idle and mpg problems

[mitsumotors]

just changed the O2 sensor, I don't know what my ambient temp is(or really what that means at all) when i checked the TPS by backprobing i did it with the ignition on but engine off, and i checked input and output voltage and got a ratio of about 17% with the TB closed all the way. is that the right way to do it?

 

[Ecomike]

just changed the O2 sensor, I don't know what my ambient temp is(or really what that means at all) when i checked the TPS by backprobing i did it with the ignition on but engine off, and i checked input and output voltage and got a ratio of about 17% with the TB closed all the way. is that the right way to do it?

Ambient, is the current outdoor air temperature. What is the high and low ambient temperature when you drive.

Have you verified that the new O2 sensor and O2 sensor heater, O2 sensor heater relay ....are working?

have you tested both TPS sensor grounds, both sides of the TPS sensor, and the O2 sensor ground?

Sounds like you checked the TPS on the ECU side only, 17% at idle or about .73 volts, but you need to check the wide open throttle and idle voltages on the other side of the TPS, they should be the reverse of the ECU side voltages for year 87 to 90. You do have an automatic transmission right?

 

[mitsumotors]

nope, 5speed

 

[Ecomike]

nope, 5speed

Sorry,

My mistake. The auto trany version has a dual sided single part TPS. Yours is much simpler. Sounds like your TPS is OK. I'd focus on the O2 sensor wires....as I mentioned below since the O2 sensor is already new.

On the low power, check the fuel pressure and pressure regulator. Also check the distributor location. If it is off by one tooth the computer will compensate but it will have little power. This a common problem, seems to be an art stabbing that guy into the right spot. Lots of good threads here on installing the distributor in the sweet spot.

And yes, high idle eats fuel. Sounds like you nearly have the MPG problem solved already, just need to solve the low power problem. If it is not the cam, it really could be the distributor off by one tooth on th cam gear.

 

[mitsumotors]

thanks