My check engine light came on about 2 weeks ago, but my car seemed to be running fine so I wasn't too worried about it then me and my friend got his obd scanner and it says banks 1 and 2 are running lean. So we changed my fuel filter, cleaned the maf off with some cleaner, cleared the codes, and checked all the intake lines. The next morning on my way the lights back on again and the idle is real low, especially when I'm in reverse. So does anyone have any ideas on what I should do know, is there any vacuum lines that could be the problem help my truck runs terrible and I drive a lot for work.

 

I'd guess a vacuum leak.

Try this first. Create a small vacuum leak. The rpms should go *UP* if you do that. If they do nothing but go down then I would suspect a leak somewhere else.

Otherwise.. could be the IAC. Have you cleaned it? Sometimes even cleaning them doesn't work. Gotta replace it.

Rich

 

I had a problem with the PCV elbow that connect the PCV tube to the throttle body on the right side near the front of the intake manifold. The rubber gets soft and cracks. My idle was low and slightly rough. It would even die if I let it idle long enough.

I used starter fluid to check for the vacuum leak there and it checked positive for a vacuum leak. The propane method did not work for some reason.

This seems to be a common failure for the 4.0 SOHC engine and a few other Ford engines. It can't hurt to check it out and you may find your problem. It is kind of under the top radiator hose.

 

I also had a check engine light and a code for Right and left bank running lean. I also had a sucking sound when the automatic trans was shifting to
2nd gear. The vacum hose elbow under the radiator hose on the right side had a crack in it. Ford wouldn't sell me just the elbow, so I had to pay $36 for the whole assembly. I wish I would have been a member sooner because it was making noise way before the check engine light came on. It had been into ford for other repairs at least twice and they never caught it.

 

Same thing happened to me but when the dealer told me $36 for the whole assembly, I went home and used a 6 inch piece of 5/8 inch heater hose and a 3 inch piece of smaller diameter vacum hose inside the heater hose so it wouldn't collapse and a hose clamp on each end to make sure it stayed put and no problems since. Thirty six dollars my butt. This is why Ford is in trouble.

 

x2. I had the same problem as the OP, this solved it.

 

make it x3 the cold weather around my area does it, cuz its like 12 degrees F out side

 

X4

I just had the same codes: Banks 1 & 2 running lean. Idle was low. Popped the hood, Used starting fluid to find a small crack in the PCV valve hose right on top of the elbow. Got the $35 dollar part from Ford cuz the back hose was looking ratty too. ;(
Cleared the codes, runs great now.

 

Hi all. I have a beat up 99 4.0 ohv that I just bought. Im not sure I hear the fuel pump when I turn to run. It has trouble starting but revs itself into going. After starting once, it starts much better. Engine runs great at 300k miles. Oh and the truck has a wooden bed. The fuel pump and hoses are a bit exposed.

I also see code for bank 1 being lean and bank 2 pending.

Could they be related?

 

I’d bet money that it’s not a coincidence that both the left AND right bank are running lean. That would mean two problems occurring simultaneously that have the same consequences, the odds of that I’m sure are astronomical (sorry I’m a pharmacist and chemist, my experience with statistics is limited to the 2 semesters required for my undergrad degree). I’m guessing it’s something further upstream, like others have suggested- a vacuum leak perhaps. Maybe it’s a clogged fuel filter or failing fuel pump that’s leading to a lean air/fuel mixture. But I’m thinking it’s more likely on the intake side, ie vacuum leak. My truck is throwing the same codes (p105 and p106?) lean on the left bank and lean on the right bank. I cleared the codes as it seemed to be running ok, so far it hasn’t come back on (approx a week ago).

