Optimax 150 - Verrrry rough idle

[boktower]

2005 Mercury Optimax 150, low hours. I have completed replacing and having cleaned fuel and air injectors. New plugs. Tested air and fuel pressure, right where it should be. Engine STILL barely idles and will shut down (very rough idle). Revs up fine. I was told by a mobile mechanic that I have fuel squirting out my top schrader valve, I do. Releases a small amount of fuel when releasing pressure on the schrader valve after idling. The "lower" Schrader valve only releases air when depressed. I am told that fuel squirting from the top valve is "no good". I checked my fueld pressure regulator diaphragm, looks OK. Is this a function of a faulty diaphragm in the fuel pressure regulator or something else ? OR, is fuel squirting out the top schrader valve normal ?

 

[BrettNC]

Normal when the center valve core is depressed. Not normal if it is constantly leaking out of the valve.

 

[vroom ZOOM]

I won't be able to pinpoint your problem exactly, but there are a couple if issues that would cause the problem you are having. First, could you please share your air and fuel pressure readings?

One common cause of an opti running like GaRBagE is a bad battery. No kidding. You rev it up and it starts to charge, which increases the voltage to the ECM, and it will fire normally then. Mine does the same darn thing. Opti needs a big battery. If you run it too long with a bad battery you could screw up the ecm which would cause misfires. You can be chasing all sorts of problems, but low voltage and dirty contacts will drive you nuts. Secondly, the TPS sometimes gives trouble on these, which throws the timing out of wack at idle and it stalls. For some reason these fail near idle. Also, try a cylinder drop test by disconnecting each INJECTOR wire (not plug wire) momentarily while the engine is running. if you get no change on the cyl where you unplug the injector, you have trouble there. The ignition coils like to fail on some of the earlier optis, although that was mostly an 07-08 problem. I would suggest getting a computer on it to see what those sensors are reading, the voltage the ecm is seeing, and the TPS reading.