Persistent fuel intake problem (P0171)

Ever since I got my 1996 2.4 Tacoma I have been experiencing some problems with the engine sputtering when accelerating or going uphill and sometimes stalling out. Computer read out gives me engine code P0171 Fuel system running lean.
The problems usually start after a long drive especially when it is hot. I read many threads about similar problems and followed the suggestions as much as possible to no avail. This is what I have done so far:

• Replaced fuel pump (twice) and
  
• Replaced fuel filter
• Cleaned out the tank
  
• Checked the fuel lines with compressed air
• Replaced O2 sensor
• Replaced mass air flow sensor
• Checked electrical supply to fuel pump

What else could it be?

 

I'm having a similar problem, have you rebuilt or replaced the injectors?

 

P0171 Fuel system running lean means you more than likely have a vacuum leak. Check all the hoses......

The BEST thing to do is to find someone with a smoke machine and smoke the intake.

 

I had them rebuilt with some injector kit. That did not help either

As in smoke the air intake and see where it comes out?

 

Yes.

 

^THIS

 

A close inspection revealed some kind of leak near the EGR sensor housing
Also I found a crack in the exhaust manifold that was not leaking when running the car for a short while, but might be leaking after a long drive. Could it be partly responsible for the problems I'm having?

 

Depending on the crack, yes.

 

Ok here is an update on the situation. I'll try to be as detailled as possible. First of all you should know that unlike many of you I'm not a (semi) professional mechanic, I did not grow up with a dad who fixed cars of motorcycles and even though over the years I learned quite a bit and fix many things (a Lada does that to you) I'm still as much an amateur on fixing cars as I am on working with Linux (yes I'm eager to learn all kinds of things, but a slow learner). My true profession is philosophy however since I'm not yet ready to live in a cave I started a hotel in rural Panama. A beautiful mountainous area with a pleasant climate and tough roads that are hard on any car.
So I fixed the leak near the EGR sensor, just a warn gasket, and I had the exhaust welded (a temporary fix, if anybody got a spare manifold lying around please let me know)
But the symptoms remained (P0171). So here is what happened last night when driving home form the nearest city.
I started the car and the RPM is too high when running stationary, and fluctuates slightly. The first part of the drive is all flat, yet the engine was having slight sputters here and there. As the road became more hilly, the sputters became slightly worse. Then I got to the steepest part, a 600 foot increase in less than a mile. Many cars have to take it in second, a healthy Tacoma can easily do it in third. To my surprise I made it up in third without a single sputter. But on the next less challenging hill, it almost stalled out.
For 20 minutes after that the car ran as it is supposed too and I could drive like a maniac. Until at a slight hill it again nearly stalled out. By then I was almost home and didn't have any serious trouble.
One more thing, the air-conditioning compressor won't engage anymore. When I turn it on the engine RPM goes up rapidly, then falls flat again. I don't know if this has anything to do with it but I thought I should mention it.
I know its a long shot bu if you see anything unusual on this pic let me know.

 

Still sounds like a vacuum leak. The ecu is excepting a load from the a/c compressor. When ecu doesn't see the idle stay were it should it will drop the idle back down. Different issue then your code.
Do the brakes feel normal.
Does it sound like there's abnormal hissing sound from engine?
Have you compared vacuum diagram on hood to engine? everything is routed correctly?

 

Is that a fuel filter on drivers side by battery? Have you changed the fuel filter underneath the truck?

 

• If you mean the fuel filter in the gas tank, yes that has been changed. The standard fuel filter has been substituted for this inline filter.
• Do the brakes feel normal. Yes
  
• Does it sound like there's abnormal hissing sound from engine? No
  
• Have you compared vacuum diagram on hood to engine? everything is routed correctly? I will have to check

 

Found it! I'm so happy. Thanks to your insistence I did find a vacuum leak on a hard to reach spot of the intake manifold. A big leak too so this must be it! Looks like I can fix this and I'll let you guys know if it does the trick.

 

So the regular fuel filter under the truck (not in tank) has been bypassed?

 

You mean this one?

 

I was cheering too early. I fixed the leak and it runs fine stationary now, but uphill it still stutters badly. And the airco compressor did not engage.

 

Ya that filter. Still has code?

 

Stuttering under load sounds like an ignition problem. wires and sparkplugs are good?

 

Yes, all 2 months old. I didn't get any new codes, but sometimes that takes a while

 

Check coils?