I think i found my 2.5 rich problem!!!!!

[skydog]

The Engine head temperature sensor!! I went to ohm it out and it comes back as just open!! So that would be just like taking the sensor off! RIGHT?! Now how much richer does a 2.5 run with this sensor off? Will a head temp sensor from any V6 merc work, like a 95 200??
Thank you Skydog

[MTCM]

What motor and ECU are we talking about? Where is this head sensor installed on the head? If it's a 260, the head temp sensor may not contribute to ECU Injector Pulse Width computations. Need more info on motor......................

[skydog]

It is a 260 with a A48 box. The sensor is the the top right head.
Thank you Skydog P.S. Motor runs fine for about 30 min then it just acts like it goes FULL RICH.

[skydog]

It is a Z-port what is the easiest way to see if it is getting water in the motor?
Thank you Skydog

[steve]

The temp sender on the stbd head is just your overheat alarm. There is no head temp sender to do any compensation in the 260 ( Z-port) ECU only on the ProMax and std Laser ECU's. The air temp sender is the only sender to make adjustments for temp. It should read from 5-10K depending on air temp ( its on the stbd side under the starter on the front 1/2 of the block--2 tan wires. The one on the head is open until the head temp reaches overheat and then it shorts to ground which causes the piezo tweeter in your harness to be grounded ( purple wire on the other side side is 12v switched on) and sound off. Pulling the heads or using a snake light is the best way to see if the pistons are washing funny. Water can get in under the cowel base gasket as well as the rear divider gasket also. I believe the motor mainly will not rpm well if its leaking water. The bottom end problem is likely another issue. Probably electrical or a sticking injector. I think you have around a 1994 block so your componants may be showing some age. A bad ground can act like that as well. Lots of things it could be.