Question about Ford Escort

3 Answers

Car is showing the following 3 codes P1506, P0420, P0171 and it is going into open loop randomly at idle for no apparent reason. Would like to know what to replace to correct this issue.

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  • INXbabe Mar 11, 2011

    Will this cause the idle to run open loop randomly?

  • INXbabe Mar 11, 2011

    Will any of these problems cause the idle to run open loop randomly during idling?

  • INXbabe Mar 11, 2011

    Will either of these problems cause the sytem to run open loop randomly during idling?

  • INXbabe Mar 11, 2011

    We would like to get another opinion. We checked for vacuum leaks and replaced the IAC valve. We are still having the same problem with it going into open loop and running rough and getting the code P1506. He is considering if we need to change ECU. The short term fuel trim is right around 40-42% positive in case this plays a role in the problem.

  • INXbabe Mar 11, 2011

    We have already replaced the idle speed control as well as checked for vacuum leaks and the problem is still occurring. The engine runs ok until it goes into open loop at idle. It starts idling extremely rough and sometimes dies. Then it goes into closed loop and runs fine then. We have also changed the fuel filter as well as the mass air flow sensor and the upstream 02 sensor.

  • INXbabe Mar 11, 2011

    Ok he has changed the idle and rechecked it without driving it and the codes came back, but he is going to take it for 30 min right now and drive it.

  • INXbabe Mar 12, 2011

    After installing IAC drove car for 30 plus min. under varying conditions. Check engine light back on and has two pending codes po171 and p1506

  • INXbabe Mar 12, 2011

    This is for a 2001 Ford Escort it has approximately 140,000 miles. We still had the code after driving for 30 min but he did disconnect the vacuum hose from PCV valve and plugged it and it seemed to fix the problem. He then plugged the vacuum hose better and drive it for 30 min and experienced no codes and it drove fine. Would this confirm a vacuum leak? We have used the carborator cleaner on all hoses and connections and noticed no differences or indications of a leak. We did the intake as well.

  • INXbabe Mar 12, 2011

    This is for a 2001 Ford Escort it has approximately 140,000 miles. We still had the code after driving for 30 min but he did disconnect the vacuum hose from PCV valve and plugged it and it seemed to fix the problem. He then plugged the vacuum hose better and drive it for 30 min and experienced no codes and it drove fine. Would this confirm a vacuum leak? We have used the carborator cleaner on all hoses and connections and noticed no differences or indications of a leak. We did the intake as well. Hide Comments

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  • Ford Master
  • 1,940 Answers

P1506 - Idle Air Control Overspeed Error

  1. This could mean your Idle Air Control Valve is faulty, or it could be as simple as a vacuum leak caused by a bad gas cap. You need to remove the oil and carbon deposits from the air passage to the IAC, and from the IAC.
  2. Use a toothbrush and carb/throttle body cleaner to clean those passages. You can just spray cleaner, let it soak, to clean the throttle body bore and throttle plate. Cleaning the IAC is worth a shot since it is easy to remove and install. Be sure to disconnect your negative battery cable (before IAC removal is best) for at least 10 minutes so that your PCM will reset.
  3. If you are having idle problems even after you clean the IAC passages, and IAC, replace the IAC valve. If it is not the IAC, check for vacuum leaks. Check the length of the vacuum hoses and inspect for cracks/holes. Especially check the PCV valve/hose. Basically unmetered air is coming in and the IAC can not compensate for it.

P0420 - Catalyst System Efficiency Below Threshold (Bank 1)
The PO420 code certainly indicates your catalytic converter performance has dropped off, or your Heated Oxygen Sensor, after the Catalytic Converter, is faulty.

P0171 - System Too Lean (Bank 1)
This could mean the Mass Air Flow sensor is under measuring air flow, or you have a stuck open PCV valve or collapsed PCV valve hose, leaking air into the intake. This is more than likely the result of a stuck PCV valve, but could also mean you have a bad MAF and not that there is anything actually wrong with your cats. You should first replace your PCV Valve, then try cleaning the MAF or replacing the MAF, then reset the ECU, drive it and see if either code returns.

