Truck
1999 Ford Ranger
4x4
3.0L V6 Flex Fuel
160000K on the truck, 90k on a new crate motor

So I am throwing the dreaded P0171 & P0174 codes. I have searched far and wide for answers and have tried most of them at this point.
Quick run down
New plugs, wires, egr gasket, valve cover gaskets, intake plenum gasket, pcv valve, all new vacuum lines,
I have also sprayed her down with carb cleaner at various location looking for idle changes, two of the o2 sensors are new 30k ago.

So it only throws the codes at highway speeds. It will never do it during any city driving. It will usually throw the 174 first then both the next time it trips. The truck runs perfectly fine. I have an interface on my phone and pulled this today on it and wanted to get some ideas.

In case picture doesnt post link below.

https://www.ford-trucks.com/forums/a...ctureid=140043

 

Just throwing one out here. Maybe, it's fuel related. Maybe the fuel pump or something can't keep up at highway speeds.

This MIGHT show up if you can read the fuel trims while you're driving. See if the short terms go up around the time you have a problem.

In case you don't know, fuel trims indicate how much the computer adjusts the fuel delivery ( injector pulse width) from the standard table. Short terms are the ones it plays with pretty constantly. Long terms are what they sound like -- an average change based on what's been happening over time.

As for your pic, did you take that when you had a code? Some tests don't run if there's a code or a pending code.

Good Luck,


hj

 

I will check the fuel trims on it. I can see them with the program that i have.

I took that picture right after it threw the codes.

THanks for the help.

 

If you have "lean" codes, the trims are already skewed since that is what the computer uses to set the DTCs. Just looking at them is only going to confirm that they are way off.

"Lean" codes are caused by either too little fuel or too much un-metered air or by a condition that makes the computer think one of those conditions exist.

Look at your MAF data to see if it is rational and close to standard values. A dirty or defective MAF will sometimes this scenario.

A weak fuel delivery due to a weak pump, clogged filter, or restricted fuel line can cause the problem. You can hook up a fuel pressure gauge so that it's visible while driving and monitor it for dropouts or pressure sags.

By far the most common cause of this problem is a leak somewhere in the intake system after the MAF sensor. Spraying flammables around the intake and listening for a change of idle speed is usually useless as the computer corrects things too quickly. Your best bet is to graph, in real time, either the upstream sensors or the short-term fuel trims while making the sprays. If there's an intake leak, the sensors' output or the trim will spike and you can narrow it down that way. Since you have both banks exhibiting the fault codes, it would be in an area that is common to both sides of the engine.

Before doing anything else, you need to pull the freeze frame data so that you understand the specific operating conditions that were present when the codes were set.

 

Ok update on this topic because I still need help.
Heres the updates to the truck
New plugs, wires, egr gasket, valve cover gaskets, intake plenum gasket, pcv valve, all new vacuum lines,
I have also sprayed her down with carb cleaner at various location looking for idle changes, two of the o2 sensors are new 30k ago. Replaced the third o2 sensor about 3 k ago. I also put a new fuel pump in it within 1k. This is all stuff that needed PMing anyways.

So lately the truck has been starting a little hard. She will fire up then die or not quite turn over. Then turning again it will start up.

Could my camshaft position sensor be bad?
Fuel pump relay bad?

 

Sounds like you've done a lot of work.

As Steve mentioned, you could be looking at some sort of MAF issue. Are you able to read live MAF data? Have you tried cleaning the MAF sensor?

I'd still do a fuel pressure test. The acceptable range for your FFV Ranger is 47-63 psi.

Something else to consider is a bad flex-fuel sensor. Maybe it's providing bad information to the PCM. See: Getting Tanked: Flex Fuel Engine Modifications Allow for Alcohol-Based Fuel: Underhood Service

 

So last night went over the intake through the throttle body. Removed everything and cleaned as well as I could including the MAF sensor. I did notice that the bolts on the flange connecting the MAF housing to the air filter box were loose. Hoping this was the issue. Also put in a new fuel pump relay.
So onto the next question. Why do you think I am showing this
https://www.ford-trucks.com/forums/m...0&ref=gnr-prev



Do I not have these points or is there an issue with the emmissions system? How the heck do I post pictures?

 

You need to clear up any pending codes and then complete a "Drive Cycle"

Ford Explorer & Ranger Resource "Serious Explorations"® - View Single Post - drive cycle to clear computer

 

Thanks for the link.

I will do this later today and let you know what I find. I appreciate the help.