1998 Ford Explorer 5.0 v8 p0171 p0174

[andrew 2000 XLT V8]

I have a 98 Ford Explorer XLT 5.0 V8 that has the codes p0171 and p0174 lean on both banks and it is idling really rough and the exhaust sputters. Sometimes won’t go above 2500 rpm runs ok(not great) when driving/ coasting but when I stop if feels like it’s going to stall. I have recently replaced the ignition wires, coil packs, spark plugs, fuel injectors, fuel pressure regulator, all 4 oxygen sensors and the upper intake gaskets(plenum to block, egr housing to plenum, and throttle body to egr housing) problem is still there. I got a smoke test done and shows no vacuum leaks. I am now lost no idea what it could be. Any ideas greatly appreciated

 

[Turdle]

Try disconnecting the maf sensor, then see if it runs a little better.

Does the HVAC blow out of the vents? If it's stuck on defrost vent only, there's your leak.

. Another vacuum leak source is the vacuum brake booster.

 

[andrew 2000 XLT V8]

HVAC blows from vents I'll try unplugging the maf and check the brake booster lines when I get home from work but as I stated I got a smoke check done and there was no vacuum leaks

 

[Turdle]

You might have a weak fuel pump.

Also, a cracked header , or leaked ng egr tube on passenger side will suck unmetered air thru egr. 98 is common for this problem, under the center heat shields

 

[andrew 2000 XLT V8]

You might have a weak fuel pump.

Also, a cracked header , or leaked ng egr tube on passenger side will suck unmetered air thru egr. 98 is common for this problem, under the center heat shields

I was leaning toward fuel pump as well the egr tube was cracked and I replaced it about a year ago I’m not sure about the headers but that would’ve leaked during a smoke test correct?

 

[Turdle]

No, not if egr valve is at rest

 

[Turdle]

I'd try a new fuel filter, then a good fuel pump. No cheapos

 

[andrew 2000 XLT V8]

I was leaning toward fuel pump as well the egr tube was cracked and I replaced it about a year ago I’m not sure about the headers but that would’ve leaked during a smoke test correct? Originally I had 2 misfire codes on cylinder 2 and then 4 but after the injectors those went away but then the lean codes popped up

No, not if egr valve is at rest

That makes sense I saw another thread that said they had the same P0 171 and P0 174 and that the fuel pump fixed it so I think that’s my next thing to replace After I check the brake Booster vacuum lines and the maf sensor

 

[andrew 2000 XLT V8]

I replace the fuel filter about six months ago as well But I’ll probably just put a new one on again when I replace the fuel pump

 

[andrew 2000 XLT V8]

Checked the brake booster lines no vacuum leaks, unplug maf sensor made no difference to rough idle. I replaced the fuel pump this evening and still no difference to the rough idle/ loss of power gonna drive it for a little longer tomorrow to see if any codes pop up since they reset when I disconnected the battery to replace the fuel pump

 

[crunchie_frog]

I would suggest using forscan or other that allows you to see fuel trims at different rpms. If the short term fuel trims go down at higher rpms/load, this means you still have an air leak. Here is pt1 of a video that talks about fuel trims and air leaks and other causes of high fuel trims and lean codes.

 

[410Fortune]

replacing the fuel pump without first testing fuel pressure is silly
Fuel pressure test is REQUIRED when you have lean codes effecting both banks
Yes even with a new pump
If the problem is in the plumbing a new pump will not help

Lean both banks means the computer sees a lean condition on both sides of the engine and has tried to compensate by adding fuel, it was un able to correct the condition. You have either too much un metered air entering the engine/intake after the mas air flow sensor, or you do not have enough fuel able to be delivered, OR some combination of those two

 

[andrew 2000 XLT V8]

I would suggest using forscan or other that allows you to see fuel trims at different rpms. If the short term fuel trims go down at higher rpms/load, this means you still have an air leak. Here is pt1 of a video that talks about fuel trims and air leaks and other causes of high fuel trims and lean codes.

Must still have an air leak somewhere that the shop didn't see during the smoke test. Short term fuel trim for bank 1 was around 7-10% at idle and less than 1% under load bank 2 was at 0% at idle and bounced from 3% to -3% under load

 

[crunchie_frog]

Check the 3/8 vacuum hose that runs out of the intake down under the battery well, at the very lowest point. You may have to remove the battery and battery tray to get to it to remove it and check it thoroughly.

 

[CDW6212R]

If you wonder about a certain vacuum hose, you could run the test again after pinching the hose shut with a proper pinching tool. I have one I got for doing a coolant hose ages ago, it has two flat surfaces in a pliers type of tool. I wouldn't use Vice Grips unless you are expecting to replace the hose.

 

[andrew 2000 XLT V8]

I did a smoke test at home and got smoke coming out of 2 places the top of the iacv and a vacuum line that comes out of the t on the back of the intake plenum. First does the iacv have a blow off valve? Because there seems to be a little valve on top of it second the line that is leaking isn't connected to anything but it has a cap on the end with a spring loaded cap in the center. Is that some kind of vacuum pressure release or should it not be letting air out?

 

[andrew 2000 XLT V8]

I did a smoke test at home and got smoke coming out of 2 places the top of the iacv and a vacuum line that comes out of the t on the back of the intake plenum. First does the iacv have a blow off valve? Because there seems to be a little valve on top of it second the line that is leaking isn't connected to anything but it has a cap on the end with a spring loaded cap in the center. Is that some kind of vacuum pressure release or should it not be letting air out?

Found where the hose was disconnected from so disregard that still not sure about the iacv

 

[410Fortune]

iac has a vent to atmosphere yes

The IAC job is to bypass a small amount of air around the throttle body butterfly in order to control idle speed.
The IAC has a little black cap on top that is a vent


glad you found the disconnected hose on back of intake, that would be a large air leak of un metered air for sure

 

[andrew 2000 XLT V8]

Drove it again and ran live data long term fuel trim is still really high but short term fuel trim is at 0% no vacuum leaks are present but it is still leaning out and idling rough when stopped