I would replace the Oxygen Sensor's and PCV Valve and PCV Valve hose, reset the computer's codes and see if they come back.

Posted on Mar 12, 2011

  • Jeremy Moore
    Jeremy Moore Mar 12, 2011

    Yes, it sounds like your PCV valve hose may have been leaking. Replace the hose and you should be fine.

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  • Ford Master
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P1506 FORD - Idle Air Control Over Speed Error, In plain English this means the computer control module (known as the PCM) can't control the idle speed.

Possible causes are a defective automatic Idle speed control valve (see picture below) or intake manifold is leaking or vacuum hoses are disconnected or leaking, repair this 1st before addressing the other fault codes of P0420 and P0171, the excess air in the system is very likely triggering those code To check for vacuum leaks the easiest thing to do is spray carburetor cleaner around the intake area of the engine, if you hit a vacuum leak the engine idle will change dramatically, zero in on that area to determine what is leaking, a hose or a gasket.

P0420 - Catalyst System Efficiency Below Threshold

P0171 FORD - Fuel Injection System Too Lean

Posted on Mar 11, 2011

  • 4 more comments 
  • yadayada
    yadayada Mar 11, 2011

    Once you have repaired the idle issue clear the system codes by using a scanner or disconnecting the battery NEGATIVE cable for 5 minutes, then drive for at least 30 minutes under varying conditions to see if codes return with a resulting Check engine light..

  • yadayada
    yadayada Mar 11, 2011

    Open loop is caused by the fact that the systems computer (PCM) can't control the mixture, this is related to the idle problem

  • yadayada
    yadayada Mar 11, 2011

    My experience? 25 years as a Ford dealer electronic engine control techincian. I hold a Ford master mechanic certification in this type of work.

  • yadayada
    yadayada Mar 11, 2011

    Is the engine idle speed normal?

  • yadayada
    yadayada Mar 12, 2011

    By the way what engine do you have in this truck??

    How many miles on the truck?

  • yadayada
    yadayada Mar 12, 2011

    I still think you have a vacuum leak,

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  • Ford Master
  • 19,396 Answers

Hi.

The codes mean:
P1506 :idle air control overspeed error.
P0171 :system too lean - bank 1.
P0420 :catalyst system efficiency below normal.

You probably have a vacuum leak. This can give the three DTC (trouble codes). The vacuum system is tested using a gauge like this: Vacuum Gauge, Fuel Tester in the vacuum line, while spraying carb cleaner on the vacuum hoses. Sometimes it is possible to spot a disconnected hose or an hissing leak at a glance. Sometimes you need to use the gauge.

If there is no problem with vacuum system you may have a defective idle air control system. Check IAC valve and PCV valve.

Regards.

Ginko.

Posted on Mar 11, 2011

  • Ginko
    Ginko Mar 11, 2011

    Hi.

    Re:Will either of these problems cause the sytem to run open loop randomly during idling?

    Yes. The MAF sensor and IAT values are used by the PCM to determine when to open the IAC valve. That can cause open loop
    An open vacuum hose can do pretty much the same.
    A faulty IAC valve can also give same code.

    Test vacuum first, and clean MAF (or MAP) sensor.

    PS:this is email support, allow some times for answering.

    Regards.

    Ginko.

  • Ginko
    Ginko Mar 11, 2011

    I mean, the most common reason for P1506 is a stuck IAC motor. The valve stays stuck open, the mixture is lean, and cat system efficiency is affected, hence the three codes.

    Before replacing the IAC, located in the throttle body, check the rest. In some case an open vacuum can cause the same codes. Sensors and intake problem giving the three codes are rather uncommon, but give it a check, just in case.

    I hope this makes things clearer.

