Question about 1991 Toyota Pickup

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Thermowax Idle-Up Valve inside Throttle Body Sticks

My 91 Toyota pickup has a problem with the thermowax idle sticks part of the way open, causing an idle there an easy fix for this? I was told I would have to replace the whole throttle body assembly.

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Posted on Jan 02, 2017

  • 314 Answers

SOURCE: Loping and high idle

You are really onto it! Either the TPS or the cable from the peddle. Do check the cable first. Frankster016

Posted on Oct 26, 2008

  • 1 Answer

SOURCE: Ls400 Throttle Body Plate

The Jam nut adjusts the throttle plate. Be careful when playing with that cos if you go out of the "range" of the accelerator position sensor the throttle will stop responding

The other (screw) is to set the maximum range of throttle movement (WOT and closed)

Posted on Dec 09, 2008

  • 140 Answers

SOURCE: 1988 nissan pickup engine rotates but does'nt start.

it sounds like the injectors are not opening up man.. replace the injectores and this should fix your problem..good luck keith....

Posted on Mar 21, 2009

  • 11 Answers

SOURCE: on a 04 camry with 2.4 ltr engine, can I replace

I think the terms "Throttle Positon Sensor", TPS and "Throttle Body" can be misleading at least in regards to the 04 Camry.

My 04 Camry gave a diagnostic reading of P2121 for my problem "Throttle PEDAL position switch D circuit". However, we changed out the complete Throttle Body/TPS (Toyota Part #22030-0H020) that did NOT fix problem.

The 04 Camry TPS Electronic Module "Throttle Positon Sensor" is factory assembled and riveted to the side of the throttle body. The only way to service/inspect it would be to cut off or drill out the rivets. Not sure you could open the darn thing if you got it off, but that seems to be the only way Toyota sells them!!

Hopefully a new Throttle PEDAL Position Sensor (Toyota Part # 78010-33010 PEDAL ASSY, ACC)
will fix it. This is located under the dash near the accelerator pedal.

So, now I would recommend FIRST to replace the "Throttle PEDAL Positon Sensor" (it is much, much cheaper) and then the Throttle Body/TPS assembly!! Unless of course, you get a diagnostic code as you did for "faulty throttle body!!

Posted on Jan 21, 2010

  • 63 Answers

SOURCE: need to know location of throttle position sensor

Not 100% sure on your exact car but nissan TPS usually are on the opposite side of the TB from the butterfly return spring.

Posted on Mar 09, 2010

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1 Answer

Code P1559?

P1559 - Throttle Body (J338): Fault in Basic Settings Possible Symptoms
  • Not known
Possible Causes
  • Idle Switch Open or Open Circuit
  • Throttle Valve sticks and won't close
  • Speed Impuls from Engine Speed Sensor (G28) recognized
Possible Solutions
  • Perform Throttle Body Adaptation

Mar 10, 2016 | 1996 Audi A4

1 Answer

How to clean the throttle body and the idle air control valve

I typically remove them to clean but they can be cleaned on the car. Get throttle body cleaner from the store and spray all over. Manually open the butterfly valve and wipe after. I would take the idle air control vavle off to clean it.

Dec 10, 2013 | 2002 Toyota Camry

1 Answer

Idle air control valve

The IAC is enclosed in the black plastic body which is attached on the side of throttle body, which cannot be opened. You can only clean the throttle body barrel from inside, and re-learn the idle speed control valve.

Jul 29, 2013 | 2007 Toyota Yaris 1.3

1 Answer

95 taurus idling too high like it is stuck wide open

Several issues can cause this problem, either singularly or in combination.. Check the throttle body for dirt and sticky carbon deposits. clean the throttle body using a spray can carburettor/choke cleaner, and with the throttle valve held open, wipe out the bore of the throttle body with a solvent soaked clean rag. Make sure the throttle valve is not sticking any where in the throttle travel between closed and open.

Next, check the idle air bypass valve that is mounted on the top of the throttle body, for dirt and carbon deposits inside that can cause the idle air bypass valve to stick in an open position. Clean the inside of the idle air bypass valve with carb cleaner.

