Afkari Aziz

Hello,

The car has started to misfire cylinder 5 and sometimes cylinder 1 but that usually goes away for cylinder 1. Cylinder 5 has new coil plug and new spark plug. Weird thing is when clear fault code and the car stopped misfiring on idle. I have test driven and when it reach above 2k it will start to misfire a little when i bring to stop. I suspect is the o2 sensor or MAF sesnor even worse the fuel injector could be a culprit. No coloured smoke coming from the exhaust. Please adviceeee.

nd-photo.nl

Check/service the injectors. Misfire is usually a very "local" issue, I would not expect an O2 sensor to be the culprit. It will sense the difference when measuring, but I don't think it will be the cause for your misfire issue.

Word of advice:
-Service all injectors while you are in there, preferably by a reputable company
-Else replace the rubber rings and if you can also the filter baskets
-Check the replacement interval for the O2 sensors and replace if necessary
-If you have something like a fuel dampener/regulator, replace or at least check it if possible

Afkari Aziz

I have dived into to check the spark plug and fuel injector and cleaned the maf and throttle body. TBH CGI is quite hard to remove certain parts. I still get misfire on cylinder 5 and i checked intake mainfold which is single flap type. The mbar is 380 and when i rev up to 2k then let go the mbar dropped to 180 then it shudders before it becomes smooth. same thing other way if i rev to 2k rpm then i can feel a bit shuddering and mbar dropped to around 200. I was suspecting the intake mainfold with huge carbon pile up on the valves around cylinder 5. Here are the photos i have investigated.

spark plug from cylinder 5.

cylinder 4

cylinder 5

cylinder 6

fuel injector from cylinder 5, cleaned throughly

i cleaned the fuel rail and holding pressure around 55 psi. cleaned all the fuel injectors.

Afkari Aziz

Just used compression tester and is this compression low or just ok?