Hey i got a '99 with the 4.2L and im having some trouble with it. First, i scanned the check engine light and got back 2 codes, P0171 and p0174. They are lean bank both one and two. Now the problem is my engine has no power in the lower rpm's and i have to drag out each gear (manual trans) to compensate for the bogging down. I have replaced my MAF, fuel filter, plugs and wires a year ago. I pulled the plugs yesterday and they are now fouled due to the engine running lean. It seems that the engine bogs more after it has warmed up also.
In addition, when i press the gas pedal all the way down in lower rpms the engine will bog and i can hear a POP coming from under the hood. After it pops a few times the power will get better. I assume this is backfiring through the intake. Could this be caused from fouled plugs or a bad coil pack or maybe even wires?

ANy help is reallllly appreciated.

 

Check for vacuum leaks. Pay particular attention to the PCV system, follow the hose back from the PCV valve to the intake manifold.

 

Check if your Intake manifold runner control is stuck open.When vacuum is applied to the pot it closes the IMRC butterflys. You should be able to see the two vacuum operated actuators. It's near the center of the intake on the back side. The most common cause of IMRC codes seem to be the clips that hold the control rods on the levers at the ends of the IMRC shafts. You can't check the clips very easily if you don't know what you're looking for because they are in the back. You will be able to see the actuators. There is a steel rod about 1/8" in diameter that comes out of them and connects to a lever on the IMRC shaft. It connects with a little plastic insert. When the insert fails, the rod comes out of the lever and gets jammed. When no movement is detected the PCM thinks it's stuck open. You should also check for vacuum leaks. If you can find the vacuum line that goes to the IMRC actuators you should be able to apply a vacuum and watch them move. If you apply a vacuum and then block the line they should stay where they are. If they bleed down you have a vacuum leak somewhere. I ended up buying some metal clips at Home Depot and replaced the plastic ones. One of my plastic clips were broken and would not hold it in place. If you find that this fixes your problem you will need to clean, re-gap, or replace your plugs. Let us know of your findings

 

Those aren't IMRC codes, they are lean codes.

 

If the clip or clips have fallen out and the position of the butterfly is open you can have a lean condition without having IMRC codes. A big plus is there is no cost to rule this out.

 

and they are now fouled due to the engine running lean.


How are the plugs being fouled if you're running lean? I must be confusing oil fouling with something else.

 

when you foul a plug it is covered in oil residue due to an overly rich mixture. So you cant foul a plug if your running lean.

 

Yes, you can foul a plug by running lean - that causes an overtemp which can loosen any deposits that are in the combustion chamber.

A rich mixture does not leave an oil residue.

 

On 2 stroke dirt bikes if you have an overly rich A/F ratio your bike will run like crap and possibly foul the spark plug. Maybe that is only for 2 strokes, I thought it would be the same concept .

 

Overrich in any engine can foul the plugs. Overrich will only leave oil deposits if it's a 2 stroke. There better not be any oil in the combustion chamber in a 4 stroke, if there is, you have a real problem.