Ford Explorer

Tiny
EXFORD
  • MEMBER
  • 1996 FORD EXPLORER
  • 4WD
  • AUTOMATIC
  • 242,000 MILES
My 1996 ford explorer was running pretty well then it started to die when you took your foot of the acclerator to stop We put spark plugs and wires, fuel injectors and throttle position sensor and the idle air control valve and now it will not idle right even when it starts What could have happened?
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Monday, January 3rd, 2011 AT 9:48 PM

20 Replies

Tiny
OBXAUTOMEDIC
  • EXPERT
Hello,

Ok, is engine light on? If so getting codes will greatly assist in pin pointing the problem.

Now first off did you double check the firing order, to make sure it is right.

Also did you check the connections to the parts you replaced to make sure they are tight.

Post finding.
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Monday, January 3rd, 2011 AT 11:26 PM
Tiny
EXFORD
  • MEMBER
Codes 174,171,1131,1151 checked for vacuum leaks none found. What does it mean lack of O2 switches and transitions? O2 sensors 1 on both banks has been changed so has the fuel pressure regulator, fuel
pump, EGR valve and it's sensors and tube and the Maf was cleaned.
Yesterday the engine was warm it would run smooth at idle for about ten minutes and then it would chug give a little gas it would run
smooth again. This morning when I start it would idle without some
acceleration before it would start with just a turn of the key
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Tuesday, January 4th, 2011 AT 1:12 AM
Tiny
OBXAUTOMEDIC
  • EXPERT
Ok, lack of O2 switch - with the codes you have you vehicle is running in a lean condition - With a normal running vehicle the O2 Sensors will switch from lean to rich or in other words.

When the computer receives a rich signal (high voltage) from the O2 sensor, it leans the fuel mixture to reduce the sensor's feedback voltage. When the O2 sensor reading goes lean (low voltage), the computer reverses again making the fuel mixture go rich. This constant flip-flopping back and forth of the fuel mixture occurs with different speeds depending on the fuel system.

So with your vehicle pretty much stuck in lean condition it is not switching back and forth.

I am leaning toward the MAF Failing but let me see if I can find a test proceedure for you before replacing. I will have to check my tomorrow and will get back with you. In the mean time try disconnecting the MAF and see what happens.

.
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Tuesday, January 4th, 2011 AT 4:23 AM
Tiny
EXFORD
  • MEMBER
When we tried to start it this morning it didn't want to start so my
son unplugged the MAF and it started the rpm went up and back down several times and then it smoothed out. There was no change when he plugged it back in or unplugged it with the engine running
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Tuesday, January 4th, 2011 AT 4:10 PM
Tiny
OBXAUTOMEDIC
  • EXPERT
Ok, well could have been just a dirty electrical connection and removing a reconnecting cleaned it some for better connection. See how it does and if continues you will need to replace the MAF.

The RPM flucuation was the computer setting to a default setting so the vehicle would run.

.
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Tuesday, January 4th, 2011 AT 4:19 PM
Tiny
OBXAUTOMEDIC
  • EXPERT
Also, the only testing for the MAF that I have been able to find is using an automotive Osiliscope.
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Tuesday, January 4th, 2011 AT 4:30 PM
Tiny
EXFORD
  • MEMBER
Thank you for your time and info. We were getting so frustrated because it seemed the more we fixed the worst it got.I think I understand it a little bit because it was coding off and on things were working but not to capacity and when we replaced, the new items caused it to show up the worn items.I will recommend your site
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Tuesday, January 4th, 2011 AT 11:22 PM
Tiny
OBXAUTOMEDIC
  • EXPERT
No problem, if keeps acting up just post back here in the forum and we will start again.
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Tuesday, January 4th, 2011 AT 11:32 PM
Tiny
EXFORD
  • MEMBER
The maf was replaced now it starting with the turn of the key and has plenty of power and doesn't hesitate when u stomp on it but it starts to chug in idle when the engine is warm after about 40 seconds. It doesn't do it when u first start it until it starts getting warmed up. The coupling where the two exhaust pipes come together came
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Monday, January 10th, 2011 AT 5:00 PM
Tiny
EXFORD
  • MEMBER
The maf was replaced. It is now starting with the turn of the key and it has plenty of power. It doesn't hesitate when u stomp on it but it is chugging on idle when the engine is warm after 40 seconds. It doesn't do it when u first start it until it starts to warm up. The coupling where the 2 exhaust pipes comes together came down and was wired up could that be the problem? It coded 171 & 1151.
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Monday, January 10th, 2011 AT 5:20 PM
Tiny
OBXAUTOMEDIC
  • EXPERT
Yes it could be, have it fixed and clear codes. Post results.
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Tuesday, January 11th, 2011 AT 3:10 AM
Tiny
EXFORD
  • MEMBER
I got the coupling fixed it didn't help if anything it intensified the idle problem. The guy that fixed the coupling said he thought fresh air was getting into the exhaust and messing with the O2 sensors is that possible? He was thinking the EGR tube but that was replaced in 2009 and nothing has coded about the EGR since we replaced it and all it's sensors. If there is a leak is there a way to make it show up?
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Thursday, January 20th, 2011 AT 6:09 PM
Tiny
OBXAUTOMEDIC
  • EXPERT
Ok, Yes fresh air getting into the exhaust will mess with O2 Sensors.

