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Just had the heads rebuilt, because of burnt/cupped intake valves on bank 1. Put it all back together and experienced a poor running engine with a P0171/P0174 codes. Found I had some bad injectors, which explained the valve issues. Replaced all the injectors and engine was running well, no codes.
However, after about 65 miles, the P0171 code comes back. I checked for vac leaks, MAF sensor, leaks around the injectors and found nothing. Cleared the codes and drove it again, it drives good, but still will eventually throw a lean code, doesn't happen right away. I have left my reader plugged in and see that I get a soft code first and then later it will light the MIL (could be several miles down the road).
Run a self test and everything checks good. Have cleared codes, but by the end of the day, the lean code will be back. Can you have an intermittently bad component? How the heck to you find it? You can't fix it, if it isn't broke....
Any ideas, would be appreciated. Going to keep driving it to see if what ever is causing the issue will cease to operate all the time.....
Its not a vacuum leak. If it was the long trim would have dropped when you revved it. Try cleaning the MAF with some MAF cleaner, reset the KAM, and drive it for a few miles. Post back with the trims. BTW, your video worked
Its not a vacuum leak. If it was the long trim would have dropped when you revved it. Try cleaning the MAF with some MAF cleaner, reset the KAM, and drive it for a few miles. Post back with the trims. BTW, your video worked
Thanks for the input: I have cleaned the MAF, checked and double checked for vacuum leaks (which you say it isn't and I tend to agree).
I did just replace all eight of my fuel injectors, because of the lean condition. So I have checked to see if they were firing and I can hear each one cycle (hopefully, they are spraying correctly).
Replaced fuel filter, scanner says FPR = 40 psi, holds steady for the most part but have seen it drop to 37 for a couple of seconds than come back up.
As stated before: rebuild heads installed (bank 1 was running lean for a while and I ended up burning/cupping the intake valves on 1, 3 and 4: reason I replaced injectors).
Had exhaust disconnected, so thought this may have been caused by exhaust leak, but don't hear one..... think it is good.
Will go out and reset KAM and drive it for a bit....
Okay, cleared KAM. Drove the truck for 10 miles, stop and go and highway speeds. No codes, running good. Have done this before. Waiting for video to upload so I can post it. However, here are some of the readings that I did have:
Looking like lean condition may have been caused by low fuel pressure. It was reading 37 to 40 psi before, now it doesn't drop below 47 psi and holds pretty steady at 51 to 55 psi. Now the question is: Failing fuel pump or bad signal? Clearing the KAM seems to have brought the pressure up, so will it stay there? Any experience in the fuel pump area? I always thought, they work or they don't work....
Okay, here is the new readings, after clearing KAM and driving 10 miles: Starting to look really hard at the fuel pump pressure as being the problem.....
The long term trim is still too high. How does it run? From the video it sounds like it has good fuel pressure. If it is responsive and has good power I would suspect the MAF is going south. Sometimes cleaning it isn't enough. Also, when was the last time the fuel filter was replaced? How about bad fuel? Filling one up with E85 will do that too. Take a clear bottle and put 1-2 inches of water in it. Make a mark on the bottle where the water line is. Then add the same amount of fuel and shake it up. Once the liquids separate see how far the separation is above the mark. If it close then the fuel is good. If its way above the mark then its E85. The ethanol mixes with the water while the gasoline does not. Once you rule out bad fuel and the filter then I would try a MAF. Get a quality one, preferably OEM.
Fuel filter was changed about 500 miles ago, it was one the first things I changed when this all started.
If MAF was going bad, wouldn't I get a MAF error? What are good reading for long term trim? Is there a way to test the MAF?
I trying to understand how this all works, not just find the problem. Would like to prove the part is bad, prior to replacing it. Not always possible with the limited resources I have, but would like to try.
Thanks, going to run more tests, read some more and see what I can learn.
You want the trims to be as close to 0 as possible. Anything over 10 is a concern. If the maf isn't reading the correct amount of air entering the engine then the trims will be off. Same with the fuel. E85 has maybe 60-70% of the energy as gasoline so if the pcm isnt flex fuel then e85 will make the trims go lean. A vacuum leak will show up as lean trims at idle and close to normal trims at driving rpm because the amount of the leak is a lot less as a percentage of the total airflow while driving. I would test the fuel like I described then if that checks out then I would try a maf. Sometimes when a part is going bad it doesn't set a code, it just goes out of range
Thanks, have been working on this for some time now, trying to make sense of the readings and all that. Really thought the MAF was good, as it was reading, but hadn't seen any way to actually test it without replacement. I don't like to replace parts without having something to justify why I am doing it. However, on your recommendation, I went ahead and got a new MAF. Seems that was the issue, all is running well and I have drove for about 75 miles with no codes.
The idle trims are dead on but the 2000 rpm trims are still a bit too high. Did you get an aftermarket MAF or OEM? I have seen brand new aftermarket mafs not read properly.
Well, you caught me!!! I did get a aftermarket MAF, it was all that was available in "Small Town USA".
New Aftermarket MAF (AutoZone)
Original MAF
Looks like I may have to order a Motorcraft MAF, but which one is the correct one? RockAuto lists two AFLS170RM and AFLS161. Ford Parts says it takes the AFLS170RM, but also has part number 12B579, which fits both numbers in RockAuto.
What should the readings be reading at 2K? Which MAF would you recommend? Or, should I take this one back and say it isn't within specs?
Those are Motorcraft part numbers which cross with the Ford numbers. The 12b579 is the ford base number. The RM means the sensor is a reman. You could see if autozone has a denso or bosch sensor. Those tend to be better than duralast.The trims should be close to 0 in all RPM ranges. Anything over or under 10 indicates a problem,
Those are Motorcraft part numbers which cross with the Ford numbers. The 12b579 is the ford base number. The RM means the sensor is a reman. You could see if autozone has a denso or bosch sensor. Those tend to be better than duralast.The trims should be close to 0 in all RPM ranges. Anything over or under 10 indicates a problem,
You were right!!! LOL
I kept the Duralast MAF in place, to see how it would do. Lasted until today, when I got a bank 1 to lean code. Checked the Long term trim and they were good at idle, but rose higher than before at 2000 RPM.
Just to make a comparison check, I went to AZ on got another Duralast MAF and installed it..... It started out being high at idle and got worse at 2000 RPM. See the video, was taken after clearing KAM and driving about eight miles.
Put the Motorcraft Reman MAF on order from RockAuto today, will see how it works, when it comes in.
