ShadeTree55

I am attempting to help a mother of a disabled veteran. Here is the problem. She has a 2003 F150 with 200k miles. It is showing a P0175 code and I cannot find the problem. When I initially started working on the truck it had a lean code on Bank 1. I traced this to a leaking intake gasket. I replaced the gaskets and then began just doing routine maintenance. Changed the plugs. New air and fuel filter, replaced the turn signal switch and some other minor odds and ends. She went to get the truck inspected and it had a pending P0175 code and was rejected. I started trying to find the source. I did a scan and saw that the Long Term fuel trim numbers on Bank 2 were in the -15% range. I went ahead and changed the COPs and the injectors from side to side to see if I could make the problem move. No change. I did a compression test and the numbers were good for all cylinders except 6 and 7 which are about 7% lower than the rest. I checked all vacuum lines, no problems there. I did a vacuum test of the EGR valve and it held a steady vacuum. I've captured the data with my scanner and it looks like the O2 sensors and reporting accurate info. The voltages that are being reported are consistent with a rich condition on Bank 2 and within normal range on Bank 1. I am not real familiar with the 4.6L motor and I am trying to figure out what to do next. The owner is supporting her son and doesn't have much money to spend so I don't want to just throw parts at the problem. Any help or suggestions would be greatly appreciated. John

Jbrew

Sounds like you threw lots of parts at it. Well, coils and injectors is a great update IF you used Motorcraft or Visteon coils.

Your compression test results is a little peculiar. 7% ? Was that a typo ? Are you saying the compression on other cylinders are THAT close ? What were they and how did you test ?

For the 175, pull the PCM fuse or reset the KAM. Sounds like a fluke. Let all monitors complete, force run the EVAP if needed. See if it comes back. It probably won't, get it inspected asa monitors complete.

EDIT:
Also, for the 175, this is a good informational to help with it in case it does come back. Sounds like you like to get to the bottom of things, so this would assist in that, -

http://www.fordscorpio.co.uk/fuelmonitor.htm

A good site ^^ for troubleshooting.

white89gt

I've heard of cracked exhaust manifolds throwing that code. Are there any exhaust leaks prior to the first O2 sensor on the truck?

ShadeTree55

Thank you. I ran the compression test twice. Each time I ran all cylinders with a standard compression gauge with a needle that records the highest reading on that cylinder. After each "dry" test I reran it after adding two tablespoons of oil to determine if there was a different number. I recorded each cylinder value and then averaged the values to determine a baseline. The highest reading on any cylinder was 152 and the lowest was 144. I didn't think of pulling the PCM fuse. What is the KAM? Also, how do you force run the EVAP monitor. I do like to understand why things happen. Since all the cylinders feed off of the throttle body and lower plenum I thought that what is happening has to be related to only bank 2, but that is just an assumption.

ShadeTree55

I have inspected the exhaust manifold and haven't noticed any cracks. I also checked the manifold for temperature at the junction with the head and I didn't see anything that would indicate that there is anything that needs to be further checked.

Jbrew

DTC PO175 by definition is bank 2 (drivers side) related. So your correct if you were questioning.
__________________________

KeepAliveMemory (KAM)

Pulling the PCM fuse, disconnecting the battery for 15 minutes or removing P&N cables from battery and touching them together clears the KAM capacitor. PCM in default, adaptive strategy commences and monitors run to completion or readiness.

To force run a monitor, conditions have to be met. The conditions are outlined at Ford Company Drivecycle...here, -

http://www.obdii.com/drivecycleford.html

____________________________________

Once you reset the KAM, all monitors need to run and complete before you get it inspected or you'll be turned away. You have a scanner correct ? Your scanner should provide monitor information. The EVAP monitor is stubborn or has to wait for proper conditions to run. The link I provided above explains how to shortcut.

Anyway, yea, - reset the KAM by one of the 3 ways I explained above. The PO175 will disappear either temporarily or permanently. It will have to be determined. Once the monitors have all run and are completed, it's ready for inspection as long as you don't have a CEL (MIL).

Frank_Ford

Sorry for the late response but I did not see where you did anything with the MAF sensor and if this gets dirty, your engine will not get the right fuel mixture and you can throw this code. It is really cheap and easy to clean with just a can of MAF cleaner sprayed on the sensor. The cleaner is available at most auto parts stores for less than $10. I have seen truck run much better after doing this maintenance.