Finding vacuum leaks can a pain in the b_u_tt. One way I use is to purchase a can of carb cleaner. Start engine and quick sprays at vacuum connections. Then do the same at gaskets - EGR, Throttle Body, Intake etc. When engine reves you have found a leak.

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Friday, January 21st, 2011 AT 12:10 AM
Tiny
OBXAUTOMEDIC
  • EXPERT
Here is more info.

A Ford P0171 is a LEAN code for cylinder bank 1, and P0174 is a LEAN code for cylinder bank 2. These codes commonly occur on many Ford vehicles, and are set when the powertrain control module (PCM) sees the air/fuel mixture is running too lean (too much air, not enough fuel).

When the Check Engine Light comes on, either one of these codes, or both, may be found when a code reader or scan tool is plugged into the vehicle diagnostic connector. IF the vehicle is driven long enough, typically both codes will be set.

A P0171 lean code for bank 1 is the cylinder bank on the RIGHT (passenger) side of the engine on Ford vehicles with a V6 or V8 engine and rear-wheel drive.

A P0174 lean code for bank 2 is the cylinder bank on the LEFT (driver) side of the engine on Ford vehicles with a transverse-mounted V6 engine and front-wheel drive. This code is not set on four cylinder engines (no bank 2).

WHAT A LEAN CODE MEANS

A lean fuel condition may exist if the engine is sucking in too much air and/or the fuel system is not delivering enough fuel. If bad enough, a lean fuel condition may cause lean misfire, a rough idle, hesitation or stumble when accelerating, and/or poor engine performance.

Unmetered air can enter the engine through a vacuum leak, a dirty airflow sensor that is not reading airflow accurately, an EGR valve is not closing and is leaking exhaust into the intake manifold, an EGR valve that is allowing too much flow (because the EGR differential pressure sensor that monitors EGR flow is faulty and is under-reporting EGR flow).

If the problem is not enough fuel, the underling cause may be a weak fuel pump, restricted fuel filter, leaky fuel pressure regulator or dirty fuel injectors.

DIRTY MAF SENSOR

One of the most common causes of Ford P0171 and P0174 lean codes is a dirty mass airflow (MAF) sensor. The MAF sensor is located in the air inlet tube
just ahead of the throttle body. The MAF sensor should be protected from outside dust and debris by the air filter, but sometimes the air filter doesn't fit real tight inside the housing and allows unfiltered air into the engine. Dirt can stick to the MAF sensor wire and form a coating that slows the response of the sensor to changes in airflow. The MAF sensor can also be contaminated by fuel vapors that back up through the intake manifold and throttle body when the engine is shut off. The vapors can leave a waxy coating on the sensor wire. This causes the MAF sensor to under report airflow, which in turn misleads the powertrain control module (PCM) so it doesn't add enough fuel to maintain a properly balanced air/fuel ratio. As a result, the engine runs lean and sets a P0171 and/or P0174 code (see Ford TSB 98-23-10 for details).

If the MAF is dirty, the fix is easy enough: just clean or replace the MAF sensor. In many instances, the MAF sensor can be successfully cleaned by spraying the sensor element with electronics cleaner. Do not use any other type of cleaner as this may damage the sensor.

