Question about 1994 Toyota Pickup

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Idle speed When I apply pressure to my brakes will running the a/c the engine begins to idle up and down

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Check your anti freeze'rs levels.. i had the same problem

Posted on Jul 13, 2008

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This is because the computer compensates idle for when the A/C compressor is on or off. When the A/C compressor kicks in the computer will increase the engine idle to compensate for the drag in from the compressor. When the A/C is off it will decrease the idle to try and maintain a steady idle. If it is causing a high surge when the brakes are on it may be the IAC valve. If it is just slight it shouldnt be anything to worry about.

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Posted on Jun 23, 2008

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How long is complete drive cycle for a 98 chevy blazer s-10 4.3


what do you mean by complete drive cycle as it is unknown terminology

Nov 18, 2017 | Cars & Trucks

1 Answer

We just got a 2004 Chevy Express. When you start it and put it in gear, it dies. The battery appears dead and you can jump start it.


IAC - idle air control problem possibly .( You can drive it if you use your left foot to brake but keep the gas pedal down to keep the RPMs up.) Wouldn't be a fuel filter , if fuel filter was clogged partly it would idle ,but would lack power ,low fuel pressure at higher speed's . Do you know what IAC valve is ,an how it works ?
Idle Air Control Valve
Or maybe the EGR valve pintle is covered with carbon an sticking open .
Or possibly a dirty or bad MAF sensor - mass air flow sensor - the PCM - engine computer needs info from this sensor so it know's how much fuel to feed the engine .
Hooking up a professional type scan tool to view engine sensor data cut's down on guessing as too what the problem is .

007 Idle Speed Problems Scan Data for Idle

Nov 09, 2017 | Cars & Trucks

1 Answer

Engine idle very lumpy and wanting to stall on gear down shift. Sometimes poor on starting until fuel gets through then car runs well but very smelly.


SYMPTOM 1: ROUGH IDLE IN THE COLD

The engine will not idle smoothly, or it stalls during idle when the engine is cold. When the engine is cold and you take your foot off the gas pedal, the engine runs very rough and may even stall. When you run the engine at higher speeds, it seems to run fine, or at least it runs more smoothly.
Possible causes:
  1. If you have a carburetor, you may have a bad accelerator pump or power circuit.
    The Fix: Replace accelerator pump or replace the carburetor.
  2. There may be a vacuum leak.
    The Fix: Check and replace the vacuum lines as required.
  3. There may be some type of ignition problem.
    The Fix: Check and replace the distributor cap, rotor, ignition wires, and spark plugs.
  4. The ignition timing may be set wrong.
    The Fix: Adjust the ignition timing.
  5. There may be a fault in the computerized engine control system.
    The Fix: Check engine control systems with a scan tool. Test the circuits and repair or replace components as required.
  1. The EGR valve may be bad.
    The Fix: Replace the EGR valve.
  2. The engine may have mechanical problems.
    The Fix: Check the compression to determine the engine's condition.
  3. Idle speed is set incorrectly.
    The Fix: Set idle speed to the car's original settings.
  4. The fuel injectors may be dirty.
    The Fix: Clean or replace the fuel injectors.

SYMPTOM 2: ROUGH IDLE WITH WARM ENGINE

The engine will not idle smoothly, or it stalls during idle when the engine is warm. When the engine is warm or hot and you take your foot off the gas pedal, the engine runs very rough and may even stall. When you run the engine at higher speeds, it seems to run fine.
Possible causes:
  1. If you have a carburetor, you may have a bad accelerator pump or power circuit.
    The Fix: Replace accelerator pump or replace the carburetor.
  2. There may be a vacuum leak.
    The Fix: Check and replace vacuum lines as required.
  3. The fuel pressure regulator may be operating at too low a pressure.
    The Fix: Check the fuel pressure with a fuel pressure gauge. Replace fuel pressure regulator. (This is not really a do-it-yourself kind of job.)
  4. Idle speed set incorrectly.
    The Fix: Set idle speed to specs.
  5. There may be some type of ignition problem.
    The Fix: Check and replace distributor cap, rotor, ignition wires and spark plugs.
  6. There may be a fault in the computerized engine control system.
    The Fix: Check engine control systems with a scan tool. Test circuits and repair or replace components as required. (This is not really a do-it-yourself kind of job.)
  7. The EGR valve may be bad.
    The Fix: Replace EGR valve.
  1. The engine may have mechanical problems.
    The Fix: Check compression to determine engine condition.
  2. The fuel injectors may be dirty.
    The Fix: Clean or replace fuel injectors.

SYMPTOM 3: FAST IDLING

The engine idles too fast. After the engine has run long enough to become warm, the idle speed does not come down to normal. You really notice it when you come to a stop and must have to push ******* the brake pedal to keep the car from moving.
Possible causes:
  1. If you have a carburetor, you may have a bad accelerator pump or power circuit.
    The Fix: Replace the accelerator pump or replace the carburetor.
  2. The engine may be overheating.
    The Fix: Check and repair the cooling system.
  3. The fuel pressure regulator may be operating at too low a pressure.
    The Fix: Check fuel pressure with a fuel pressure gauge. Replace fuel pressure regulator. (This is not really a do-it-yourself kind of job.)
  1. The ignition timing may be set wrong.
    The Fix: Adjust the ignition timing.
  2. There may be some type of ignition problem.
    The Fix: Check and replace the distributor cap, rotor, ignition wires and spark plugs.
  3. There may be a fault in the computerized engine control system.
    The Fix: Check the engine control systems with a scan tool. Test the circuits and repair or replace the components as required.
  4. There may be a vacuum leak.
    The Fix: Check and replace vacuum lines as required.
  5. You have a bad idle speed control unit.
    The Fix: Replace the idle speed control unit.
  6. The alternator may not be working properly.
    The Fix: Replace the alternator.

