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1996 f150 I6 Throwing 9 codes

  #1  
Old 04-24-2018, 07:06 PM
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1996 f150 I6 Throwing 9 codes

So, I am the proud owner of a 1996 f150 i6. I just got my licence a couple of months ago and I drive it back and forth to school. It gets a lot of compliments despite the dents and scratches. Last time I was on here I had a start up issue, you guys helped me figure out it was a broken spark plug (I am very thankful for that). This time I'm here because my truck is throwing some worrisome codes on the OBDII scanner. To keep it short they are: P0174 (system to lean), P0401 (EGR flow insufficient), P1131 (lack of H02511 switch sensor - indicates to lean), P1151 (lack of H02521 switch sensor - indicates to lean), P0301 (cylinder 1 misfire), P0302 (cylider 2 misfire), P0171 (system to lean), P1150 (lack of H02521 switches fuel trim at limit), and P0385 (Crankshaft position sensor B circuit). It usually takes 2 tries to start up, more if its rainy out, so I'm thinking it a vacuum leak somewhere along the air intake. Before I tear apart my manifolds and intakes, I wanted to get your guys opinions. I am by no means a mechanic (I'm not even 18), but I cant stand the thought of giving up and sending it to the shop.
 
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Old 04-24-2018, 08:36 PM
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I'd say a good place to start would be checking fuel pressure at the rail (should be 45-50 psi i think) as well as a compression test on the two cylinders which are misfiring. The lean conditions may indicate a vacuum leak - a good way to test is spraying starting fluid on all the vacuum lines/intake while the truck is running to see if the idle speed picks up. If it does, you found your leak.

I too occasionally get compliments about my '96 F-150 - they really are great old trucks. Pretty easy to work on too.
 
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Old 04-25-2018, 04:46 PM
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P1150 code. Code P1131 very similar to P1150 except Bank 1 on this one.
Faulty Upstream Oxygen Sensor Bank 2, Fuel pressure high or low, MAF sensor dirty/defective, Vacuum leak on engine, Leaking fuel injector or fuel pressure regulator, Faulty Powertrain Control Module (PCM)............I would also check the plugs on 1 and 2 for condition and proper connection and gap.

My 94 and 95 only have one O2 sensor. Not sure about your 96. Sandy
 
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Old 04-25-2018, 09:46 PM
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I've dealt with a few of those codes on my '96 F150 I6 4x4 5spd. Like the others have said, do a fuel pressure test, & check for vacuum leaks first.
I had persistent P0171& P0174 codes until I finally had a shop diagnose it. I did all the basic maintenance items before that. Shop found intake manifold gasket leaking. Replaced upper & lower intake manifold gaskets, seems to be running fine now.
 
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Old 04-26-2018, 06:52 AM
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Its not unusual to get lean codes when you have misfires.
Since the fuel isn't burning you are just pumping air and raw gas through the engine which the O2 sensors see as lean.

Not to say you don't have a vacuum leak, but the lean codes could be just from the misfires - more likely in my opinion.
If you can get a good scanner that allows you to look at the live data you can pin this down pretty quickly, but barring that you can look for clues.

If you have a vacuum leak you would most likely have a high idle. Idle air motor will compensate to some degree for a small leak, but not one big enough to give misfires.
Generally you will also be able to hear the leak if you listen closely. A whistling sound. If you hear one but can't find it, listening through a piece of fuel line or similar large diameter hose a couple feet long helps.
Someone is likely to suggest spraying brake clean around the intake if you believe there is a leak around it, be careful of that as the exhaust and intake are right next to each other on the straight 6, so a definite fire hazard.

You can certainly pull compression on cyl 1 and 2, but I doubt you have suddenly lost compression on 2 cylinders. Still not a bad idea to check as its not impossible, just unlikely, and it might keep you from chasing your tail.

Egr problems are pretty common on these old trucks, but insufficient flow shouldn't cause lean codes or misfires. Something you can deal with later.

The odd bird out here is the crank sensor code. Not sure about the sensor b circuit part right offhand, but generally speaking crank sensors either work or they don't.

However I've seen some things that will cause crank sensor codes without the problem being the sensor itself. Loose mounting bolts, broken mounting tabs, harmonic dampner/reluctor coming apart or loose, and the wires running to the sensor being oil soaked causing them to loose their insulation and shorting, or a corroded connector. Any of these, especially a wiring issue can give you a long crank time, especially in wet weather. Do you have a tach? Have you noticed it acting odd or not working during the long cranking?

Still worth checking fuel pressure - for sure if you have a fuel pressure gauge handy, as it could cause misfires, lean codes, and long crank times as well, but not so much affected by weather. Though shouldn't throw a crank sensor code.

One thing you might try is to cycle the key a couple times without cranking the engine before you crank the engine over. Sometimes when you have a weak fuel pump you can build pressure this way and it will fire right up when you do let it crank. There is also a return check valve in the system, not sure where it is exactly on this year/engine but I think its in the pump itself. If the check valve isn't working it doesn't allow the fuel system to build/hold pressure and cycling the key before you crank it can also get around this. Can also be a clogged fuel filter.

I'd pull 1 and 2 plugs and see what they look like and check for spark, and also have a good look at the crank sensor its connector and wiring and the dampner, along with listening for a vacuum leak.
 
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Old 05-06-2018, 01:01 PM
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Well, I looked pretty hard for a vacuum leak. I took some hose and listened for air. I tightened every bolt I could find along the air intake. Finally, I told my dad it could be the fuel pump. I think it kinda scared him, me working with fuel underneath a 20 year old truck. So, we had it towed to the shop. Turned out it was low fuel pressure due to a bad fuel pump, and a few other minor things. But they found low compression on cylinders 1 and 2. They said its most likely a bad valve, and because of how many miles are on the truck (over 200,000) and because I just drive it back and forth to school, its not worth fixing. I will most likely spray a can of sea foam in there and see if it gets better. So, you guys were right, Thank you, I probably would have still been looking for a vacuum leak if it wasn't for you guys. I still don't know about that crankshaft position sensor code, Ill have to check the codes again. But it starts on the first try and runs fine.
 
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Old 05-06-2018, 05:00 PM
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Originally Posted by GetTheStarterFluid View Post
Well, I looked pretty hard for a vacuum leak. I took some hose and listened for air. I tightened every bolt I could find along the air intake. Finally, I told my dad it could be the fuel pump. I think it kinda scared him, me working with fuel underneath a 20 year old truck. So, we had it towed to the shop. Turned out it was low fuel pressure due to a bad fuel pump, and a few other minor things. But they found low compression on cylinders 1 and 2. They said its most likely a bad valve, and because of how many miles are on the truck (over 200,000) and because I just drive it back and forth to school, its not worth fixing. I will most likely spray a can of sea foam in there and see if it gets better. So, you guys were right, Thank you, I probably would have still been looking for a vacuum leak if it wasn't for you guys. I still don't know about that crankshaft position sensor code, Ill have to check the codes again. But it starts on the first try and runs fine.
Remember to follow the directions on the seafoam product. Watch some videos on how to use it, or you could create more problems. Bummer on the compression, but it could keep running for a long time, you never know.
 
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