Re: 98' 150 optimax poor idle
Hey buddy it sounds like a lack of air pressure or no pressure at all. Most of the checks to theses engines can be done anyone that is mechanical. I would first start with the basics as mentioned: check spark and compression. Then I would get a fuel pressure gauge and check the fuel pressure it should be 90 psi and the Schrader valve for the fuel is located on the starboard rail for a 98. Next check the air pressure, it should be 80 psi, and the test port is on the port rail. It is important to have theses numbers but it is more important to have a 10 psi difference between the two pressures. One thing to look for when your testing the air pressure is when you bleed the pressure off of the gauge you should not get more then a teaspoon of fuel from the hose. If you find a large amount of fuel on the air side you most likely have a failed tracker valve. Keep in mind that there many be some fuel still in if from when you checked fuel pressure. After theses checks I would next check the Direct Injectors for shorts. There is a service part available that will make it very easy to test them and it is cheap. Part number is 858781A2 and if you cut the locking tabs off it slips on and off really fast. Check for a 0.3 ohms or less through the DI and then you will want to check each terminal from the DI to metal housing around the DI for short. If any of them fail theses test you will want to replace it. The older version of the DI where black and if they the rails where bumped when the hood was installed and could be damaged. The part itself was of good design and there was never a recall but it just didnt hold up to customer abuse. The updated versions have a protective sleeve inside and are molded in a blue plastic. Good luck and if you need more info drop me a line. I love theses engines cuz there not that hard to work on and everyone is afraid to work on them. Optimax engines are just that a engine.