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Keeps throwing up trouble codes p1506,p1151,p0302,p0171


Definition of Diagnostic Trouble Code P1506 Audi: Closed Throttle Position Switch Does Not Open/Short to Ground BMW: Idle-Speed Control Valve Opening Solenoid Control Circuit Signal High Ford: Idle Air Control Overspeed Error (see P0507) Jaguar: Idle Air Control System RPM Lower Than Expected - B Bank Kia: IAC Valve Opening Coil Voltage High Lincoln: Idle Air Control Overspeed Error (see P0507) Mazda: Idle Air Control Overspeed Error Mercury: Idle Air Control Overspeed Error (see P0507) Porsche: Throttle Jacking Unit Lower Mechanical Stop, Signal Implausible Volkswagen: Closed Throttle Position Switch Does Not Open/Short to Ground Volvo: IAC Valve Opening Signal
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Definition of Diagnostic Trouble Code P1151 Audi: Bank1, Long Term Fuel Trim, Range 1 Leanness Lower Limit Exceeded BMW: Oxygen Sensor Heater Circuit Signal Intermittent (Bank 2 Sensor 1) Ford: Lack Of Heated Oxygen Sensor Bank 2 Sensor 1 Switches - Sensor Indicates Lean Jaguar: Lack of H02S-21 switch, sensor indicates lean Land Rover: Lambda control limit bank 2.Implausible signal/condition Lincoln: Lack Of Heated Oxygen Sensor Bank 2 Sensor 1 Switches - Sensor Indicates Lean Mazda: Lack Of Heated Oxygen Sensor Bank 2 Sensor 1 Switches - Sensor Indicates Lean Mercury: Lack Of Heated Oxygen Sensor Bank 2 Sensor 1 Switches - Sensor Indicates Lean Subaru: HO2S-12 Heater Circuit High Input Toyota: Coolant Path Clog Up for Coolant Heat Storage System Volkswagen: Bank1, Long Term Fuel Trim, Range 1 Leanness Lower Limit Exceeded
------------
Definition of Diagnostic Trouble Code P0302 Category: Powertrain Definition: Cylinder 2 Misfire DetectedNote: This definition of P0302 is applied to all manufacturers
--------------------------
Definition of Diagnostic Trouble Code P0171 Category: Powertrain Definition: System Too Lean Bank 1Note: This definition of P0171 is applied to all manufacturers

Jun 17, 2015 | Cars & Trucks

1 Answer

P0420 p1399


99 civic? ever tune it up, or run the cam belt fore ever?
you do now, ignoring the bent, ends in bent valves, right?

which engine option, cylinder count and displacment. USA 1.6L? I-4?

misfiring. ever tune it up this decade? or 60k miles? with cam belt.
1399 is misfire (let me guess, the CEL flashes )
do not skip the belt if due, or you will lunch the engine.



420 is: (ID IGNORE THIS, till the MISFIRE ENDS !!!)
Possible causes
- Three way catalyst converter Bank 1
- Exhaust tube
- Intake air leaks
- Fuel injectors may be faulty
- Fuel injector leaks
- Spark plugs may be faulty
- Improper ignition timing
- Engine Control Module (ECM)

(the bar room answer for 420 is, the CAT is weak, )
the autoshop class>? ASE.. if the cat is or was tortured (misfire)
then fix that first and pray the cat bakes dry and passes 42x codes
if bake many dry, and 420s cleared.
what happens is you overload the CAT with raw fuel, ignore it.
the CEL flashing (USA) means you are KILLING THE CAT.


now we cover, misfire
there are huge possibles.
in a big shop we connect 5 gas to tail and start there .
in a lesser shop, plenty. we check closed loop at idle
if not in closed loop at idle, we fix that first. (easy ,car is parked)
(later closed loop at 40mph light flat cruise, steady right foot) no hills.
Misfire, :
Bad engine, bent a valve> do to ignoring the belt. got vacuum bounce?
bad spark
bad injection rates, or injectors clogged ,dead or weak or leaking.