SYMPTOM 4: STALLING UPON STOPPING

Car stalls when stopped quickly. You are driving along and everything is just fine ... until you let off the gas pedal and apply the brakes. The engine starts shaking and may even stall. Not a good thing to happen because you lose power steering when the engine dies and could risk an accident.
Possible causes:
  1. There may be a serious vacuum leak.
    The Fix: Check and replace the vacuum lines as required.
  2. There may be a fault in the computerized engine control system.
    The Fix: Check the engine control systems with a scan tool. Test the circuits and repair or replace the components as required. (This is not really a do-it-yourself kind of job.)
  3. Broken linkage.
    The Fix: Repair or replace the linkage as required.
Idling issues can be very frustrating, but with some patient troubleshooting, you'll have a real chance at figuring it out. Remember to always check your engine idle with the air conditioning and defroster turned off, as both of these systems are designed to change the idle when they are on due to the air conditioning system's demands on the engine.

Aug 25, 2017 | Cars & Trucks

1 Answer

2.7 s type brakes not working as they should they are ok when you start breaking but when you are down to about 10mph the pedal becomes very hard to push and the car trys to roll on ?


It is possible the problem is ABS related but could equally be a problem with the vacuum servo or brake booster or the "supply" of vacuum.

Certainly best practice would be to begin by ensuring the brakes at each wheel are in good order.

Test the brake servo by pressing the brake pedal vigorously several times while stationary with the engine off. The pedal should then feel higher than usual and rock-hard.
Apply the footbrake with a moderate force and start the engine without using the accelerator pedal, if possible. The brake pedal should be felt to pull itself down under your foot immediately the engine starts and stop pulling down in just two or three seconds, maybe just a second or two more if it is a diesel model.

Release the brake, allow the engine to idle for a few seconds longer and switch off. Listen carefully in the resulting silence for the sound of air leaking. This might have to be repeated several times in order to listen under the dash and in the engine compartment around the brake booster and vacuum lines. A short piece of garden hose used as a listening tube can be useful.

Once a servo has been charged with vacuum, in the absence of leaks, it should remain charged for a long time if the brake is not used - certainly hours but often months or even years is not unusual. Aplly a moderate pressure to the brake pedal and a shhhhh... sound should be heard that lasts about a second and then stops. Increase the pedal pressure and another shhhh sound and stop.

If all tests ok you can be reasonably confident the brake booster and vacuum lines are in order though it is still possible the vacuum supply is insufficient for sustained braking. A road test on a clear and safe downhill route will determine if this is so. Make a rapid series of brief brake applications at a constant speed of around 30mph and the braking effort and the feel of the pedal should remain consistent and if it does not it indicates restricted supply pipes or hoses, poor engine tune, incorrect idle speed (petrol models) or a worn or inefficient vacuum pump if it is a diesel.

Jul 23, 2016 | 2006 Jaguar S-Type 2.7

1 Answer

I have a 90 chev blazer that runs rough when i apply the brake ,it also has a high idle and runs rich .?


I would look at the vacuum booster control unit .
This is the power assiest for the brakes it runs off the main engine vacuum,
If its leaking inturnailly you would lose engine vacuum that would make it run rough when you hit the brakes .
Also if the check valve inside of this unit were stuck it could cause a vary high idle
Try hitting the brake pedel when its idleing high in park and see what effict it has on the engine speed .
If it changes this is for sure your problem.

Mar 21, 2015 | Chevrolet Blazer Cars & Trucks

1 Answer

1990 Isuzu pickup turns off at stop sign


If this is a petrol engine have a look at the brake booster leaking vacuum and running the engine too lean to idle. Test by allowing to idle with out your foot on the brake If applying brake pressure shuts the engine down ,replace the brake booster..

Jan 24, 2015 | 1990 Isuzu Pickup

1 Answer

Stalling troubleshooting


run fault codes to check for electronic problems (TCM). If this problem only happens when the foot brakes are applied check for brake booster vacuum problem. Remove vacuum line and blank off and apply the brakes to see if the engine stalls at idle.

Jul 22, 2014 | Ford F-150 Cars & Trucks

1 Answer

Is it modulator valve, or other?


The vac modulator only assists the transmission in knowing when to shift up.
If the engine oil pressure gauge is acting wildly, it could be the sensor or the oil pressure could really be going up and down.

Feb 23, 2014 | 1994 Ford Aerostar Extended

1 Answer

2000 mercury villager, runs a fast idle. whether cold or warm the idle remains at a high idle speed, it even pulls with the brake applied.


Could be a vac leak, or a dirty throttle body, or a faulty idle air control valve. The computer controls idle speed by regulating the amount of air into the intake. Could also be something pulling on the throttle cable such as the cruise control.

Sep 28, 2012 | 2000 Mercury Villager

1 Answer

Engine stalls when applying brakes. To prevent


You may have a dirty idle speed control valve, do the procedure below to correct this.

Get a can of intake cleaner (ABOUT $5.00) from any local auto parts store like NAPA or Carquest, do not use carburetor spray, intake cleaner only or u will damage the Teflon coating inside the throttle valve and air bypass valve, it is made by a company called CRC, remove the air intake hose to the engine, hold the idle high so the engine won't stall, then spray the can of cleaner into the intake while keeping the engine running, use at least 1/2 the can, shut down the engine and disconnect the battery for 5 minutes, then restart and complete a number of mixed driving cycles, town, freeway, stop and go etc., after a few days the problem will go away as the system will relearn to the clean intake.

May 19, 2010 | 1995 GMC Jimmy

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