Disconnect the air inlet tube just ahead of the sensor, and then spray the electronics cleaner through the screen at the wire element in the center of the little MAF sensor. Let the cleaner soak in for several minutes, then give it another shot of cleaner. Let it sit another five minutes, then reconnect the air inlet tubing and start the engine.

If the lean codes keep coming back, the MAF sensor may have to be replaced if the engine does not have a vacuum leak or fuel delivery problem.

VACUUM LEAKS

Another common cause of Ford P0171 and P0174 ean codes is an engine vacuum leak. Ford TSB 04-17-4 details procedures for checking fuel trim and looking for vacuum leaks.

On 3.8L Fords with a split-plenum intake manifold, the port gaskets and isolator bolt assemblies for the upper plenum can deteriorate over time and leak air, often as a result of oil being sucked into the intake manifold through the PCV system. Also the vacuum hose that connects the fuel pressure regulator to the intake manifold can swell and leak vacuum where the hose connects to the manifold. Ford TSB 03-16-1 says the fix involves several steps: remove the upper manifold plenum and replace the original gaskets and bolts with revised ones, replace the front valve cover with a revised valve cover that reduces the amount of oil vapor sucked into the PCV system, inspect and replace the fuel pressure regulator hose, and finally, reflash the PCM so it is less sensitive to lean fuel conditions.

BAD DPFE SENSOR

Ford p0171 AND p0174 lean codes can also be set by a bad EGR differential pressure sensor. These sensors have a very high failure rate once a vehicle has more than about 60,000 miles on the odometer or is more than five or six years old.

The DPFE sensor is mounted on the engine, and is attached with two rubber hoses to the tube that routes exhaust gas to the EGR valve. The original equipment sensor has an rectangular aluminum housing about three inches long. Corrosion inside the sensor reduces its sensitivity to EGR flow, causing it to under-report EGR flow. The PCM responds by increasing EGR flow, which may keep the EGR valve open longer than usual creating a lean condition in the engine. Thus, a bad sensor may set a P0401 code (insufficient EGR flow), or it may not set an EGR code but a P0171 and/or P0174 lean code instead.

The cause of the P0401 code in most cases turns out to be a bad DPFE sensor, not an EGR valve problem or an EGR valve that is plugged up with carbon (though this can also set a P0401 code). An aftermarket replacement DPFE sensor costs less than $50 and usually gets rid of not only the P0401 code, but also the P0171 and P0174 codes, too.
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Friday, January 21st, 2011 AT 12:17 AM
Tiny
EXFORD
  • MEMBER
The vacuum leak was found where the tube from the EGR valve goes into the air manifold.A new gasket was put on the tube but it was not tight does vacuum work on the gasket to seal it?
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Sunday, April 10th, 2011 AT 8:51 AM
Tiny
OBXAUTOMEDIC
  • EXPERT
Ok, are you able to post a pic of the leaking area? Please do if you can.

Usually the tube screws into the EGR Valve and into the Manifold and the only gasket is were the EGR Valve bolts to the Intake Manifold.

And No, vacuum does not help in sealing the gasket.
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Sunday, April 10th, 2011 AT 4:41 PM
Tiny
EXFORD
  • MEMBER
I don't know if I did this right but I am trying to send you 2 pics of the area where the problem is.
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Monday, April 11th, 2011 AT 1:27 AM
Tiny
OBXAUTOMEDIC
  • EXPERT
Ok, This has been a problem with the fords and the Plastic Plemun. The plenum gets heated up so many time the plastic starts expanding and creates the leak. The fix is a new plenum either the OE Plastic or find an After Market Aluminum one.
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Monday, April 11th, 2011 AT 2:17 AM
Tiny
EXFORD
  • MEMBER
Where do you find a After market Aluminum one
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Monday, April 11th, 2011 AT 10:37 AM
Tiny
OBXAUTOMEDIC
  • EXPERT
Ok, my mistake they only made aluminum for 95 and earlier. So, looks like you will either need to purchase a new one or see about finding a way to seal that one. And the only way I know would be to use either JB Weld or and Exhaust cement and make sure the tube is square in the hole. It look like it is angled in.
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Monday, April 11th, 2011 AT 1:24 PM

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