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Running lean

Tiny
VAN ANDERSON
  • MEMBER
  • 1996 FORD F-150
  • 4.9L
  • 6 CYL
  • 2WD
  • MANUAL
  • 249,447 MILES
So I bought my truck back in July and have been trying to figure out why it runs lean. The previous owner never could figure it out and it had been doing it for years. It runs fine all the time but seems a little bit sluggish. If you start it for the first time of the day it starts right up but when you run it for a min and shut it down for about enough time to pump and tank of gas and then start it, it will idle really rough and shake and sputter and sometimes shut off but after a few seconds it levels out. If you run it and let it sit off for an hour or more it will fire right up and run fine. I am at a lost on what to do and need help. Thanks, Van
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Saturday, October 27th, 2018 AT 8:23 PM

18 Replies

Tiny
JACOBANDNICKOLAS
  • MECHANIC
  • 108,133 POSTS
Hi and thanks for using 2CarPros.com.

First, I suggest having the computer scanned to determine if there are diagnostic trouble codes. I am not sure if you have already done that or not, but it would help to know what lean code is stored.

Now, a lean fuel mixture can be caused by a few things. First, and most commonly, is a engine vacuum leak. If unmetered air gets into the combustion chamber, it will cause this.

Here is a link to help determine if there is a leak:

https://www.2carpros.com/articles/how-to-use-an-engine-vacuum-gauge

If you find that is not the problem, next would be fuel pump pressure. Here is a link that discusses how it is checked. The attached picture indicates the manufacturer's recommended pressure specifications.

https://www.2carpros.com/articles/how-to-check-fuel-system-pressure-and-regulator

Check these things first and let me know what you find.

Take care,
Joe
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Sunday, October 28th, 2018 AT 8:09 PM
Tiny
VAN ANDERSON
  • MEMBER
  • 10 POSTS
It does not have a vacuum leak and I think the mechanic said it has got enough fuel pressure but I will check, I cannot remember how many psi he said it had. It has got bank 1 and 2 too lean sensor set off and the evaporative emissions system purge control valve circuit code set off. It has got several of the same codes set off.
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Monday, October 29th, 2018 AT 9:04 AM
Tiny
JACOBANDNICKOLAS
  • MECHANIC
  • 108,133 POSTS
Hi again.

I feel the canister purge solenoid is stuck in the open position. As a result, you have excessive air entering the engine through the intake manifold. Both sides of the engine are lean, so it is one general item causing it. Since you have a code for the purge solenoid, I suspect that is where the problem is coming from. I attached a picture of the component I'm questioning. There is a valve in it which is to open at specific times for a specific amount of time to allow gas fumes from the tank to enter and be burned by the engine. The valve is energized electronically, but if it is stuck open, you are getting too much air.

Take a look at the attached picture.

Let me know what you find,

Joe
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Monday, October 29th, 2018 AT 5:29 PM
Tiny
VAN ANDERSON
  • MEMBER
  • 10 POSTS
I replaced the canister purge valve and reset the codes and it threw the same codes back up and is still running lean. The guys at advanced auto parts said I need to finish a drive cycle so the computer will recognize the new part. Is that right?
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Tuesday, November 6th, 2018 AT 8:55 PM
Tiny
JACOBANDNICKOLAS
  • MECHANIC
  • 108,133 POSTS
Hi again,

Drive it for 50 to 100 miles and reset the light if it does not go off itself. If it comes on again, the problem still exists. At that point, we need to start checking wiring to the solenoid.

Let me know the results.