If the ignition timing is over advanced, (Specifies timing advanced is10 degrees Before Top Dead Center, with the in-line spark out plug removed from the spout connector housing, and with the idle speed set to the idle RPM shown on the emissions sticker under the hood, with the engine fully warmed up,) use a timing light to check and set the ignition timing to specification.

The throttle position sensor must be installed on the throttle body using the required method or the idle speed will likely be excessively high. Beginning with the battery negative cable disconnected from the battery, and with the throttle position sensor removed, place the sensor in position on the throttle body with the drive tabs on the sensor placed after the drive tabs on the throttle shaft, the holding the sensor on the throttle body, rotate the sensor counter clockwise to align the mounting screw holes in the sensor and the throttle body, Insert the sensor screws into the senor screw holes, into the threaded holes in the throttle body and tighten finger tight. Carefully center the sensor on the sensor screws, then tighten the screws firmly without over tightening. Reconnect the sensor electrical harness connector.

Inspect the throttle valve idle stop screw adjustment that holds the throttle valve open slightly, to prevent the throttle valve from touching the throttle body bore surface with the throttle closed, and the accelerator pedal unpressed.

Dec 30, 2010 | 1995 Ford Taurus

1 Answer

Rough idel and no power on my 95 aspire changed plugs,plug wires,air filter,pc filter. runs great at high speed but hard to start and wont idel

Check for leaking vaccum lines from the engine intake manifold. If no leak, test the IAC motor and clean out the air bypass passages per instructions below. Let me know if this doesn't solve the problem or you have any questions.

The Idle Air Control Bypass Air (IAC BPA) valve consists of an idle air control valve and a bypass air valve. The bypass air valve functions during cold engine conditions to increase engine idle speed. It consists of a thermowax bead and a valve.
Engine coolant is directed around the thermowax, which opens and closes the valve. During cold engine operation below 140°F (60°C), the thermowax is contracted enough to allow the valve to open. As the coolant heats, the thermowax begins to expand. When the coolant reaches temperatures above 140°F (60°C), the thermowax expands and closes the valve.
The valve controls the amount of throttle valve bypass, which ensures a smooth idle under all engine operating conditions.

  1. When the engine is cold, air flows through the valve during all modes of engine operation, to maintain the factory set idle speed.

TESTING See Figures 1, 2 and 3 (if you don't have an ohmmeter, skip this test)

  1. To check the Idle Air Control (IAC) valve resistance, unplug the IAC valve connector.
  2. Connect a high impedance Digital Volt Ohmmeter (DVOM) to the terminals.
  3. Measure the resistance.
  4. The resistance should be 7.7-9.3 ohms.
  5. If the resistance does not meet specification, replace the IAC BPA assembly.

Fig. Fig. 2: Connect an ohmmeter to the IAC valve; the resistance should be 7.7-9.3 ohms

At this point, if your IAC checks good, I recommend you take out the 4 screws seen above, remove the motor, and clean out the air passages/valve with carb cleaner. Also remove the big (3 inch diameter) hose from the throttle and clean out the throttle body, if dirty.

If the IAC tests bad, go to the removal and installation directions below.

The next test requires a scanner. If you don't have a scanner, skip this test.

  1. To check the BPA valve function, remove the BPA valve from the engine.
  2. Wait until the valve reaches room temperature. When the valve is cold, blow through the air inlet and verify that air flows freely through the valve.
  3. Heat the valve with a hair dryer; the air valve should move out and block the passage.
  4. If the valve does not function as specified, replace the IAC BPA assembly.
  5. To test the solenoid, connect a scan tool to the Data Link Connector (DLC).
  6. Turn the key ON and enter the simulation test.
  7. Access the IACV Parameter Identification (PID) and turn the dial to cycle at 75 degrees.
  8. Listen for the IAC solenoid to click when using the simulation test.
  9. If the solenoid clicks it is working properly.

