Hi y'all,

First off, I own 2002 XLT 3.0 flex with 198 thousand on the dash. I did some minor maintenance such as timing chain w/gasket, water pump w/gasket, oil pan gasket and a few other odds and ins.

Several days after while on my way to work the truck suddenly dies and I'm stuck on the side of the road. I get the truck towed back to the house and from there I start diagnosing.

During those several days there was a code P0174 on the dash because I had yet to reinstall the exhaust from the cat back. After the truck died there was additional code P0171 that appeares.
Obviously lean codes from research.

My problem other than the two codes is the truck is hard to start and when it does, she last literally seconds. Heres where it gets wierd, when i disconnect the idle control valve she runs and will continue intil I turn the key off.

My thought, simple, replace and problem solved. Not the case and hence the reason for the post.

The direction I plan to go unless advised differently is to clean the trottle body and some of its related components. Double and triple check vacuum lines.

Does anyone have any thoughts on this?

 

I'm confused, because the IAC doesn't have the ability to reduce engine speed. Its only purpose is to open and allow the engine to spin faster to control base and fast idle speeds. Like you said - check all the vacuum lines carefully, and any point that might have created a vacuum leak otherwise.

 

Thanks CalebJ for your response. Believe me, I'm as confused as you. All I know is the truck turns over and starts but spits,sputters and jerks as if there's no gas getting to the engine. I do know it is because I put a pressure gauge on the rail and it read 45 psi.

After going over my prior work (maintenance) and looking throughout the engine bay nothing looked out the norm. So I said to myself, let try something because of some readings I've found on the internet about the IAC talking about rough idle, truck completely shutting down, etc. That's when I decided to unplug it and from there the truck started but this time instead of the previous issues it smooth out the idle, despite having lower rpm's. From there I thought the problem was solved and replaced with a new part.

Anyways I will check over the lines here after work and update from there, but I was trying to be hopefully for a quick fix.

 

 

On a FFV, fuel pressure spec is 55 +/- 8psi as I recall. It's definitely lower than all the other engines. If the gauge is off at all, he may be perfectly fine on fuel pressure.

 

Yes, Ford has corrected past 1998 Ranger and up fuel pressure data, currently they say 55psi +/- 8 psi, so basically 45 to 65psi is acceptable, I used to spec 60-65psi as well, but Ford has access to more info than me on long term fuel pressure numbers, so 55psi it is, lol.

And what you get with low fuel pressure are Lean codes on BOTH banks, not a rough running engine, that would come when running pressure was under 15psi most likely

 

Thanks Jeff R 1,

Fuel pump and filter replaced however problem still there. No gas in the damper vacuum line. Was unable to run a pressure test because of the loaner tool borrowed (faulty). I will try again tmrw.

Other than that, still stumbles and stalls, however when I unplug the IAC the rpm's drop to about 5 hundred and it runs smoothly until the key is turn off. Still at a loss to why, but did read some other forums mentioning that if your engine drops the rpms to 5 hundred and stay, its unlikely theres any vacuum leaks.

With that said and if true, thats a plus, however doesnt get me any closer to why I cant start and go.

 

So was able to do a pressure test and got 60psi respectively, however it did take a moment to climb. It wasn't instant like most cases which could of been the pressure gage sealing on the schrader valve. Haven't had good luck with them.

Anyways after I knew the pressure was there I let the truck sit and idle for about 20 min or so. It ran smoother the longer it ran. Thereafter, cleared the codes and shut her down.

The following day I decided it was best to take her out on the road to help with relearning fuel trims. So I jump in and turn the key. Engine cranks over then begins to start and quickly dies. So I turn the key over and listen for the pump and relay. Both sounds are there so I shut off and do it once more before turning the key all the way over.

This time she starts, but runs rough for about the first minute, minute and a half as if the fuel system is pressurizing? After she comes to a smooth idle I take it for a spin. Drive around for about fifteen minutes or so then proceed to the highway.

Once on the inbound ramp I put some pedal into it and to my surprise I get this real quick drag/ governing feeling from the truck. I lift my foot of the gas momentarily while in the process of scaning the dash. No lights, no flashing, nothing. I get back on the pedal softly and throw the hazards on while driving her back onto the side streets.

So again nothing out the normal other than that small hiccup on the highway. While on the side streets I get a idea. How about I put the pedal to the floor from a complete stop. So I did with some short distance and was able to achiveve about 50 mph with rpms as high as 4 grand going 1st thru 4th gears before I was out of pavement and had to let off the gas.

Again nothing abnormal, but not confident I pushed her like I wanted. This time I take her to a stretch of road where no cars would hinder my performance. I I bring the truck to a complete stop and then smash the gas and go.

1st, 2nd , 3rd gear, rpms wrapping upwards to 5 grand. 4th gear about 55 mph and then all of a sudden I get this massive drag/ hesitation. No I dont let of the gas this time, I keep it floored. I look at the dash nothing wierd other than the tach for both the rpms and mph. Best way to decribe them was both seemed to be at there limits. I wasn't gaining speed, nor was the truck shifting off into 5 gear (automatic).

After about a good 30 to 45 seconds I lifted my foot and the truck reved down a bit and also shifted to 5th. I did this experiment once more with identical results.

Any thoughts? Is the still fuel related? I would say so myself, but cant seem to wrap my head around it. The pump I used was a Autobest (F1269) which crossed referenced with Carter (P76538). I wasn't really able to compare the attributes, but I did the Autobest with a Spectrum. With what was listed it looked good. Having a flex fuel system, theres no a huge selection so.

Also on my way into work today, both P0171 and P0174 showed up again.

 

 

it does have a speed limiter that shuts off gas at about 90 and feels like someones riding the brakes.

it almost sounds like its in some sorta limp mode occasionally like its default is to assume the engine is cold and its -50*F outside so it dumps the fuel in trying to warm up the truck.

you didnt damage or forget to plug in either of the coolant temp sensors correct? Have you cleaned the MAF recently? usually theres a way the PCM knows what the incoming intake air is so it knows if its 100*F outside or -10*F outside. Check all the wiring and sensors you removed/unplugged and make sure nothings rubbed thru or melted or grounded to things its not supposed to.

 

Thanks for the response Dngr Rngr,

No the coolant sensor is not unhooked or damaged. None of the wires for that matter look rubbed or damaged. MAF sensor has not been touched reason because of a simple rule I learned sometime ago. If its not broke, don't fix it.

Like previously mentioned, I changed the pump after the truck completely died on me. That was steaming from the P0171 and P0174. Obviously since then I've been able to get it running, but she is still only 60 percent.

I've read numerous post about these codes and it seems as there is never a follow up or the same trails and errors without any promising results.

Basically I had hopes of possible a pin point area but I'm growning tired and dont know if it exists.

 

MAF sensor does get dirty as hell and give false readings. buy a can of the special cleaner only for MAFs from auto parts place and remove it and clean it. Do not touch any of the sensors or thin wires with the straw or your fingers.