Take care,
Joe
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Wednesday, November 7th, 2018 AT 4:07 PM
Tiny
VAN ANDERSON
  • MEMBER
  • 10 POSTS
I have cleared my codes and I am waiting to see if they come back. I had a new code show up this time around which I have seen show up before but not often, it is some sort of crankshaft sensor, I will put the picture below. And sometimes it seems like the throttle sticks a little bit. Also I do not have a purge valve solenoid, I am not sure why. And is it worth going ahead and checking both fuel pumps to make sure they are working right?
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Friday, November 9th, 2018 AT 9:22 AM
Tiny
VAN ANDERSON
  • MEMBER
  • 10 POSTS
The codes came back again and it is still running lean on bank 1 and 2 and it still got the evaporative emissions system purge control valve circuit code set off.
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Friday, November 9th, 2018 AT 3:23 PM
Tiny
JACOBANDNICKOLAS
  • MECHANIC
  • 108,133 POSTS
If you are still getting the EVAP code and there are no vacuum leaks, it has to be an electrical issue to the purge valve. Have you checked wiring to the control valve?
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Saturday, November 10th, 2018 AT 6:40 PM
Tiny
VAN ANDERSON
  • MEMBER
  • 10 POSTS
No I have not. Do you have any suggestions on where on the wiring to check first?
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Saturday, November 10th, 2018 AT 9:46 PM
Tiny
JACOBANDNICKOLAS
  • MECHANIC
  • 108,133 POSTS
Just check the plug and make sure there is no corrosion. Follow the wiring to see if it rubbed through or is damaged.
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Sunday, November 11th, 2018 AT 3:35 PM
Tiny
VAN ANDERSON
  • MEMBER
  • 10 POSTS
The wires look fine from what I can see. I am going to check the current and see what it has got. How much current is it suppose to have?
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Wednesday, November 14th, 2018 AT 10:56 AM
Tiny
JACOBANDNICKOLAS
  • MECHANIC
  • 108,133 POSTS
Welcome back:
There will be two wires. One is ground and the other power. You should get battery voltage to it (12v). If you do have battery voltage, supply power to the component to see if you can hear the plunger operating.
Let me know what you find.

Joe
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Wednesday, November 14th, 2018 AT 6:29 PM
Tiny
VAN ANDERSON
  • MEMBER
  • 10 POSTS
I tested the wire and I’m getting current. I also left the purge valve unplugged and it ran great for several days until I filled it up with gas I also had a new code show up. I also talked to the previous owner and his is not sure when the last tune up was done and he said when he put a new coil on the truck it ran perfect for about a week or so and then it started shaking and sputtering again
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Tuesday, November 20th, 2018 AT 10:31 AM
Tiny
JACOBANDNICKOLAS
  • MECHANIC
  • 108,133 POSTS
Are you getting a misfire code? What is the new code?
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Tuesday, November 20th, 2018 AT 7:31 PM
Tiny
VAN ANDERSON
  • MEMBER
  • 10 POSTS
No, I am not getting a misfire. It is catalyst system efficiency below threshold is what it says. P0420
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Wednesday, November 21st, 2018 AT 9:55 AM
Tiny
JACOBANDNICKOLAS
  • MECHANIC
  • 108,133 POSTS
Wow. You are not having luck with this thing. That usually indicates a bad catalytic converter.

I want you to check one more thing for me, the EGR vacuum regulator. Here are the directions.

1. Disconnect battery ground cable.
2. Disconnect the vacuum hoses from the Exhaust Gas Recirculation (EGR) Vacuum Regulator Solenoid.
3. Lightly blow air into the EGR vacuum regulator solenoid and verify that air does not flow through the regulator.
4. Disconnect the electrical connector from the EGR vacuum regulator solenoid.
5. Apply battery voltage and a ground to the electrical connector of the EGR vacuum regulator solenoid.
6. Lightly blow air into the EGR vacuum regulator solenoid and verify that air does blow through the regulator.
7. If air does not flow through the regulator, replace the EGR vacuum regulator solenoid.
8. Connect battery ground cable.

NOTE: When the battery has been disconnected and reconnected, some abnormal drive symptoms may occur until the Power-train Control Module (PCM) relearns its adaptive strategy. The vehicle may need to be driven 16 km (10 miles) or more to relearn the adaptive strategy.

Also, I want you to remove the EGR and inspect both it and the intake for excessive carbon build up. Also, make sure the EGR works when you apply vacuum to it.

1 Disconnect the Exhaust Gas Recirculation (EGR) valve vacuum hose.
2. Disconnect the EGR valve to exhaust manifold tube from EGR valve.
3. Remove EGR valve retainer bolts and EGR valve from upper intake manifold.
4. Remove EGR valve gasket. Clean residue from upper intake manifold gasket surface.

_____________________

Let me know what you find. Also, if I do not hear from you, I hope you have a good Thanksgiving.

Take care,
Joe
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Wednesday, November 21st, 2018 AT 1:35 PM
Tiny
VAN ANDERSON
  • MEMBER
  • 10 POSTS
I will check on that. Could it be oxygen sensors, some sort of idle regulator, or a tune up?
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Sunday, November 25th, 2018 AT 7:07 PM
Tiny
JACOBANDNICKOLAS
  • MECHANIC
  • 108,133 POSTS
Welcome back:

It could be an oxygen sensor, but usually that code leads to the worst possible issue.

Joe
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Sunday, November 25th, 2018 AT 10:27 PM

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