me, i watch pendings to see of P0301 , to P030x (x is cylinder num)
if the scan tools shows any misfire codes, i do a leak down
on the cylinder that misfires, 300s is random.

lots of ways, EGR stuck open
AFR runing lean, scan too sees that...
AFR stuck rich, same.
the best order is this. (no clues with extra DTCS
is:
compression test. and leak down. if smart.
spark tests.
last fueling, rates, (fails closed loop at idle spark good , engine good.
i do the the injector leak down tests. and balance,

i also do the cAT melted test. cat back pressure test
less that 2psi at 2500rpm.

Dec 31, 2013 | 1999 Honda Civic

1 Answer

P0420 p0171


P0420 (emission) possibe o2 sensor, bad catalitic converter, exhaust leak, cool temp sensor, misfire etc...P0171 = too lean (not get enough fuel) poss cause air flow sensor which is normally on the air intake tube this can also cause the other fault. You first need to check the clamps are tight on the air intake tube yu replaced. then spray aerostart around intake tube & listen for change of revs. also listen for any sucking noise around motor (Vacume leak) if think detected spray aerostart around that area to see if revs change.

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1 Answer

P1506, p0171, p0174


is this a ford ? . try cleaning the iac its on the top of the engine and easy to get to .and let me know how it works

Feb 12, 2012 | Cars & Trucks

1 Answer

I have 8 throuble codes p0743,p1537,p1504,p0133,p0420,p0113,p0122,p1506,please help i don't know what to do to windstar 98 3.8


P1537

Intake Manifold Runner Control Stuck Open


P1504

Intake Air Control circuit malfunction


P1506

Idle Air Control Over Speed Error


P0112 Intake Air Temperature Circuit Low Input


P0113 Intake Air Temperature Circuit High Input


P0133 02 Sensor Circuit Slow Response (Bank 1 Sensor 1)


P0420 Catalyst System Efficiency Below Threshold (Bank 1)


P0743 Torque Converter Clutch Circuit Electrical



I hate to hear you are havine so much trouble. These are a basic descrition of each of the codes.


If each of these codes are active, i would imagine you windstar isn

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1 Answer

I have a 1997 Ford F-150. It didn't pass emissions. The Codes that came up are as follows, P1506,P0171,P0430,P0174. And comments, P0430Catalyst System Efficiency Below Threshold( Bank 2 ), and...


The p1506 is the Idle speed control Solenoid making the engine overspeed at idle. This is a small air regulating solenoid which fits into a shallow well on the intake manifold. Take it out and clean with WD40 and then try it, it is probably gummed up.

The p430 can be a worn out catalytic converter. The can be purchased new in the aftermarket or bought used at a Salvage yard. Car-parts.com will be a good place to try. Or go new with an aftermarket unit.

The 0171 and 0174 are lean codes. Check your intake manifold for leaks or when you fix the Air control solenoid I mentioned, these problems may go away. If not use a water mist around the engine seams when the engine is running to pinpoint leaks. The rpm will change.

The price of the catalytics has come down, and used parts will work too. Hope my solutions get you going for less than the price quotes.

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Code P1506, 2002 ford taurus wagpn


P1506 Idle Air Control
Overspeed Error

IAC Valve--Bad
Vacuum Leaks
IAC Stuck Open
Failed EAVP System

Disconnect the valve--if little
or no change in RPM,then
Valve is stuck or bad

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1 Answer

My 2001 toy,corolla showed a code of po171 so i changed the oxygen sensor then showed po300 , the car hesitate on excelleration but if you back up a little on the throttle it runs fine like the cat is...


P0171 is a lean code. Most common cause for this is a vacuum leak. The cat would throw a P0420 code. Don't mess with the cat. The P0300 code is a random misfire code. Look for a vacuum leak first.

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2 Answers

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Has he chkd for a throttle positio sensor or a defective mass air flowf sensor?Is there a loss os power when it is running?

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