2003 200 efi 2.5l cylinder

My engines top port cylinder is not firing and I think I have an injector problem on that cylinder. Lost power last week and checked the fuel pressure which was reading 58psi out of the vst at idle and fluxuating 40-60 under load. Checked to see which cylinders were firing while during idle by unplugging coils one at a time. all the cyl had a rpm loss except the top port. tried swaping top port coil and wire with another cylinder and the problem stayed with top port cylinder. Replaced all plugs with new gapped plugs, the top port cyl still dosent seem to be firing at idle but motor ran well and got 5K rpm. After about an hour of operation the max rpms dropped back to 4500 and I checked all plugs. The top port plug was black and rough speckeled and all other plugs were looking the same normal light brown. Changed that plug with new and can get 5000rpm again, but....

I think this cylinder is not getting any fuel at idle and is running very lean under load. causing the piston to degrade/overheat and fowl the spark plug with aluminum.

Compression is 120psi on all cylinders. checked this twice.
The top port coil/plug is sparking fine.
engine temp gets to 150deg
No smartcraft alarms
Idle is very low due to the fact that this cylinder is not contributing at idle.
If anyone has any comments on this I would appriciate hearing.
Thanks

Re: 2003 200 efi 2.5l cylinder

Pull the head and your going to find one of the following:
1) Scuffed exhaust port
2) Bad head gasket
3) Reed broke/chipped and damaged cylinder
4) Cylinder lean from clogged injector or ECU problem

Re: 2003 200 efi 2.5l cylinder

I had exactly the same problem apart from the speckled plug. The number 2 cylinder would just stop firing.
Put in a new MAP sensor....all fixed.

The sensor made the cylinders run richer due to not picking up the higher vacuum and the coldest cylinder, being the top Port (No.2) fouled and stopped firing.

Try taking the MAP sensor out and cleaning it with CRC contact cleaner as the MAP tends to get full of oil. Also take off the throttle body (4 bolts) and mop out the oil in the bottom of the intake chamber as that will mist and block the sensor again.

Check to make sure the speckled plug hasnt got water on it as then it would be the head gasket.

good luck.