I check the codes.........PO174...& PO170....I can't remember which ones...exactly....anyways Chilton's said "Left bank too lean..." and the other code was "Right bank too lean...".

Sounds like a fuel delivery problem....I just replaced my fuel filter, and threw some fuel system cleaner in their and ran er hard for awhile .......no dice!

Here's the scenario.........My truck runs crappy......at idle......when you get to a red light the truck will idle down sometimes to 500 rpm and "shake" and sometimes dies, however she'll start right back up. A couple of instances it would not start, unless I completely turned the key off for about 10 seconds or so.

The situation only happens like at every other red light........and the longer you drive the worse it gets..........any help would be greatly appreciated......I have a 98 F-150 with 123k, 4x4 w/ 5.4, so I don't want any dealer to tackle this...@ $70 + dollars an hr. for labor ..

 

Not sure about this, but a buddy of mine had what sounds like the same thing happening a couple of weeks back in his 5.4L. Turned out to be a bad coil pack. He unplugged them one at a time till he found one that didn't change the idle and replaced it. Running like a top now.

 

Check for vacuum leaks. The most common is where the hose from your pcv valve where it goes into the back of the throttle body elbow.

If that isn't it try cleaning your MAF sensor.

My freind who works at a Ford dealership says those are the two most common causes that will give you a lean code.

Good luck

Rob

 

I checked the MAF........looks good (clean)......how would I go about checking for vacuum leaks....?/? The only reason I don't think its a vacuum leak is that it doesn't happen at every red light/stop sign. I priced a new IAC from the dealership and its 39.99, not bad, however it looks like a B!tch to get to.

 

Not sure this will help, but I had this exact same code combo (System too Lean Bank 1, System too Lean Bank 2) on my '98 Windstar last year (~60k miles). I just visually inspected all fuel related lines/hoses, in the engine compartment, and found a hole in a rubber elbow that was right on top of the engine. I believe it had something to do with re-introducing unburnt fuel back into the fuel system (total guess there). With the hole in the rubber elbow, it was sucking a bunch of air into the system.

I just bought a $12 elbow/hose assembly and that fixed it. The van also got real bad gas mileage before I fixed it.

Good luck,
greg

 

Easiest way to check for vac. leak is to use carb cleaner or wd 40. with the engine running carefully spray around the manifold, pcv system, egr and the like. If you have a leak it will suck in the spray and change the idle speed.

 

Usually what you see with both sides lean, is un-mettered air getitng into the system or a dirty MAFS.

Visual inspection of the MAFS won't tel you. I use Windex sprayed on a Q-Tip to clean the wire in the barrel in the MAFS. Others complain of this method, but I have never broken it, just be careful when doing it. Usually the dirty MAFS is a combo with pinging. If you are ping free under load, next is vac leaks.

The most common, and hardest to spot is the elbow on the back of the throttle body for the PCV. This is a rubber elbow that can develop hairline cracks, and while a visual inspection makes you think it is ok, replacement of this sub 30.00 part can be the cure.

As for the IAC, yes it is a PITA to replace, but with the codes for both left and right lean being set, I would hold off on replacing the IAC at the moment. The rough idle is usually associated with the IAC, but this is without a DTC set.

Other items to check are the lines on the intake, and the IAT sensor install. Some have changed an air filter, and a bit down the road get a rough idle, and the cause is one of the 2 hoses by the throttle body not being installed correctly. being he cause.
So check all the lines on the intake elbow to see if they are loose, the IAT sensor for it to be fully seated, and the MAFS to the intake elbow mating.

The un-mettered air getting into the system, and the first set of O2 sensors reading lean and reporting back are 90% of the time un-mettered air in the system. The PCM is reading the IAT and lbs/min of air into the system, and then checking on the back side. If the A/F is lean, the pulse width of the injector is increased. If this is done, and the A/F does not match want it should be this is why you are seeing the DTCs you have now ( the PCM notifiying you that this can'`t be. That little air at that high of a temp with that much fuel should be stioch, and it isn't, it is still reading lean no matter what )

After you have removed and re-instaleld all the above items, and replaced the PCV elbow ( complete to PCV is the part from Ford ) then you can go on your way of checking for acracked Vac line, but I would leave that for last right now, and concentrate on checking the intake for leaks of one type or another.

If you search on P017* will produce several posts on the topic, with the soultions that members have had as documentation on the topic.

Good luck, post back what you find.

 

With the engine running take your finger and trace the pcv valve hose to the back of the manifold. You can't see the elbow, but if you have a leak( a good majority of the time you probably will), you will feel a suction with your finger when you place it on the elbow. If so, go to the Ford dealer and get the replacement hose assembly. It costs about $20+ and comes with a new pcv valve.