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Discussion Starter · #1 ·
i had a high idle problem, 86 glh would ide between 1500 and 2000. i diagnosed my tps source and signal were backwards on the harness that i made, so i changes that. now my car has codes 22 and 24, coolant temperature sensor and throttle position sensor out of limits.... im confused haha

any ideas?
 

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My guess is the wiring is not correct.
The TPS code will only set if the controller see's very high or very low voltage on the signal line.
I am walking out the door so I will have to get back to you later with the wiring.
 

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Dang, im not by my factory service manuals, but there is a correlation between those two sensors...on the same circuit? Wish i could recall. I think they both share a common 5v right?
 

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For the idle speed to be high your issue is related to...
Vacuum Leak
Base Idle Incorrect
Throttle Sticking
TPS Voltage High(above 1 volt at closed throttle)
AIS Circuit
 

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Discussion Starter · #6 ·
Could high voltage at tpa be caused by crap parts? What can cause that because my car has 1.5v....
 

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Usually TPS voltage being high is caused by the throttle plate being opened to far.
If you remove the TPS from the TB but leave the wiring connected what is the voltage reading?
 

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Discussion Starter · #9 ·
The signal return was getting 5v and the signal was reading 3v, i switched them around correctly and it is back to normal... i made a new tp/ ais harness from scratch and had two wires mixed up lol i feel dumb

Now, do you know what fixes the rough idle at cold start up? The car has a 3 wire o2 but i dont think the heater is hooked up... would that help? And how/where do i hook that up to work correctly?
 

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Never feel dumb, you learned something.
On cold start you are in open loop operation which is a fixed parameter mode with the O2 being ignored until temp is at a certain point(O2 and Coolant) and a set amount of time has passed.
Depending on the ambient temp cold start is a richer condition than closed loop operation and more fuel is needed for a cold engine and cold ambient temps.
Any basic condition with fuel, ignition, engine mechanical will create your problem.
 

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Discussion Starter · #11 ·
What i notice during the rough idle event is the o2 switches every two or three seconds.... i know these cars switch slow anyways but it seems to happen together...
 

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Back in the earlier days the O2 sensors were not heated and at idle and low rpm conditions exhaust gas temp would decrease and the O2 would cool causing the car to go back into open loop.
This was bad for emissions, fuel economy and shortened the life of the O2 sensor.
The heater circuit was added to keep the O2 sensor hot at all times to eliminate the above problems.
The heater circuit has no bearing on how the O2 reacts to air/fuel changes.
Problems can arise if the heater circuit is shorted.
On the 3 wire the O2 uses an existing body ground for the sensor itself while the other 2 wires are for the heater + and heater -.
The only difference with a 4 wire is the O2 will have its own dedicated ground.

When in closed loop the O2 produces a voltage thru a chemical reaction from 1-9 volts.
.450 volts is middle ground or 14.7/1 air fuel ratio which the controller is always trying to maintain in closed loop operation.
If O2 voltage drops below .450 volts the controller see's this a lean and slightly increases injector pulse width to compensate, when the voltage goes above .450 volts the controller see's this as rich and decreases pulse width, the crossing above/below .450 volts goes on constantly as fuel corrections are made.
Preferably you want crosscounts to be in the .250-.750 range.
If the voltages are going to the far ends of the scale it is beacuse there is an underlying cause making the car too rich or lean or a faulty O2 sensor.
 
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