can also be affected by te state of the oxygen sensors on a petrol car. These send an electrical feedback to the ECU based on the concentration of free oxygen within the exhaust gases. If it thinks there is too much free oxygen due to an air leak in the exhaust somewhere it will richen the fuel mixture to compensate which again may cause and issue. Also an air leak somewhere else in the air/fuel system e.g. your inlet manifold or associated piping or even at the brake servo can cause a situation where the ECU is trying to richen up the mixture again resulting in hesitation.
If you can actually feel the car miss as it were then again following the electrical system as I have previously described and also consider a sticky injector, Try and reseat the electrical connectors at each injector by removing them and putting back on. Also try an off the shelf injector cleaner to remove the possibility that a build up of varnish on the injector needles may be causing them to stick and that the lack of fuel or insufficient fuel reaching the chamber is presenting itself as a misfire.
Draw yourself a flow chart so you know what you have looked at so you don't go round in circles.
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