ok, im new to this forum, but in the past i found out that forums can be really helpful, ok so my problem is, i have a 2003 F-150 XLT with a 4.6l in it, and when its idling, is sounds like it have a miss in it it just sits there and putts and shakes likes crazy and acts like it is going to stall out but doesnt, starts up fine and runs fine once you get going down the road, but i scanned it and all it pulled up were codes for o2 sensors running lean and faulty circuit, and nothing for a miss fire, changed the o2 sensors and it didnt do anything and still pulled the codes, im not sure but im thinking it is either the idle air control or the mass air flow sensor??? any ideas, im stumped

 

Welcome to the forums and here is something to check.
PCV valve and line. locate the PCV valve and remove it from the valve cover while the engine is running. You should have vacuum there. Check the elbows and the lines after the PVC valve for deterioration/ cracking. on my truck, the short section of rubber line after the PVC collapsed, makin a hellluva rough idle. also, check all the vacuum lines for leaks. Hope this helps out.

 

You just changed O2 sensors that were doing their job - you probably have a vacuum leak. This will cause a lean condition and your sensors are trying to correct for it and can't quite do it.

Check for vacuum leaks, especially the PCV elbow.

When you have codes, please post the exact codes for assistance, not just what you think they mean..

 

I have a 2000 4.6 f-150 that out of the blue,started stumbling and would not idle and never thru a code and someone on here told me to clean my i.a.c. valve,It took me all of 15 minutes to clean and my truck idles like a champ now!

 

thats what im thinking it is, but how do you clean it, and is there a gasket you have to replace?

anyways no vaccum leaks, pcv is fine, but my codes are P0135 Ho2S11 Heater ckt fault, P0136 Ho2S12 ckt fault, P0156 Ho2S22 ckt fault, P1131 Ho2S11 Snsr indicates lean, and P1151 Ho2S21 Snsr Incidicates lean

 

You could clean it with carb cleaner. Even if you do clean it you will most likely need a new one. I would clean it and if it works buy a new one. Even when cleaned they wont last tooo long its just a temporary thing. I would use a new gasket just to make sure you wont have any leaks.

 

P0135 - Heated O2 Sensor Heater Circuit Malfunction (Bank 1, Sensor 1)

P0156 - Heated O2 Sensor Circuit Malfunction (Bank 2, Sensor 1)

P1131 - Lack Of HO2S11 Switch - Sensor Indicates Lean

P1151 - Lack Of HO2S21 Switch - Sensor Indicates Lean
That's Better.

You have the WRONG O2 sensors in their for one thing IMO. Where did you purchase them from and what kind are they?

How does it idle with a COLD start right after ignition compared to a WARM start? Is there a difference?

 

they are bosch o2 sensors and no it doesnt make a difference wether its warm or cold, still idles like crap

 

I wouldnt use Bosch o2 sensors on these cars. If your going to replace them just buy OE Motorcraft o2 sensors. The Motorcraft sensors have a tighter tolerance / specification. Ive heard a lot of stories with people replacing these sensors with a non OEM part and the codes/problem still exist.

 

Motorcraft doesn't make O2 sensors . Bosch makes them for Ford per spec and they are OEM.

Your confusing O2's w/plugs I think..

 

It's NOT your IAC then. Check your harness . Your codes are telling you what you need to focus on here. If it's not your 02's, then it's either in the wiring or somethings buggy with PCM/Comp. You wouldn't fry an 02 that quick unless your were running rich as hell - that's not the case so locate the correct harness pins , I don't think your getting the voltage down their.

 

Bosch might make them for Ford but the genuine sensor which comes from the factory has tighter tolerances than the Bosch sensor you buy at AutoZone. Even though Bosch might make both; the ones with the stamped "ford" on the shell in the Motorcraft box are better. There have been many other treads on this and in order to save time and a headache i would just spend the cash and get the proper o2 sensor designed for the car.

 

You could be right there. I really haven't heard of any instances or concerns from Bosch 02 replacments. Ford stamp means nothing here - Berg/Warner used a "Ford" Stamp on their sensors - so does NTK. Personally , I haven't had a problem with any of the brands just mentioned. I think I had better mileage with the NTK's - I may re-install those after the winter season..

 

but would the o2 sensors make it idle that bad? they dont do anything until they get to closed loop so when the motor is still cold its ideling like crap so the o2 sensors arent doing anything, im just looking for a solution to the idling problem right now, dont really care about the o2's unless they play a big role in idling

 

That is exactly why I asked you if it idles the same cold vrs. warm ^^ABOVE ^^(read your replies).

You say you "don't care!!" - You will eventually.

Here , I'll post this for someone who might care a little more about this problem . -


TROUBLESHOOTING

Before suspecting the HO2S, the wire connection to the sensor should be checked first. Examine the wires for chafing. Then inspect the connector on the sensor for moisture or damage to the pins. Because the signal voltage is very low (less than 1 volt) the connection is sensitive to damp or poor connection. The heating voltage and current should also be checked and these connections should be clean and bright.

If a careful inspection of the wiring raises no concern log on to the PCM and take a reading of the sensors after warming the engine for at least 3 minutes (to allow closed loop to commence.) Several points should be borne in mind:

1. A sensor should read high (0.6 to 0.9 volts) or low (0.1 to 0.4 volts.) It should never read 0.0 volts.

2. On V engines, do not compare the front sensors together - they will not show the same switching, nor should they - the two Banks of the engine are two separate fuelling cycles.

3. Any sensor showing a negative value (-0.1 to -1 volts) is showing a CSD and the ceramic body has broken. The sensor must be replaced.

4. A Front sensor HO2S11, 21, should be showing a regular 'switch' from high to low, at a frequency of about .7 seconds. Periods of 'flatlining' ie no switching, means that the sensor may be deteriorating and may need to be changed if DTCs are being generated.

5. A front sensor that is not switching may not be faulty, even if DTCs are generated. Check the Long Term Fuel Trims (LTFT) - they may be consistently positive caused by an air leak, or either negative or positive by a faulty fuel pressure regulator, or negative caused by a faulty MAF sensor.

6. A rear sensor HO2S 21, 22, operating correctly on a good catalyst should show a very slow switching.

Heater Circuit Malfunction

Receiving HO2S Heater DT codes P0141/P0161 and P0135/P0155 some additional work can be done to pinpoint the cause. In the event that DTCs demonstrate a concern with more than one heater at the same time then the owner must suspect a wiring rather than a sensor fault. There are only three main splices in the wiring between the PCM and the HO2S heaters and the following diagram will be useful:



Splice A provides the power for both upstream and downstream sensors. A wiring problem with this splice will produce the DTCs P0135/ P0155, P0141/P0161 together, (only 2 of those for four cylinder engines of course.)

Splice B provides the power to the Upstream (front) sensor(s) and generates the DTC P0135/P0155

Splice C provides the power to the downstream sensor(s) and will produce the DTC P0141/P0161