The facts : 98 ranger 4.0 4x4 177k

The issue : does the dreaded studder start, check engine light is on saying lean bank 1 bank 2.

Fixes so far: have replaced every gasket from intake base up, alot of new sensors on the intake. All 3 of the 02 sensors new. Have not touched egr. Throughly inspected plenum and intake hose for cracks , no Pitts in intake.

Hopefully you guys can steer me in a direction to fix this , it's a NEBRASKA truck with zero rust. Thought maybe fuel pump might cause all these issues however the turn the key twice trick before starting makes no difference, and I can hear the pump turn on each time I turn the key.

 

Welcome to FTE. You've been busy on this puppy.
Post up All trouble code Number clues.
Good info about replacing the intake gaskets & O2 sensors. Might be helpful to know which other intake, or sensors that have been replaced, chasing the lean both banks code/s. Did the problem come about suddenly after some event???
In 177K miles, have you checked or replaced the PCV valve or its connecting rubber hose or grommets??? They're down stream of & not monitored by the MAF sensor, so if the PCV valve doesn't seat, or its plumbing leaks vacuum, it'll corrupt fuel trim for both cyl banks.
Use your fuel pressure gauge to perform a fuel pressure, bleed down & volume over time tests at the fuel rail Schrader valve test port & post the Numbers.
Fuel pressure should be 64 +/-8psi. It should hold pressure for half an hour or so. Delivery volume should be 1/2pt/15seconds. Fuel pressure can check ok, but if the pump can't supply enough volume, the fuel injectors will give a lean squirt & corrupt fuel trim lean!!!
Smoke test the intake to find leaks. You can do that with a cigar & plastic tubing attached to a convenient intake vacuum port.
Resist tossing any more parts at the problem until you get a positive on your trouble shoot.
Some thoughts for consideration, let us know how it goes.

 

I just purchased this truck approx 1500 miles ago from a guy who was less than honest and hid the fact it failed inspection due to this issue multiple times , though from the maintenance I've seen so far (there hasn't been any) I'll bet it's the original pcv. I did change every vacuum line on the motor at the same time I did the intake gaskets. The codes are P0171 and P0174 . I will do my best to do the fuel tests Saturday and will let you know , thanks , dave

 

OK, good feedback on the previous owners lack of scheduled maintenance. So, if the fuel pressure, or delivery rate aren't right, add a clogged fuel filter to the suspect list.
Once you get the fuel trim problem put right, probably a good idea to continue going through the plugs, wires, filters, fluids & hoses, to bring them up to date on scheduled maintenance, so you know where you are.
Be sure to visit the forum "Tech Info" thread located atop the thread index page, as it has all sorts of helpful wrench turning info. Down in the Miscellaneous section is a link to down load a Owner Manual at no cost if you don't have one, as specified fluids, filters, spark plugs & scheduled maintenance call outs can be found there.
BWD, or Motorcraft parts & fluids are recommended as they've gotten good reports from members.
More thoughts for consideration, keep us posted on your trouble shoot.

 

A faulty fuel injector (twice so far) has caused CEL issues on my 98 (261,500 miles on a bullet proof 3.0). It would start hard and miss on occasion, especially when under a load such as a long hill. As the miss got worse, I got a bank one lean code and a cylinder miss fire. The two codes went away after I finally found and replaced a faulty fuel injector and erased the code. I went through the whole gambit, coil pack, plugs and wires and several sensors before I got it figured out. It did the same thing again about a year later, this time on the other side. I only have 4 more injectors to go.

 

Today I did a few simple tests, first I have a scan tool that has live data and was able to erase the codes before leaving the yard , within 2 miles P0174 appeared as pending then 5 miles later tripped the light , 3 miles after that P0171 was pending and soon after was also a stored code. I pulled over and pinched off the PCV line and repeated the process , no change at all . I do have freeze frame data available if needed.

The other thing I've noticed is, when shifting between gears the engine rpms do not drop when the clutch is pushed , no matter how long u hold it in for , then when the truck has come to a complete stop the rpms stay at 2k for about 15 secs then drops to idle , the live data shows the tps returning to 17.3% as soon as I let off the pedal so I don't think that's this issue , I think it's also being caused by the same thing throwing the codes. Hope this provides something for you guys to go on .

