what would cause a lean mix?

[mach1460]

my code reader tells me that im running too lean, what could cause this, t.p.s? c.p.s? bad o2s? fuel pressure reg? or possible the vacume modulator? haynes is good at telling me what my codes are but not how to fix them very well, i know that it could be a mix of all of these but any one got a suggestion on one that can usually cause it>? thanks!

 

[Opera House]

Any drivability problems?

Knocking on hills, stalling at lights, starting problems and how many miles. I don't trust a fuel pressure regulator this old after my experience but you should have some other symptoms. It would be nice if it was always just one thing that goes bad.

 

[KodeBlu]

Originally posted by mach1460
my code reader tells me that im running too lean, what could cause this? thanks!

Mach1460, I recently had my X scoped because of a CEL. It read codes 171 and 174...engine running too lean. I took it back to Ford and they changed the upper and lower intake manifold gaskets (covered under warranty), because the lower gasket was leaking. I'm thinking that maybe there could be a ongoing problem with the gaskets because when I told the Ford service rep about the problem my X was having, he immediately said that it was probably the lower intake gasket. Hope this helps.

 

[Alec]

Running lean can be caused by many engine and electronic components. I can't really help unless you have more symptoms to report.

 

[MrShorty]

Here's a list of possible causes for a lean condition, other than a bad O2 sensor or bad connection between the O2 sensor and the computer. In essence, anything that would cause there to be too much air and/or not enough fuel.
too much air:

• MAF sensor not correctly measuring the air coming in
• vacuum leak letting in unmetered air

not enough fuel

• low fuel pressure (bad FPR, bad fuel pump, clogged fuel filter)
• clogged injectors not letting fuel into the cylinders

And then there are various sensors that the computer uses to make adjustments to the mixture

• ECT
• IAT
• O2 Sensor

I don't pretend to think that that is a complete list, but it's a list. Many of these things will often cause other symptoms as well (ie. clogged injectors will usually create misfiring cylinders), so any other symptoms you're having may help to narrow it down. Hope this helps.

 

[TPLYNCH]

Aren't the intake manifold bolts on the 1st Gen Ex's notorious for coming loose? Try retorquing the bolts to proper specs and see what happens. Also, check your intake tube to make sure there are no cracks or holes. Won't cost you a thing....

 

[mach1460]

my only symptoms are: roughly 11mpg, starts a little bit hard, im sure of the lean condition cause its got new plus wires clean mas, alot of new sensors, sluggish doesnt seem to pull as hard as it did a month or two ago, my code puller indicated both o2s were indicating a lean condition, those were the only codes except 111 which says o,c,r pass what does that mean??? the other #s for the codes were 172 and 176

 

[MrShorty]

If it were me, I would go to the library and look in a Professional edition manual (My library has Mitchell) and see if that will help in systematically diagnosing the problem.
It appears you've covered a lot of the electronic/computer controls. Have you checked the non-computer related things? (Vacuum leak, intake manifold bolts as mentioned by TPLynch, fuel delivery (Fuel pressure, fuel filter, fuel pump, fuel injectors))