Question about 2001 Mercury Grand Marquis

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How to test a BPA-ISC valve to see if it working properly? Car is idling poorly and stalling. The connector is reading 11.85 volts. Chilton's says it should be 10.5 volts. Valve does not seem to be moving when ignition is turned on.

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Posted on Jan 02, 2017

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SOURCE: 1994 Topaz engine stalling

Normally this kind of a problem is a fuel block...there so many other ways to block...other than the filter

PLEASE don't forget to RATE ME (FIXYA) for my help..........

Posted on Aug 15, 2008

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SOURCE: cannot find idle air control valve

3.0 and 3.8 engines are next to the throttle body [throttle cable hooks to it] and is bolted down with two 5/16 head bolts,is about three inchs long and 1 1/2 round

Posted on Jan 17, 2009

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SOURCE: Idle air control valve over speed error/Code P1506

it is a fairly easy to replace the valve and its hard to say if the valve will fix your problem without a diagnosis i hope this helps


  1. Disconnect the battery ground cable.

  1. Disconnect the idle air control valve electrical connector.

  1. Remove the two bolts and remove the Idle Air Control valve (IAC valve) and gasket.


  1. Follow the removal procedure in reverse order. CAUTION:
    • If scraping is necessary, make sure not to damage the idle air control valve or the throttle body gasket surfaces or drop the gasket material into the throttle body.
    • The idle air control valve has a sludge resistant design andmust not be cleaned, or damage to the anti-sludge coating may result.

Posted on May 27, 2009

SOURCE: 1999 tracer with an engine idle that increases and

Other than the idle control/throttle sensor the other items will not usually cause bucking or change of idle. After you drive awhile from a cold start the coolant temp sensor comes into play,then the EGR valve if vacuum is involved under load. So I quess your mechanic missed monitoring the 02 sensors after testing the fuel system. Hard to imagine. Have to road test hot for Egr and other drivability issues. You need a good drivability tech and always stick with best in their field. Hard to find. Have you ever gone for a drive with the person going to work on your car sitting in the pass seat. If they don't insist on that before they ever look at your veh or take your money--enough said. Did they call you to see if your happy with their performance? If not move on. MAF,AIT, most likely on idle and EGR on bucking. Quick look at 02 sensors You or they did a good job,Just didn't hit a home run,still on second base.

Posted on Sep 29, 2009

Testimonial: "i am not sure what the "MAF or AIT" are or what they do.I will replace the EGR valve.Thanks.."

  • 18 Answers

SOURCE: 2000 Mercury Cougar 2.5l V6


Posted on Feb 10, 2011

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Replaced iac valve engine will not idle

wow , no year stated. amazing....
which engine? size and gAS or diesel>?
stalls only hot?
is thermostat good and holding 180F or more???????
why gue$$ ?

Stalls have huge causes.
1: the ISC sticks is but 1 of 50 causes (have list, i pass)
misfire is the other
the EFI Tries very very hard to stop stalls, (opens ISC/IAC 100%)
if it can't. it stalls.
why did it stall, lots of ways.
Misfire from too lean or flooding.
EGR stuck open. is #1 all top DOG for stalls.
EGR can stick open, and when it does, it will stall

no the big questions, not ever answered here ever.....>>
can you save the stall with a fast right foot action.?
tad hard.
The answer here, can save tons of hard work.

and is the CEL glow key on, in the dash? Check engine light at key on
then stay out driving, NO< why not scan this car.
do not ever ignore this lamp, scan it or spend eternity fixing car.
buy a scan tool, and learn to use it.
learn how sensors. work and how they read.
learn what closed loop is. (if not in CL hot , fix that now)

if the engine drops closed loop, hot, at idle this means
fueling is out of control and idle is only a victim.
check closed loop status hot engine. and win.

here are all the steps 1 by one on a good engine.

this is just a typical 1.6L 16valve SOHC engine.
MAF based injection, here. any motor with maf , like this..

Feb 17, 2014 | Jeep Liberty Cars & Trucks

1 Answer

06 honda element dies in am replaced iacv & still does it???

hot engine or cold or both, just a clue here.
wow gue$$sing is expen$ive.
is the CEL lamp glowing ever running,, YES?< then scan it.

ok so it stalls.
after the skipped 60k mile tuneup is done
if it still stalls.
so you use the right foot action fast acting at stall...?????
and you can prevent the stall easy.
1: very easy, iSC stuck closed or throttle idle detection is bad.
2: harder to stop stall but can , EGR leaks, main EGR valve.
3: impossible. this is gross spark failure ,or loss fuel or flooding

see how far you get on my list. and post back.

first ,now how the EFI works not guessing
it tries all the time to prevent stalls if it cant prevent it, it does stall.
rule2, the ECU controls idle speeds at all times the ISC is the slave to that..... so if the ECU open the valve and the stall gets worse.
its not the ISC/ECU fault. its fueling or spark.
a lean engine stalls. if lean enough ,no ISC can stop that.
a misfiring engine stalls, too.