 

I just had a bank 1 and 2 rich problem on mine. Means both of your o² sensors are picking up a lean condition. Mine turned out to be a badly clogged air filter. I would try and get a fuel pressure gauge. Autozone rents them out for $150 that you get back when your done. Or you can buy one at harbor freight pretty cheap. Check your fuel pressure with key one engine off to begin. Then start the engine and check pressure. After that pull vacuum hose off of the fuel pressure regulator and record that pressure. Finally shut engine off and see if the pressure drops. It shouldn't really drop from what your idle pressure was at could mean fuel is leaking somewhere. This was for the 4.0L OHV. Might be different if you have the SOHC. KOEO pressure should be 35-45psi and idle should be 25-35psi. Pull off vacuum hose should be 35-45psi.
I'd start there if no other trouble codes. Make sure fuel pressure is within spec.

 

i checked fuel pressure. It was 10psi when key at accessory mode, engine off. Started the engine and it went to ~48psi. When the engine was turned off the pressure dropped almost to zero very rapidly. From what I’ve read (hard to tell what’s right on the forums), I should be around 55psi when the engine is idling?... but pressure dropping rapidly seems to point to a failed regulator or gasket somewhere within. I’m hoping anyway - just dropped the fuel tank and changing the pump assembly - prob a bit overkill, but hoping it simplifies install.. if the assembly doesn’t fix it, I suppose next step is fuel injectors?

 

10 psi is definitely too low, gas is leaking somewhere. Either internally or externally. As long as you had a good connection on the fuel rail. Pressure should be at its highest right after the fuel primes to start the engine.engine.if you cant see fuel leaking outside then it could be the fuel regulator. Since it got to 48 psi while running it seems like the fuel pump is fine

 

Maybe there is a way to run a cylinder balance test? I have obd1 truck so I just use a $30 code reader for that test. Not sure how to do it on newer rangers? That would help you rule out fuel injectors.

 

no external leak as far as I can tell. Appreciate the insight!

 

HA! Figures, ‘99 is “newer”.

FYI - This is my first truck/car I’ve worked on, but having a blast. I dunno who else has a 1000LB Bauer torque wrench from harbor freight, but I highly recommend it.

 

New fuel assembly went in. Fuel pressure is up. 55psi at idle. I have no rear shocks or sway bar at the moment so can’t drive to see if the leak codes go away but will let y’all know.

one thing I noticed though was that fuel pressure drops very quickly after spiking when in accessory mode - is that normal? I saw that previously and thought it was a bad regulator.

Hard to say what the starting issue is.. maybe it’s the cold temps as of late or just the 300k miles..

 

yeah, I believe that initial spike is normal when you turn the key on to accessory. Priming the truck for startup.
300k that pretty impressive. Heard these 4.0 ohv engines go that many miles or more. The SOHC engines got us beat on horsepower, but the OHV lasts.

 

she starts like a dream and no sign of running lean, yet.... Only drove ~30 miles so far. Glad I did the fuel pressure test beforehand.

Truck seems to drive/sound a bit stronger. Maybe it’s in my head, haha.

also, I highly recommend changing out the sway bar links and bushings when changing the fuel pump. Driver side link is impossible to remove if the bolt screw is rusted, without moving the tank due to clearance, in my experience. You can only fit a wrench and a long socket doesn’t fit. Truck corners like new




Rust removal and rust reformer

 

Do you have a picture or part # for this part I can't seem to find it anywhere

 

neo16001 hasn't been here for 8 years, so I wouldn't hold my breath waiting for a picture.

 

Does anyone by chance have a pic or part # I recently got my grandpa's old truck and these is the codes that keep popping up it'd be greatly appreciated otherwise I'll try the spray method

 

What codes ?
We need the number and description

We also need to know what you are working on, year and engine.

It would be best if you start your own thread,

 

I have a 98 Ford ranger and it has the same codes PO 171 and 174 bank 1 and 2 running lean and I'm thinking it's this same part alot of you are talking about in this thread but I can't seem to find it anywhere so was hoping there was a part # or picture to help me find the vacuum leak and I can't seem to find where to start a new thread also so sorry about that