How to fine tune TPI on 94 Mariner EFI 2.6l

[Vic]

The book says that if the motor appears to run too lean or rich the TPI can be adjusted. I do not have the harness to use with a multimeter. I need to know which direction is lean or rich clockwise or counter.


Thanks,
Vic

[THEFERMANATOR]

I'm assuming you mean that you have a 2.5L, 2.6L is YAMAHA or OMC. You can use a multi-meter that has 1 inch test probes on it and backprobe the plug to find the voltage of it. It should be .25 volts with the throttle closed and the tan/black wire on the port cylinder head disconnected. From the starboard side of the engine looking at the TPS clockwise will lean it out and counter clockwise will richen it. I can tell you from experience though that this adjustment is EXTREMELY touchy and requires a meter to set it. You don't have to have the test harness to do it though.

[Vic]

Thanks Thefermanator, I really appreciate it. I could do the whole sinc and link except for this TPI thing. Now I know whats up. Your the man.

Vic

[THEFERMANATOR]

I just went and rechecked and it is the blue wire and tan wire in the TPS that are used for the voltage reading. Disconnect the port head sensor(the one with 2 wires), backprobe the blue and tan wires with a good voltmeter set down to read less than a volt accurately, turn the key on but don't start it, adjust the sensor to .25 volts optimum(.2-.3 is acceptable range, but .24-.26 is best for a baseline), tighten it down and re-check then button it back up and run it. You may need to make some small adjustements to it to fine tune the idle mixture, but ALWAYS do it with a meter hooked up as you will see how touchy the adjustment is.

[Vic]

Thanks TheFermanator, I had Phatdaddy come by with his voltmeter. That thing is touchy. We got the base line set, but no matter where we set it, we can only get 5.25 volts at WOT. The book says it should have approx 7.46 I wonder if the TPI is bad?

[THEFERMANATOR]

You did disconnect the port head temp sensor correct? If not that will throw the adjustment WAY off and make the TPS test bad. Also make certain the throttle is going full open. The link and sync is pretty critical to get them to work right.

[Vic]

No, I didnt print your instructions so I went by the manual I had handy that said blue/tan lead wire. Sorry I'll recheck it. I did see those black/tan wires coming out of the port side. You think I should disconnect both blue/tan and black/tan maybe?

[THEFERMANATOR]

The blue and the tan wires in the TPS are the ones you measure to get your reading. The port side sensor should have 2 leads coming out that are tan with a black stripe on them. Disconnect both of them and re-check your adjustment.

[Vic]

Thanks again THEFERMANATOR, Got the correct leads disconnected this time and I got it set to .25 on the money. The wide open throttle is 6.25 definetly runs better at this setting.