4age 20v silvertop bad mpg

tristan582
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Joined: Sun Feb 02, 2014 1:52 pm

4age 20v silvertop bad mpg

Postby tristan582 » Sun Feb 02, 2014 2:08 pm

I have had this car for about six months and along with it I have been working on getting all the kinks out. I will try to be detailed as possible. Car is a 1986 Toyota Mr2. Started out as a 16v then was swapped with custom harness to run blacktop ecu on silvertop engine. The car then was railed on and threw a rod bearing according to previous owner. I picked up the complete car with everything including blown engine for 1500. Got the complete engine and tranny for 700 from a jdm place in Southern California. Thought how hard can it be. Being the ambitious 17 year old I dove in. 3 weekends later I had my 86 mr2 driving. I got a new dizzy cap and rotor, plugs, wires, fuel pump reg, retimed, all fluids flushed and changed, new o2 sensor. Has the map conversion (with a fresh map from a 92 corolla) I can see black soot coating all my plugs, o2 and when holding a rag near the tailpipe you can see it turn black. I replaced the map and that seemed to help because of a cracked vacuum line. My oil pressure sensor doesn't work. I still need to steal the old one of the blown engine. My mileage is really bad like 7mpg. I know its running rich and need/want to fix as soon as possible, because its eating me alive in gas as my DD. I heard that leaky injectors may cause this. I have a spare set that I'm thinking about swapping soon. All suggestions are really appreciated. Thanks for any and all help. :D

tristan582
Posts: 6
Joined: Sun Feb 02, 2014 1:52 pm

Re: 4age 20v silvertop bad mpg

Postby tristan582 » Wed Feb 12, 2014 4:23 pm

bump

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jondee86
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Re: 4age 20v silvertop bad mpg

Postby jondee86 » Sat Feb 15, 2014 2:27 pm

If the engine is running full rich all the time, you need to check...
1. Water temp sensor for the ECU present and working correctly.
2. MAP sensor getting a strong vacuum signal at idle.
3. MAP sensor sending the correct signal to the ECU.

Cheers... jondee86
The reasonable man adapts himself to the world; the unreasonable one
persists in trying to adapt the world to himself. Therefore, all progress
depends on the unreasonable man.

tristan582
Posts: 6
Joined: Sun Feb 02, 2014 1:52 pm

Re: 4age 20v silvertop bad mpg

Postby tristan582 » Sat Feb 15, 2014 5:02 pm

Alright so what can I use to check how much pressure is going to map sensor. I have three spare map sensors and replaced my old one. I also replaced some old vacuum lines that were cracked. Water temp sensor exchangeable with any other Toyota's like the map? Thanks for the help

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jondee86
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Checking the MAP Sensor...

Postby jondee86 » Sat Feb 15, 2014 6:18 pm

- At the MAP sensor plug and you should have 4.5 to 5.5V between pins with ignition ON.
- When you take the hose off the MAP sensor when the engine is idling, you should be
able to feel/hear manifold vacuum at the end of the hose, and the engine should
run even richer/idle worse than it usually does.
- If you hook a meter up to the pins on the sensor and read the Ohms, they should
change when you take the hose off or put it back with the engine running.

These are simple practical tests to see if your MAP sensor is working or not, and if
the circuit to the ECU is good.

Cheers... jondee86
The reasonable man adapts himself to the world; the unreasonable one
persists in trying to adapt the world to himself. Therefore, all progress
depends on the unreasonable man.

tristan582
Posts: 6
Joined: Sun Feb 02, 2014 1:52 pm

Re: 4age 20v silvertop bad mpg

Postby tristan582 » Sat Feb 15, 2014 6:19 pm

O cool. Seems easy enough. Thanks

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jondee86
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Checking the Water Temp Sensor...

Postby jondee86 » Sat Feb 15, 2014 6:35 pm

- At room temperature the water sensor should have 2 to 3 kOhms
measured at the sensor pins.
- The plug should have some small voltage between pins, maybe 2 or
3 volts when the key is ON.

Open circuit or short to ground will result in the ECU thinking the
engine is always cold, and it will always run rich.

Cheers... jondee86
The reasonable man adapts himself to the world; the unreasonable one
persists in trying to adapt the world to himself. Therefore, all progress
depends on the unreasonable man.