a tech, dont attach the ISC< no he does not
he looks at spark an fuel rates. using , a scan tool.
The ISC can not cover the bad tracks of bad fueling and spark
nor a stuck open EGR.
THE ISC is dead if the TPS is set wrong, and the ECU thinks wrongly
that you are not at idle. so the ECU cuts idle controls

I use my scan tool to watch the, for error,s DTCS,. and pending errors
and watch for closed loop at idle. hot.
if it is in close loop at idle and it stalls then the ISC is failing
if rigth foot can save it easy.
id bet the fueling and spark are bad or TPS not closed, signalling close or the EGR is stuck wide open'

btw., if eCU drop s to limphome mod (scan it) it will infact drop all ISC
idle controls..

we look for the true cause, do tests, then replace parts
never the reverse or go broke fast.

Feb 02, 2014 | Honda Element Cars & Trucks

1 Answer

Car runs rough at start up backing up

stalls. is the word
the engine stalls not car. err both.
and is what and A/T automatic,
this very low engine power.
idle control failures.
only 2 , macro reasons.
1: weak engine (50 causes)
2: ISC dead. (i didnt say bad, many reasons for ISC system to fail
one reason is #1, the ISC can not make a weak engine strong,

a weak engine, is just that , due to misfiring (gross) or way lean
one cause of 50 , is EGR stuck open,
A good tech finds out easy 1 or 2.? reason.
doing simple test. ask.

it's like a water faucet at home.
you open it (ECU) the valve, (ISC) and no flow, or weak? seen?
is it the valve bad? or the water company failure.?
we do tests. ask, if DIY person, the tests can go for hours.

Jan 10, 2014 | 1999 Toyota 4Runner

2 Answers

Suzuki verona idles up and down at stop light.

you skipped the #1 fact, hot or cold or both?
EFI runs in MODES. cold is one , hot is another.
if coolant fails to reach proper temp, the thermostat is bad.
or installed wrong.!
I'll toss dice and land on HOT.

idle controls, are out of control. for sure. if really HOT.
This car has EFI,
EFI has many jobs but one is idle control
the ECU does that. (PCM)
if idle surges, it is , then its out of control
here is a list of things( my full list exceeds 26)
1: thermostat (coolant) is bad and wont hold 180 to 200F temps.
2: ISC (idle speed controller, dirty and sticks)
3: IAC (some cars have this and it can stick open0
4: throttle cables set wrong.
5: Air leaks so large to the plenum the ISC loses control.
6: spark or cam timing why off , poor service .
there are others, but the above covers the top ones.
there are a number of simple tests to do , that solve this riddle.
a: motor good, check compresion.
b; timing of cam good and spark?
c: i then kill the iSC, if the idle dont drop to below 600rpm or stall
I know for sure you have air leaks.
the lists for finding air leaks in the induction system (intake and plenum) is huge.
Using a smoke machine takes a very skilled mechanic.
one safe way is to use a rubber tube to your ear and listen
for hissing at said parts, idling.

Aug 14, 2013 | 2004 Suzuki Verona

1 Answer

It has a hard time starting, it will start, stall, start again, stall, then when I give it a little pedal as I try to start it, it will start, once it is started it runs great. could it be the ISC motor? I...

You are in the right area. First I would check that the throttle interior along with the plate itself is spotlessly clean along with the access passages to the ISC. I would remove the ISC and ensure the the valve likewise is spotlessly clean and has good freedom of movement. Plenty of clean cloths and WD40 spray help in the clean up. Make sure the electrical connector withe ISC is clean and tight with no breaks in the loom. Test the engine when all cleaned up and if the idle is still problem then, and only then, consider changing the ISC.

Feb 09, 2011 | 1993 Cadillac DeVille

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

My idle drops everytime i come to a complete stop and even when i put it into reverse and also sometimes the car shuts down...

Idle Air Control (IAC) Valve OPERATION The ECM is programmed with specific engine speed values to respond to different engine conditions (coolant temperature, air conditioner on/off, etc.). Sensors transmit signals to the ECM which controls the flow of air through the bypass of the throttle valve and adjusts the idle speed to the specified value. Some vehicles use an Idle Speed Control (ISC) valve while others use an Air Valve (AV) or Idle Air Control (IAC) valve to control throttle body by-pass air flow. TESTING 2S-ELC Engine
  1. With the engine running and the coolant temperature below 140°F (60°C), pinch off the Air Valve hose and verify that the idle is reduced by no more than a 100 rpm.
  2. Unplug the valve wire connector and measure the coil resistance with an ohmmeter. It should be 40-60 ohms with the coolant temperature at 176°F (80°C) and the air valve closed.
  3. If not as specified, replace the valve. 3S-FE and 5S-FE Engines NOTE: The idle speed must be set correctly before testing the ISC valve.
  4. Bring the engine to normal operating temperature with transmission in N.
  5. Using a jumper wire, connect the terminals TE1 and El of the check connector (DLC 1). Fig. 1: Attach a jumper wire to the terminals TE1 and E1 in the DLC 1 89554g46.gif

