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Discussion Starter #1
MY 96 f150 195k is driving me insane. For example the other day I started it up cold and drove the truck for ½ hour stopping for an hour and restarting. It drove fine. Lot’s of power. I drove around for an hour, stopped to photo engine components for reference and left it idling. Within 5 minutes the idle dropped and it ran rough. Had very little power even to rev the engine. Pulled the Mass Air Flow MAF sensor wire and idle returned to almost normal had power but probably not 100%. At one point it almost stalled. Put MAF back on and it drove like new again? Benn driving it like this for a month. Thanks for any help. I’m out of hair.
 

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Have you taken a good look at the wiring and connector that connects to the MAF sensor to check for loose or broken wires? Have you recently replaced the sensor or have immediate plans to do so? If all that checks out then the computer might be the next place to look since a disconnect/reconnect of a sensor resets the computer.
 

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Discussion Starter #3
Thanks for getting back. The wiring "looks" fine up to where it disappears. I have low fuel pressure in the front tank but the symptoms described are when runing out of the rear. I'm gping to clean the MAF today. The MAF doesn't feed back in any way to fuel delivery does it?
 

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Not really though fuel flow is, of course, controlled by the PCM (Power Control Module) and the MAF tells the PCM how much fuel to deliver. If you haven't already done so, have you checked to see if you have any codes to display? A quick trip to almost any of the larger auto parts chain stores and they can scan your truck. I'd be interested to see if it comes up with anything.

Cleaning the MAF sensor is a good start. When cleaning the sensor, use a good electronics cleaner (though brake cleaner can do the job) and be sure it is dry before you replace it and be careful not to damage it when replacing it.
 

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Discussion Starter #5
I have a reader and for the past year I get 0171 and 0174 out of the front tank and the truck runs with about 90% power. I replaced the fuel filter twice to no effect. The rear tank has always been 100% power and no codes. Just this past summer started this funky running in the rear tank and with the 0171/0174 codes. I don't think I have or can not find a fuel rail pump. The part that drives me nuts is that as long as I drive the truck from start up it runs fine. (This would tell me the mechanics; fuel delivery, are ok). It's only when left to idle or stopped that these symptoms will appear. And the other confusion is that once I pull the MAF for a while when replaced the truck will drive normal for a day or two. Thanks again.
 

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DTC Code: P0171 & 0174
Description: Bank 1 & 2System Too Lean Probable Causes:
  1. Wire harness - Check harness for correct voltage, open, short to ground or short to voltage
  2. Fuel pressure - Pump, regulator, filter or lines
  3. Exhaust leaks or restrictions
  4. Vacuum leaks, damaged hoses or improper routing
  5. Fuel contamination
  6. Sensor not properly installed



Since you're looking at the MAF I'd say you were in the right area to start with. It may be that the sensor is heating up and then giving faulty readings back to the PCM and, as discussed, when you remove it you are essentially resetting the system until it catches up again. At about $74 it isn't a cheap thing to replace but I'd be willing to bet that fixes your issues.
 

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Discussion Starter #7
I cleaned the MAF last week and now the truck seems to run better. Tapping the MAF has no effect on operation. It still takes 3 times to start and you need to keep the idle up or it will stall out in the first minute or so. Funny thing is now it will run out of the front tank where it only bucked and stalled before. But I think this is coincidence. I'm kicking myself for not trying the front tank just before cleaning the MAF . I think I have multiple problems going on here. Thanks again.
 

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Hey kcrawf,

I have and still am going through some of these problems. Check VACUUM LINES. my truck has 115,000 miles with the 300 inline 6 and 5-speed man transmission. i replaced my vacuum lines and egr vavle and now my truck runs great.
my truck was showing 4-5 codes. all the codes were emission related: egr, Oxygen sen bank 1 and 2 (0171 & 0174), and some others. pretty much emission system is ran off the vacuum system in our trucks. so vacuum is what i looked at first. But as i was looking the engine bay over, noticed that someone tried to re-run vacuum lines and did a bad job of it. so i tore all my vacuum lines out and ran new. there will be a sticker on the engine side of your hood with a diagram of the vacuum system that you can reference what is right (u can get bulk hose and a variety pack of fittings at most auto part stores). to get to the vac lines, you will probly have to take the upper intake manifold off. since i had mine off, as a precaution, i replaced the fuel pressure regulator. And now the vacuum lines are ran above the intake manifold now and truck runs/ starts smooth now.

the lean codes i still have and i'm not sure how to fix yet. i cleaned the mass air sensor, have tight connections, hoses & wires. the only thing i can find that throws a flag is my fuel pressure. i checked it and it showed 40 psi. haynes book says it should be 50-60 psi......dont feel like rippin my tank or bed off.... if ya figure out the lean codes, please let me know.:confused:

Got a question for ya. when you start ur truck and it is running smooth (from a cold start) does the truck hickup once you get to or above 3/4 throttle?
 

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Discussion Starter #9
Thanks for this input. Just found out that when it runs "rough" the exhaust is extrememly hot and some friends just tonight told me it is a clogged catalytic converter ($500). They described my problems exactly. Might help. Is your exhaust pipe extremely hot when it runs bad? Food for thought.
 

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Discussion Starter #10
In answer to your last question. when I cold start it it needs to grind longer than normal and I have to blip the throttle for about a minute or so to keep it idling.
 

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Hi, I had a leak in my rear tank and so I recently got it replaced and the garage that did it also replaced the fuel pump. I drove my truck for a couple of days and then it stalled out when I stopped at a stop sign. I managed to restart the engine and it idled low and I had to stay on the gas till I got to where I was going. Then, not five minutes later I tried to start my truck and it tried really hard but it wouldn't turn over. I eventually got it to run, but the battery drained and I had to leave it alone. Since then the truck has been parked in front of my house.

I don't know much about how vehicles work, but it has sat for over two weeks and I am tired of walking everywhere and waiting on other people. If anyone has an idea of what could be wrong with it I would greatly appreciate any suggestions. Thanks!
 

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Katie, when you turn the key to the on position you should hear the fuel pump run for a second or so and then it will be quiet. That is the first thing you need to listen for. The next thing to check is the fuel filter which most people will all but forget about.

The fuel filter for your truck is located amidships on the left frame rail. Be careful when replacing this as there is pressure in the fuel line and that does need to be led before removing the filter!

Start with these two items and if they check out then we'll move on to other items.

Mac
 

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Mac,

Thanks for the reply. The fuel filter checked out clean. My battery is completely drained right now but I have a new one that I am going to throw in later this evening. If that doesn't work then I'm stumped again.

Katie
 

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Sounds like the next thing to do is verify you have the right amount of fuel pressure at the regulator.
 

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Discussion Starter #16
Final result. I had tested the fuel rail pressure at 20-28 psi depending upon tank. I finally replaced the front tank fuel pump, got 45 psi (although I've later heard 35 psi is ok) and the truck runs great. Thank you all for your input. It all lead to success. FYI for those experiencing similar problems.
 

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Glad to hear that! Thanks for the update!

Mac
 

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How would I check the fuel pressure at the regulator? (Where/what is a regulator?) What it's doing now since I replaced the distributor cap is it turns over and it really, really wants to fire but it just isn't starting up. I re-checked my distributor cap to ensure I had all the wires in the right order. It smells like fuel is getting to the engine when I try to start it. Someone thinks the problem could be the timing?
 

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Best bet then is to remove the distributor cap and then rotate the engine to TDC and check to see if the rotor is pointing to the right plug wire. That will confirm that the ignition timing is at least close.
 
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