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Dj
Dj, ASE Certified Technician
Category: Toyota
Satisfied Customers: 1780
Experience:  ASE Master Tech, 30+ years in automotive repair.
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I have a 1986 toyota 4Runner with a 22re engine. The problem

Customer Question

I have a 1986 toyota 4Runner with a 22re engine. The problem I'm having is the engine won't go to fast idle when cold. I've bench tested and installed checked the cold start sol. it works fine. I've also bench tested and installed checked the air flow sol. it works fine to . I've checked the cold start time switch and it works fine to. I've even made sure that all the wiring and connections for power when there should be power and everything checks fine there to. Has anybody else this problem also?
Submitted: 4 years ago.
Category: Toyota
Expert:  Dj replied 4 years ago.

Customer,

 

The cold start time switch and the cold start injector are active only when the key is in the start position. If the engine is cold enough, it squirts extra gas into the intake manifold.

 

I suggest that you check the engine coolant temp sensor. It should have:

10-20 k ohms at -4' f

4-7 k ohms at 32' f

2-3 k ohms at 68' f

 

It should have 5 volts on one pin, and about a volt or less on the other pin with the key on and the engine at operating temperature.

 

Let me know what readings you get.

 

Thank you in advance for accepting my answer. If you need more help, just ask. If you feel that my response isn't helpful, please let me know and I will release your question back into the list.

 

Dj

Customer: replied 4 years ago.
With the engine at 50 degs. I get about 5.2K ohms across the pins. With the engine at operate temp. With the key on I have the 5 volts on one pin and about a half of volt on the other.
Expert:  Dj replied 4 years ago.

Donm,


Lets check the air flow meter next. The coolant temp sensor is working.

 

From the yellow-green wire to the brown-black wire on the air flow meter, the specs are:

 

10k-20k ohms at 4'f

4k -7k ohms at 32'f

2k-3k ohms at 68'f

 

There are two vacuum switching valves on the engine. Have you done any testing on them?

 

Dj

 

 

 

Customer: replied 4 years ago.

When you say wire color yellow green where is that wire at? Is it coming from the temp. sensor to the black brown wire on the air meter? You also said there are two vacuum swithing valves on the engine? On this engine the only other one I see is the one valve for making the engine idle faster when the AC is on.

Expert:  Dj replied 4 years ago.

Donm,

 

There is a green- yellow and a yellow green on the mass air sensor.

 

Green yellow means the wire is mostly green with a yellow stripe. Y G is mostly yellow.

 

It should be the last pin on the air flow meter. It's the yellow-green wire. The one on the other end of the connector is green-yellow. Very easy to confuse. There is a yellow-blue wire next to the yellow green.

 

My book shows the fuel pressure up solenoid on the back of the engine, passenger side. It has a green wire and a white-red wire. Have you tried powering up the idle up solenoid to see if it works and picks up the engine speed?

 

Dj

Customer: replied 4 years ago.
I installed a new air flow meter on the truck thinking it was the problem. When I turn the AC on the engine won't idle up there either.
Expert:  Dj replied 4 years ago.

Donm,

 

Either the problem is:

Not getting power from the engine control unit to the idle-up solenoid because the computer thinks that it's not needed.

Getting power to the solenoid but no ground

Getting power and ground but not activating the idle-up solenoid

Activating but not letting air pass through.

 

Both the air temperature sensor in the air flow meter and the coolant temperature sensor tell the computer what the temperature is and if idle-up is needed.

 

It's a process of elimination. I always start with sensors because they fail more than anything else. But next check the solenoid by first, checking for power and ground when it's supposed to be activated.

 

Dj

 

 

Customer: replied 4 years ago.
Let me do some more checking. You mentioned the air temp sensor where is it located? Is it in side the mass air flow meter? I don't see any other sensor around the intake man. or the air plenum?
Expert:  Dj replied 4 years ago.

Donm,

 

The air temp sensor is an integral part of the mass air sensor.

 

Dj

Customer: replied 4 years ago.
I can get the idle up valve for the AC to work. Basically I had to get my AC recharged and now when I push the AC button on the motor I idles up fine for that. I checked the air temp sensor and I get between 2 to 2.5K ohm's across the sensor. You mentioned earlier about a couple of vacuum switching valves but I only see, and wired for, just one and it's for the AC to idle up the motor when it's turned on. Where is or would be the other one located? I've checked the wire harness and I don't a connector but I do have 2 wires, one is a solid yellow wire and the other is a white with red stripe wire and they both have power on them when I turn the key to ignition. The wires come out of the harness around by the AC compressor and are taped off. What did or what should these wires be doing?
Expert:  Dj replied 4 years ago.

Donm,

 

That reading would tell the computer that the temperature is about 68 degrees. Is that correct?

 

I went through the entire wiring diagram for the truck and white - red is a 12 volt wire with then key on that goes all over the engine compartment. Yellow is used on a couple of different circuits, the throttle position sensor, the alternator (sends the signal to the dash warning light), from the cruise control computer to the relay, and from the little square check connector under the hood to the computer.

 

I couldn't find anything with both the yellow wire and a white - red wire.

 

So now we know that the solenoid works and the ECU works. So it still comes down to inputs or to the ECU or a faulty ECU.

 

The thing to check now is to back probe the ECU and see if you are getting the same readings at the ECU as at the sensor. If not, there is a broken wire between the sensor and the ECU, or a bad connection at the ECU. Using the same color code of the wires, check resistance at the back of the ECU.

 

The most common cause of a problem is with the connectors at the back of the ECU. If you have to rock the connector to get it disconnected from the ECU, it's common to stretch the connectors out and cause an open circuit. I use a piece of piano wire to test the tension on the connectors. Be gentle, it's really easy to stretch out a connector with too big of a piece of wire.

 

Dj

Customer: replied 4 years ago.
Are you talking about the air temp sensor and or the mass air flow sensor and or the water temp. sensor?
Expert:  Dj replied 4 years ago.

Donm,

 

All of them. Since they all go to the ECU, it won't take too long. But it's looking like the signal from one of the temp sensors (air or coolant) may not be getting to the ECU, so the ECU doesn't turn on the idle-up solenoid.

 

Dj

Customer: replied 4 years ago.
Dj So what your are saying is the idle up sol. that works on the AC side is also the sol. that needs to turn on when the engine is cold? What make it drop down slowly when the engine is warming up? I guess I'm getting confused about how the high idle works when the engine is cold? I thought that the three things needed to let the engine go to high idle was the air temp. sensor, water temp. sensor, and the air valve? If you don't minded can you please work me through the whole process of what makes the engine go to high idle when it's cold? Or even better can you draw me a wire schmatic of how it's laid out?
Customer: replied 4 years ago.
Dj, It's getting late for me hear can we discuss this further tomorrow, If you don't mind?
Customer: replied 4 years ago.
Dj, Sorry I couldn't get back to you today but I was called away on work. Anyway were you able to come up with a wire schmatic or pin out diagram on what to check at the ECU?

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Dj
Dj
Auto Failure Analysis & Inspections
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ASE Master Tech, 30+ years in automotive repair.