I have a 2004 Ford F-150 4x4 Supercrew with about 90k miles on it.  I recently noticed a decrease in power and torque from the stop as well as climbing hills.  This weekend on a camping trip I was heading up some mountains and had a significant loss of power as well as rough idling (pulsating and some vibration).  The check engine light came on for about an hour and shut off the next day.  I stopped at Auto Zone for their free diagnostics and even though the light was off, it produced a fault code (printout in the truck right now... I'll get it out and edit my post with the fault code shortly).  Either way, it indicated a Lean mix in bank 1 cylinder 1.  It also suggested that the fault came from either a bad oxygen sensor, a misfire, or a bad injector.  

First, which would be more common?  I've fallen on some hard times and don't have a bunch of money to toss at a ford dealership.  I'd rather pick up a guide for my make/model and do it myself.  I'm guessing O2 sensor but which one?  I know there are a few.  I'm hoping the description of what's going on is enough to narrow the problem down.

Second, would one cylinder without the proper air/fuel ration cause this much power loss.  By "this much" I mean on a dirt road I put the truck in 1st gear and attempted to powerbrake.  No I don't do this regularly, but I figure it's a good judge on how much power/torque I'm getting.  I couldn't even get the rear tires to spin and the engine bogged at about 2300rpm's and wouldn't go any higher.  Anyone have any suggestions/similar experiences?

CMS

The fault code is P0171.  I tried cleaning the mass air flow sensor since there was a little dust in there but it didn't make a difference.  I'm just surprised at the lack of power, which worries me that it could be something a little more serious.  There's also a sucking noise coming from the engine when I punch the gas from idle or accelerate hard.  Could just be the intake but it's pretty loud.

CMS

Sounds like a leaking intake manifold gasket.  Spray starter fluid around suspect areas to identify the vacuum leak.

Would this only affect Cyl 1 if the leak was in that position?  I bought some Electrical Contact Cleaner and I'm cleaning off the mass airflow sensor really well.  If that don't work I'm going to do plugs tomorrow.  I'm at 100k and on the factory plugs, so that's the next step along with a pcv valve.  My worry is the complete loss of power though.  Could all of these items either on their own or added together cause this loss in power?  I'm talking pulling out of a side street I can make a left or right turn and punch it and not even squeal tire....or put the pedal to the floor on a gravel road and not even spin the tires.  I don't feel like I'm tossing money away just because most of what I'll be doing is +/- 90k mile maintanance anyways.  Is it possible to clean an O2 sensor or test one to see if it works or not?  Also, by starter fluid I'm guessing you mean Ether correct?

CMS

Leaking intake manifold.  Confirm this by buying brake clean and spraying on intake manifold while engine is running.  If engine revs up when you spray you have intake issue.

 

Not cylinder one:

 

I have a different type of car but the same exact symptoms. I did the carb cleaner trick on the rubber mannifold and sure enough that was it. It was a easy $50 fix VS $650 the dealer would have gotten me on.

I'll pick some up today and give it a try.  I removed the fittings and cleaned everything up to make sure it has a nice tight seal.  I'm hoping I do find a leak because that's something I can replace on my own for sure.

CMS

Thanks...I'm going to get into it some tonight after work.

CMS

The truck is a newer body style.  I used almost an entire can of starter fluid and didn't come up with anything.  Any other suggestions?  I guess there could still be a vacuum leak somewhere but I don't know how else to find it.  I'm going to get a new set of plugs and try testing my fuel pressure on Wed.  Should I spring for a new MAF Sensor?  The old one looks fine and the two wires are in place and clean.  I'm open to anything.  Ford wants $120 just to pop the hood and so far I've spent $10.  I'm willing to search around for a while.

Something additional I found ...   there was some oil in the intake between the filter/MAF Sensor and the Intake manifold.  It came up the hose that runs between the crank case cover up to the manifold on the drivers side.  Is this typical?

ETA:

Here's a summary of the symptoms again..a little more refined:

-Slow throttle response
-Power / torque loss (more noticable once the engine warms up)
-Loud Hiss before engine RPM increases when revving the engine (not sure if this is normal for the 4.6L or not
-Downshifts on hills and even at high RPM's (4000) it still has no power
-Still have Fault Code P0171: Bank 1 too Lean
-Found no vacuum leaks with starter fluid
-When powerbraking (only to test amount of torque...I don't ever do this) the motor does not produce enough torque to overpower the brakes like it should...boggs at 2000-2300 RPM.

I've already tried:
-Cleaning the MAF Sensor (CRC Electrical Contact Cleaner)
-Checking Vacuum Hoses and Intake Manifold for leaks (found no signs)
-Truck has a new fuel and Air filter



Tonight I'm replacing:
PCV Valve
Oil
Oil Filter
Spark Plugs
and I'm going to try some fuel injector cleaner as well.