 

On the idle speed, what happens to idle when you disconnect the IAC electrical connector??? If its working, idle speed should drop, the engine may run rough, or stall. It's a common problem part in idle woes. Cleaning doesn't always last, didn't for me but was a good trouble shooting step. If you try cleaning the IAC, use a plastic safe cleaner like CRC MAF sensor spray & keep the IAC electrical connector end elevated, so the solvents & gunk don't run into the solenoid winding area & muck things up, or mess with the wire insulation.
EDIT: What does your scantool show the short & long term fuel trim to be for both cyl banks?
With 177K miles on a questionably maintained engine, have you inspected the throttle plate Edges & bore for deposits, or cleaned them with a coating safe spray???

 

Ok so as for the the intake , lmao the intake was quite filled and caked with debris , looked like greasy carbon , I cleaned what I could without going to metal in fear I might scrape the factory coating off , I'm assuming with fuel trim this is what my meter reads
Stft b1 (%) 1.6
Ltft b1 (%) 25.0
Stft b2 (%) 7.0
Ltft b2 (%) 25.0
Eng rpm 1922
Veh speed 33
Calc load 43.1
Ect 180
That was the read out for P0174

When I unplug tps idle goes up 50 rpm for a sec then returns to normal , when plugged back in zero change
I will check the Iac in the am

 

Ok, good feedback. Bank-2 short term fuel trim looks to be adding more fuel than bank one, so maybe in the near term consider concentrating your trouble shoot there. Long term fuel trim says both banks are adding fuel as both are reading +25% & that's a lot.

If the intake manifold was really gunked up with oily carbon deposits, you likely have a PCV system issue & likely considerable blow by from either worn, or stuck piston rings.

If your scantool will perform a "cylinder balance test", have it do that for additional info to try & focus where to begin your trouble shoot. Then go to any troubled cylinder it flags & check out compression, have a listen to that cylinder fuel injector to determine if it sounds different than the others & check out spark on that cyl.

I'd replace the PCV valve as if its original, its lived two lifetimes & if acting out will mess with fuel trim & not properly vent the crankcase of putrids that cause all kinds of deposit woes.

Ever get around to checking fuel pressure & delivery rate???

 

So today I replaced the PCV, interesting enough the line leading to it was free and clear of any oily deposits, it also made zero difference in the issue , I also took the time to be sure the Iac was working and sure enough it is , and is one of the sensors that was changed.

I can't help but keep wondering though if that egr would cause all these issues?

I did notice today (since the rear end isn't deafening loud anymore) that when flooring the truck in higher gears ( 4-5) the motor pings loudly , suggesting it indeed is running quite lean. In these instances the long term jumps to 25 and short terms are very close at 13.5 and 15.6 .

I am still very lost , my tool does not do a balance test however Sunday when I check the fuel pressure and do the cigar smoke test I'll pull the plugs and do a compression test. I don't believe that's the issue since the truck uses zero oil remarkably.

 

I've seen MAF sensors read low and cause lean conditions, so it's worthwhile to put that on your list to check, too.

 

^+1 on a dirty MAF sensor, as that'll make it slow to react to changes in air flow & that can muck up fuel trim. Slow reacting MAF sorta fits with the fuel trim & ping when you go at throttle up. If you decide to remove & clean it, if just driven, wait until its cooled off & clean it with the non residual CRC MAF sensor spray cleaner, being careful not to touch the heated sensor with the spray wand. Don't touch the cleaned element & keep it squeaky clean when re-installing.
If you find it was dirty, you need to look up stream & find out why it got dirty as its only to see filtered air. So damaged or improperly buttoned up air box, air tube, or air filter, or over oiled cotton gauze or foam air filter, belong on the inspection list.
On the EGR question, since you don't have a trouble code for it, right now I'd leave it lower down on the suspect list, unless you know something about it we don't.
Do a spark plug deposit read, when you do the compression test & let us know what you find.
Be patient & keep up the diagnostic testing & you'll likely find the problem soon.

 

So this weekend I tackled the smoke test. That was an eye opening waste of time lol , zero leaks anywhere , so I decided to go back to basics, compression was equal and within spec , fuel pressure well now that's a new story. Engine off key on : didn't move the needle , at idle 32-34 psi , needless to say I worked my way back to the fuel pump and wouldn't you know it a brand new fuel pump was junk , proud to report now I have 64 psi at idle , the ping is gone , my idle knock has all but gone away and it has what a poorly maintained beat on 177K motor should have for power. And the check engine light is out. Thanks to all for the help.

 

OK, good trouble shooting find, fix, feedback & way to hang in there on your trouble shoot to see it through to a successful ending. Feels good to win one once in a while doesn't it!!!