Fig. Fig. 3: Idle Air Control Bypass Air (IAC BPA) valve assembly components


  1. Disconnect the negative battery cable.
Never open, service or drain the radiator or cooling system when hot; serious burns can occur from the steam and hot coolant. Also, when draining engine coolant, keep in mind that cats and dogs are attracted to ethylene glycol antifreeze and could drink any that is left in an uncovered container or in puddles on the ground. This will prove fatal in sufficient quantities. Always drain coolant into a sealable container. Coolant should be reused unless it is contaminated or is several years old.
  1. Drain the coolant until it is at a level below the Idle Air Control Bypass Air (IAC BPA) valve.
The lower coolant line should be disconnected after the valve is separated from the upper intake manifold.
  1. Tag and disconnect the upper coolant hose from the valve.
  2. Unplug the valves electrical connector, then loosen the two nuts and two bolts attaching the valve to the upper intake manifold.
  3. Pull the valve from the manifold and disconnect the lower coolant line from the valve.
  4. Remove the valve and gasket from the engine.
To install:
  1. Use a scraper to clean any old gasket material from the valve mounting surface.
  2. Install a new gasket and connect the lower coolant line to the valve.
  3. Install the valve and its retainers. Tighten the nuts and bolts to 71-88 inch lbs. (8-10 Nm).
  4. Engage the valves electrical connection and the coolant hoses to the valve.
  5. Fill the cooling system and connect the negative battery cable.

Dec 05, 2010 | 1995 Ford Aspire

2 Answers

'03 Toyota Corolla 1,4 VVT-i 4ZZ engine idle rpm

Idle is factory set and cannot be adjusted, your best bet is checking for cracked hose pipework for air intake at idle,(not at problem under exceleration and driving) Any slight upset to the air /fuel ratio will be most prevelent at idle speeds.Check hoses where the meet metal flanges on manifold intakes and any sharp bends in ppipes.Good luck

Apr 05, 2010 | 2003 Toyota Corolla

2 Answers

My 2003 Ford Escapes gas pedel sticks when you try to take off.

The most common reason for this is a buildup around the butterfly valve in the throttle body. Under the hood, find the intake hose that runs from the air cleaner box to the intake of the engine. Remove the hose from the throttle body.

On the inside of the throttle body, you will see the butterfly valve which opens when you press the gas pedal. Clean the throttle body with a suitable cleaner such as Throttle Body Cleaner, which can be found at your local parts store. An old toothbrush and rags work well for cleaning the valve and behind the valve. Dry everything up and reassemble.

Other reasons could be sticking linkages at the throttle body that actuate the butterfly valve, or something as simple as your floor mat catching the pedal when depressed.

Jan 01, 2010 | 2003 Ford Escape

2 Answers

Throttle sticks at times when starting out. Hear a popping sound and throttle moves easily then

there is a throttle-stop, this prevents the throttle valve getting stuck in the bore, put simply the valve is a perfet fit and if it fully closes it is liable to get stuck in that position, so a "stop" is employed to keep the throttle just a tiny bit open, but without increasing the idle speed, it is similar to an idle-control screw. tighten this a little, so it keeps the throttle a little more open - check this diagram to find the stop adjuster screw.09aa699.png

Nov 06, 2009 | 2000 Chevrolet Silverado

1 Answer

Car runs then dies toyota

Problem may be idle control. In throttle body, butterfly valve can get gummed up and stick causing motor to start but then die. Remove air passageway from front of throttle body and spray intake cleaner or chemtool B12 inside while holding throttle open. This should clean up gummy residue and allow idle control to work properly. This works for us.

May 10, 2009 | Toyota Camry Solara Cars & Trucks

3 Answers

Car idles too high and dies

The later 80's accords have a problem with idling being to high at start up, even when the ambient air temp does not warrant it. I have had a 86 and now an 87 accord and both did that. I pretty much deal with it, being as you cant hardly replace indiv carb parts. Adjusting the idle will do nothing to stop it either. I took my 86 to a shop when I still had it and he fixed it, but I cant remember what all he did. I know he drilled a couple small holes in the choke plate. I think that the thermowax valve is bad, but again, you cannot find just a thermowax valve or anybody who knows what it is. Replacement carb in my area is about $450. Like I said, you might just have to learn to live with a high idle at start up.

Jun 30, 2008 | 1987 Honda Accord

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