I'm still well below what I'd be paying just to get diagnostics done at the dealership...so I'm not complaining.  Again just looking for any suggestions.


CMS

No.



Go buy 3 cans of clorinated brake clean (non-clorinated = non-flamable).  Bank one would be on the passenger side (Quintin say something if I dyslexiated that).  Check the back of the intake, Ford likes to put vacuum lines out of sight, dont ask me why.  The elbow rot out like Quinten said.  Let the engine idle for about 5 - 10 min and then start spraying.  Dont be cheap with the brake clean.  HOSE IT DOWN.  I dont mean all of it in one pull of the trigger but spray it in a good burst.  Pick different sections and work your way from front to back or back to front on the intake manifold.  When the car revs up a bit you are close.

Tried this with ether.  Probably more flamable than brake cleaner and still nothing.  I'll try again though.  What about an O2 sensor?  Any chance that's what it could be?

CMS

An O2 sensor going bad will result in an entire cylinder bank running rich or lean, not an individual cylinder.

Is the P0171 code just one cylinder?  I looked at the print out again and it says bank 1 too lean...but I though I remembered seeing the computer say cylinder one as well.  If it's not a O2 sensor or a vacuum leak what's that leave?

CMS

Please see this post again.  Not one cylinder.

 

I read that and it's why I posed the question, could it be the O2 Sensor, since it would be that entire side of the engine.  I just don't know enough about engines to know what would make all 4 cylinders on that side run lean.  I'll keep looking for a vacuum leak I guess.

Replacing the upstream O2 sensors would be a good idea; they only last about 100k or so before they wear out and slow down or just die completely.

Also, clean any oil out of the MAF sensor.  If you're using a K&N style filter, excess oil can build up on the MAF wires and cause problems.

MAF has already been cleaned.  I'm at 93K so if your estimate is correct it could be the O2 sensor.  I'm going to check for vacuum leaks one more time before buying an O2 sensor by taking the hoses off.  I have an idea on what it would be but I could spend $400 just tossing parts at it.  Didn't find a vacuum leak using starter fluid but I'm going to go back and visually inspect everything better.

CMS

Lean bank one means one of three things:

1 Too much air i.e. vacuum leak and the most common

2 Not enough fuel i.e. low fuel pressure or bad injectors on one bank.  Not likely.  Low fuel pressure would be both banks and for all 4 injectors to go bad at once is not likely at all

3 O2 Sensor not operating correctly and this will have additional codes in the system besides P0171

Thanks.  This helps alot.  Like I said...I don't have the knowledge of engines to be able to do that kind of deductive reasoning.  I'll keep looking for a vacuum leak.  Any other way to find one other than the starter fluid trick?  I was reading around and someone suggested disconnecting something that maintains an idle speed.  Is there anything I'd need to do before trying it again or would the RPM's jump up still without disconnecting anything.

CMS

ETA: I also noticed that the brakes are a little harder to push...so that just reinforces a vacuum leak...but I can't find the darn thing.  I'll keep looking and buy more starter fluid.

What size engine is it?

I had similar problems with my suburban. P0171 and P0174. Replaced MAF sensor, O2 sensors, and stopped using ethanol. Problem solved.

Something I learned on a '87 VW Jetta - squeeze the rubber elbows/ducts to open the cracks you can't see............

Something I learned on a '97 Civic chasing cyl misfire codes - do a compression check before spending money on parts......  I haven't fixed the Civic yet but the 90 psi in cyl 3 is a problem.

Brian

Damn... just damn.

PCV on a my Civic takes a damn contortionist....

Brian

It's a 4.6L.

Well I found part of the problem.  Replaced the spark plugs tonight and on Cyl #'s 3 and 4 the plug was literally less than hand tight.  Cyl 3 was blowing oil out around the plug and burnt the rubber boot on the bottom of the ignition coil.  It still seems to be working fine.  The connection where it goes over the top of the spark plug was fouled pretty bad and I cleaned it up before remounting it.  After I put everything back together I also rechecked the vacuum tubes and still cannot find a leak.  That was definitely messing with my compression.  I believe it still has a vacuum leak but it's running much better.  The truck idles better, has it's power back, and all around just runs smoother.  I'm going to keep looking for a vacuum leak so if I can't find it I'll eventually bring it to a garage, but it's drivable now so that can wait for now if need be.  Either way...thanks for the help guys!

CMS

Check the rest of the plugs, clear the code and drive it to see if it comes back.

I replaced all of them.  Runs good and has more power but I can definitely hear a bad vacuum leak but have no luck finding it at idle.  Becomes very audible from 2000-3000 RPM's in all gears.

CMS