Check Engine light

[Ski]

Aint this a *****? In Feb I had to get my Bronco fixed, spent enough to get it done! Well now my check engine light came back on and apparently the code reads for either; bank one and two O2 sensor, or my MAF. Now someone please tell me why Icant find anything about my MAF in the haynes manual? How can I check it? It started to make a "whistle" as well, that increases in tone as I increase the throttle. Weird huh? Any thoughts????

 

[bidibronco]

A 96 should have the MAF (Mass Air Flow) and it should be at the end of the air tube right next to the air box if I remember correctly. It should be a little aluminum hose connector looking thing with a black thing on top of it with some wires to it. (wow, that sounds complicated) I had one making my car run rich one time so I "adjusted" it to make it run a little leaner. It's not hard to change, you can take off the 3 or 4 screws that hold the black thing down (I think they're star heads) and pull it out. Be careful not to touch the wire that runs between the two little arms because that's what makes the MAF work. The basic concept of the MAF is to read how fast the air is coming into the engine hints the name. Hope this helps a little...

Here's the best I could do to find what a MAF looks like, this is one from summitracing.com

 

[miesk5]

yo,

Do you still have the Codes? if not get it scanned again for free @ AutoZone or AAMCO, etc.

Since you hear a change in noise; suspect an air leak in the MAF area in air tube;

For proper operation, there must be no air leaks.

Check air ducts for damage. Check mounting clamps and o-rings on MAF sensor.

With it running, listen for air leak.

Check MAF sensor wiring.

Check harness and connector for broken wires.

Do you have a K&N filter?; over-oiling could damage MAF.

MAF Contamination TSB 98-23-10 for 94-96 Source: by Ford via miesk5 (Al M) at comcast.net

MAF Servicing TSB 96-22-5 by Ford for 94-96 Source: by Ford via miesk5 (Al M) at comcast.net

MAF



by Tim C

 

[bidibronco]

Your picture is a little better than mine...

 

[Roadkill]

Here is a photo of the one in my '96. I have a K&N. If you have the stock setup, the silver colored part will be connected directly to the air filter box.



Like Miesk says, if you suddenly have a whistle I would suspect an air leak somewhere. "Extra" air entering the system after the Mass Air Sensor would cause the computer to give too little fuel for the amount of air coming in causing a lean burning condition which would, in turn, effect readings at the O2 sensors.

 

[Ski]

Ok so I was looking into what ya'll said and here is what I found. There is a air leak. I am hoping that is the problem and not the Mass Airflow Sensor. But thing is I dont know what this is....... In the pic you will notice an air line that joins...what I will call a T junction.....but only exits on one branch of it. The other exit is open. there was a plug on it with no apparent purpose. That plug had a crack in it and was allowing air to be pulled into it. It is a Vacuum line. I wouild LOVE to know what the purpose is, maybe originally there was something else that it went to???

 

[Seabronc]

If it was capped off with a vacuum cap, replace it. It looks like someone used a T in place of an L fitting for the tight fit there rather than running the hose direct. The whistle would definitely come from a vacuum leak and that will also give a check engine light because it messes up the MAF readings.

Good luck,

>-

 

[Ski]

So Check engine light is still on. Code was read: P0171 and P0174. Any thoughts?

 

[miesk5]

So Check engine light is still on. Code was read: P0171 and P0174. Any thoughts?

yo!

P0171 -System Too Lean (Bank 1) The Adaptive Fuel Strategy continuously monitors fuel delivery hardware. The code is set when the adaptive fuel tables reach a rich calibrated limit. Fuel System:

 

[miesk5]

as Seabronco wrote; someone changed the vac. line or cut it and swapped in da angle fitting; here is your underhood vac diagram from Ford; it shows just that single vac. line from throttle body to vapor management valve

 

[miesk5]

checked my 96 5.0; has that single vac line from TB to the vapor management valve; hose is pre-formed bent rubber line transitioning to a typical Ford plastic line going to the VMV.

 

[Blue beast]

What year is the truck? Clean the maf sensor with CRC mass air sensor cleaner spray it a few 3 second shots let it dry totally then do it again un til the wires are clean. If you run a K&N filter it will gunk up the sensor pretty quick, But even with a paper filter they can get dirty for a number of reasons especially if you don't change the filter as needed for your conditions. Testing your O2 sensors is easy but you need a decent multi meter.

 

[Ski]

Ok so update, I got the check engine light to go out. $120 dollars for a MAP sensor, and $128 dollars for a OBD reader. Now it has started a new problem. hey if its not one thing its another. I turn the key, the engine turns over but doesnt start. This happens about 20% of the time. When it doesnt start I wait a few mins then try again, it usually will start then. The fuel pump is a year old, so I dont think it is that. Your thoughts?????

 

[Broncobill78]

Ok so update, I got the check engine light to go out. $120 dollars for a MAP sensor, and $128 dollars for a OBD reader. Now it has started a new problem. hey if its not one thing its another. I turn the key, the engine turns over but doesnt start. This happens about 20% of the time. When it doesnt start I wait a few mins then try again, it usually will start then. The fuel pump is a year old, so I dont think it is that. Your thoughts?????

The engine needs air, fuel & spark in order to start. If it's not firing then you're missing one of the three, work the problem backwards and figure out which one you're missing. Chances are that it's getting air so now it's narrowed down to fuel or spark. Next time it happens check to see if you have a good spark & then check your fuel pressure, depending on what you find that will lead you to the next branch of the tree.

 

[miesk5]

for now; did you do both the KOER and KOEO tests after the part swap?

eziest ck for now; look at all batty & statrer relay (on passenger side inner fender) connections - + -

if engine does Not turn over well.. does starter/engine seem to spin/turn over as normal?

 

[Ski]

for now; did you do both the KOER and KOEO tests after the part swap?
eziest ck for now; look at all batty & statrer relay (on passenger side inner fender) connections - + -

if engine does Not turn over well.. does starter/engine seem to spin/turn over as normal?

I didnt do any checks like that. Is that the barometeric pressure checks?

The engine turns over well, and starts most of the time. I would say about 98% of the time. the rest of the time that it doesnt start will start after a unspecified period of rest time.

 

[miesk5]

those tests are part of the overall Code Test;

Key On, Engine off (KOEO)

then key on, engine running (KOER)

should be described in your Code Reader Manual

 

[Ski]

those tests are part of the overall Code Test;
Key On, Engine off (KOEO)

then key on, engine running (KOER)

should be described in your Code Reader Manual

Well, the point is mute!!! My check engine light came back on! I have about had it with this thing! Now it is kicking out a fuel lean bank 2 code. You have got to be kidding me. And I think the no start thing is cold cranking AMPs with my battery.

 

[miesk5]

Well, the point is mute!!! My check engine light came back on! I have about had it with this thing! Now it is kicking out a fuel lean bank 2 code. You have got to be kidding me. And I think the no start thing is cold cranking AMPs with my battery.

ok,

This one will be b, but there is info out there;

bank 2 is the cylinder bank on the LEFT (driver) side of the engine

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

P0171 & P0174 Lean Codes by Larry C at AA1Car.com

1. One of the most common causes of Ford P0171 and P0174 lean codes is a dirty mass airflow (MAF) sensor

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

MAF Contamination TSB 98-23-10 by Ford for 94-96

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

btw This TSB 04-17-4 requires a Ford scan tool; so,

Try using carb cleaner around vac hoses/connectors to find a vac leak

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.