  6. The engine rpm should rise to 900-1300 rpms for 5 seconds. Check that it returns to idle speed. If rpm is as specified, the valve is functioning properly.
  7. If rpm did not function as specified, stop the engine and disconnect the jumper wire.
  8. Disengauge the ISC valve connector.
  9. Using an ohmmeter, measure the resistance between the +B terminal (middle terminal) and the ISC1 - ISC2 (3S-FE) and the ISCC - ISCO (5S-FE) outer terminals. Fig. 2: Attach an ohmmeter and measure the resistance between the three terminals - 3S-FE engine 89554g49.gif
    Fig. 3: Attach an ohmmeter and measure the resistance between the three terminals - 5S-FE engine 89554g47.gif

  10. The resistance should be 16-17 ohms on the 3S-FE engine and 19.3-22.3 ohms on the 5S-FE engine.
  11. If not as specified, replace the ISC valve.
1MZ-FE Engine NOTE: The idle speed must be set correctly before testing the valve. Make sure the A/C is off during testing. Fig. 4: The IAC valve is attached to the lower portion of the throttle body 89554p46.jpg
  1. Bring the engine to normal operating temperature with transmission in N.
  2. Using a jumper wire, connect the terminals TE1 and El of the check connector (DLC 1).
  3. The engine rpm should rise to 1000 rpms for 5 seconds. Check that it returns to idle speed. If rpm is as specified, the valve is functioning properly.
  4. If rpm did not function as specified, stop the engine and disconnect the jumper wire.
  5. Disengage the ISC valve connector.
  6. Using an ohmmeter, measure the resistance between the +B terminal (middle terminal) and the RSC and RSO outer terminals. Fig. 5: Attach an ohmmeter and measure the resistance between the three terminals - 1MZ-FE engine 89554g48.gif

  7. The resistance should be 21-28.5 ohms on a hot engine.
  8. If not as specified, replace the ISC valve.
2VZ-FE and 3VZ-FE Engines
  1. Disengage the ISC valve connector.
  2. Using an ohmmeter, measure the resistance between the B1 terminal (lower middle terminal) and the S1 or S3 (lower outer terminals), and between B2 terminal (upper middle terminal) and the S2 or S4 (upper outer terminals). Fig. 6: ISC terminal identification - 2VZ-FE and 3VZ-FE engines 89554g50.gif

  3. If the resistance is not 10-30 ohms, replace the ISC valve.
  4. Apply battery voltage to terminals B1 and B2 while repeatedly grounding S1, S2, S3, S4, S1 in sequence. Check that valve moves toward the closed position. Fig. 7: Testing the IAC using battery voltage to see if the valve will close-2VZ-FE and 3VZ-FE engines 89554g51.gif

  5. Apply battery voltage to terminals B1 and B2 while repeatedly Grounding S4, S3, S2, S1, S4 in sequence. Check that valve moves toward the opened position. Fig. 8: Testing the IAC using battery voltage to open the valve - 2VZ-FE and 3VZ-FE engines 89554g52.gif

  6. If valve does not function as specified, replace the ISC valve.
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Oct 12, 2010 | 1995 Toyota Camry

2 Answers

My 1995 cougar xr7 stalls when it de-excelerates. Also fails to start after engine is shut off.



Ford doesn't use idle air bypass to regulate idle speed on its older throttle body (CFI) applications, but uses a solenoid or vacuum diaphragm instead to open the throttle linkage. Idle air bypass is used only on multipoint injection applications. On older pre-OBD II cars, codes 12, 13, 16, 17 & 19 all indicate idle speed is out of spec (too high or too low). Codes 47 and 48 indicate a fuel mixture problem which could be caused by an air leak. On OBD II vehicles (1996 & newer), codes P505 to P509 indicate a fault with the idle speed control system.

The diagnostic procedure when any of these codes are found is to turn the engine off, unplug the ISC bypass air solenoid connector, then restart the engine to see if the idle rpm drops (it should if the ISC solenoid is working). No change would indicate a problem in the motor or wiring.

The ISC solenoid can be checked by measuring its resistance. With the positive lead of a digital volt/ohm meter on the VPWR pin and the negative lead on the ISC pin, measure the resistance of the solenoid. On many applications, the spec calls for 7.0 to 13.0 ohms. If it is out of specs, the ISC solenoid is bad. Also check for shorts between both ISC solenoid terminals and the case.

If the ISC checks out okay, check for battery voltage between the ISC connector terminals while the key is on. Voltage should also vary when the engine is running. No voltage indicates a wiring or computer problem.

Jul 03, 2009 | 1997 Mercury Cougar XR7

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