So this has been an ongoing issue that started when the temp started dropping below freezing this winter. The truck is a 95 f150 I6 2WD manual trans. What will happen is that when the truck sits over night and the temperature drops below 25 - 30 degrees all night, in the morning i will go out to start it and it will crank and start, rev to about 1500 to 1600 for a second then start dropping to idle but then just keeps dropping till it stalls out. Depending on how cold it gets i will have to restart it a few times to get it to stay idling. Now if i just tried to take off after i got it started it will want to fall on its face if i give it any gas and if i do get it going down the road, as soon as i get around 1500 rpms it will start bucking and choking making it look like its my first time driving a stick.

Now if i let it warm up for say 15 minutes or so it is usually just fine and runs like a champ. If it sits for hours after i turn it off it will start back up just fine. I have the problem when it sits over night. Today it was 15 degrees when i went to start my truck and i had to start it 3 times before it stayed running.

I have been searching this and about every other forum to try and figure out the problem but it seem everyone else has a problem when their truck warms up. I have tried a few things already but nothing REALLY fixes it. It has had a tune up in the past year. Plugs, cap, rotor, fuel filter. It does have the front tank removed. I just recently put a block off plate on the EGR valve but that didn't do much help.

 

Need to pull codes. CEL doesn't have to be on to have codes stored. Sounds like IAC is sticking, not allowing for air to be routed in to help with warm-up, BUT this is just assumption. IAC is your modern day automatic choke, without the need to find a brick to keep the accelerator "Stuck" in that sweet spot, till its warm enough to run.

Pull and Post codes and everyone will chime in.

 

KOEO:
172 Lambda sensor (right) too lean ( have got this one a few other times)
332 EGR valve not opening (Im guessing this has to do with me blocking it off, have never got this one before)

 

I think I'd check fuel pressure first.

These trucks use a powertrain control module that calculates timing, EGR, fuel mixture, and idle speed based on engine temperature, engine load, air temperature, and exhaust gas composition. Until the engine warms up (to 150 degrees Fahrenheit?) they use fixed values for timing, mixture, and idle speed that should allow the engine to run acceptably well for a cold engine. Once warm, the PCM starts calculating and continues to calculate except at wide-open throttle.

Since it seems your truck runs well once warm but has trouble getting there, something in the basics is out of whack. As you've already gone through the ignition, that leaves the fuel system. And since the amount of fuel delivered depends on pulse width to the injector and fuel pressure -- and fuel pressure isn't controlled by the PCM -- it makes hard sense to eliminate fuel pressure as a possibility.

The 4.9L wants 50 to 60 PSI with the engine off and the fuel pump running, as measured on the fuel rail with a fuel pressure tester, 45 to 60 PSI with the engine running, and at least a 5 PSI increase when you remove the vacuum line from the fuel pressure regulator; also, any fuel coming from the FPR vacuum fitting is cause to replace it.

You can also ask the PCM what it thinks is wrong. The procedure is at Fuel Injection Technical Library » How To Run a Self-Test or you can get a code reader from Summit Racing, among others. Your truck is an OBDI variant, so that's the reader you want.

 

Well, your O2 is either really old, staying into the Lean range, exhaust leak near O2 sensor.

Egr vacuum solenoid isn't pulling vacuum for valve. Broken vacuum line, leak in vacuum line, vacuum line not connected, Egr vacuum solenoid not functioning correctly.
That could give Lean condition if vacuum line is broken, leaking or missing. Check vacuum line from Vacuum reservoir on passenger side ( Coffee can)

Can you perform Key On, Engine Running? That may point to your hard starting by checking all sensors, solenoids with Engine running.

 

I was gonna suggest you look at the EGR but if it's blocked off that shouldn't be problem, but whatever you used to block it has to be well sealed.. there cannot be any fresh air getting in except through the throttlebody. If it hasn't been done recently remove the IAC valve and clean it thoroughly, if it's gunked up it'll be sluggish at cold temps and the computer will have trouble controlling idle speed.

 

I have gone over vacuum and have replaced a few lines but that was awhile ago before this had started and I can not find anymore that look bad or even suspicious.

I don't get any codes with key on engine running but on occasion i will get a CEL while i am driving. Doesn't happen all the time but on a few occasions it has happened. One issue I do have is the tube coming off the exhaust for the EGR is broken. Its still in the right place but there are obviously leaks at that point in the exhaust.

 

This is one thing that i have not checked and i know i should have by now but i can't find a fuel pressure tester. Guess I just need to go buy one at this point. As soon I can pull my truck in I will do the self test and see if it pulls anything from that.

 

I have gone through and cleaned all the SHOULD be cleaned parts at this point. It was done about the end of summer. Asking on the forums is about my last resort, I am defiantly not one to just hop on the forums without searching for my issue. I have done EXTENSIVE searching and trouble shooting at this point. I am about to take it to the dealer but I hate not to be able to fix something myself (and don't really want to spend the money).

 

That right there is the most likely cause of your lean code 172. Any exhaust leak upstream of the O2 sensor can and will trigger a lean code. The PCM is dumping in fuel to compensate for a false lean reading from the O2 sensor.

 

The leak is downstream from the O2 sensor. It is the pipe that is in between what looks like the 2 catalytic converters.

 

That is not the EGR pipe, the one that leads down to the converters is for the air injection system. If it is open to the atmosphere then it can draw air into the exhaust and cause the same issue....erroneous lean code.

 

Crap! I'm an idiot. Guess I should have checked a little bit deeper to where that pipe was going. I'm going to go weld that sucker back together and go from there.

 

So I got a fuel pressure gauge and have had it hooked up to my truck for a few days now. I finally dropped back down to -11 last night and went to start my truck and it wouldn't start. I got it running after it died a few times and i was able to look at the fuel pressure gauge before it died again and it was running at 20 psi. After i restarted it again for the third time i checked the fuel pressure and it was running at 45 psi. Would this mean I'm in need of a new fuel pump?

 

Not necessarily. Remove the vacuum hose from the fuel pressure regulator located on the fuel rail. The pressure should go to max (55-60PSI). If it does not then you very well may have a weak fuel pump. If the pressure does increase and stay in the 55-60 PSI range then I would suspect a bad fuel pressure regulator.