Hello All,

I have a few questions about my truck:

1994 F150 / EXT. CAB / LONG BOX / 4X4 / 5SPD / 5.0L / DUAL TANK


Things have been getting mighty cold where I am, its been hovering around -30C or -22F. I have noticed my exhaust is incredibly thick, and white while cold. The problem becomes less severe as the engine warms up. The smoke is thickest under acceleration, it's not bad when idling, but if I punch it, I doubt the people behind me can see what is going on.

I had done some research and folks were saying that this is often a case of coolant getting into the combustion chamber, however, I don't recall seeing anything funny about my oil (a milky color or anything of that sort), and I haven't noticed any discoloration in my reservoir or rad.

Recently my gas mileage has been going down a little bit, well, enough for me to notice, and if I run the engine long enough, the engine light comes on, and when doing a KOEO test, I get code 172 (HEGO Indicates lean mixture). I had this problem before, and essentially it was a faulty oxygen sensor always giving a lean reading, so the engine of course tried to compensate with more fuel, leading to bad gas mileage. When I put a new sensor in about a year ago, this code had went away and my mileage increased.

What I am curious is if maybe I need another oxygen sensor, as a result of the decreased mileage, and the engine light.

-Would an excessive mixture mixed with extreme cold cause thick white smoke?
-What would cause a oxygen sensor to fail so prematurely?
-If it's not a sensor, what else can I check to give me a better idea of the problem and its fix?


Also, on a side note. I notice my gas gauge doesn't work anymore for my front tank, but it does for the rear. If I jerk the truck hard enough, I can get the gas gauge to move a little bit. Is this a possible loose connection? Faulty sensor inside the tank?

Thanks guys!

 

I don't remember if your 94 is set up w left / right bank Hego's ?

 

One HEGO. Right after the Y pipe before the cat. So feedback would be from both banks of cylinders.

 

Remembering back to my Chicago days, it seems to me all cars smoked white exhaust when the temps were sub zero. Hell back in the pre fuel injection time, you were luck to get the engines started.

Erase the codes, drive it and see what it says when it gets a little warmer.

 

It's been giving me the code for a while now, the engine needs to run for a decent amount of time however. I notice mine seems to smoke much more than the cars around me though.

 

True dat Uncle Bill! During your Cat's cool down's, the high temp's wick moisture from the cool atmosphere & turns it into steam & dispels it as they re-heat.

Much in the same manner, hot expelled exhaust combines w/ colder moisture laden air as it leaves your tail pipe. This accounts for much of it. Still your question should be, does this account for all of it?

I'm thinking there is a link to you running lean, as that increases you engine temp that much more. Surprised you only have a single code #172 flapping out there by itself.

But when it does (& the senor itself is not suspect) it points to an unmetered intake air source, or a problem w/ the fuel delivery system. Sometimes something as simple as a restricted Fuel filter.

 

I think your explanation confused me a bit. I don't think I understand what it means to "wick" moisture. Could you dumb it down for me

Would the O2 sensor play into this at all, particularly a rich mixture?

 

Think Condensation. Moisture is attracted to heat. Until in the case of water, 212 degrees, it dispels moisture.

Your 02 (if correct) is telling you it would like to be running richer, but that ain't what's happening. It's continuing to run lean for one of two reasons:
1. Too much air
2. Not enough Fuel

The EEC demands an air to fuel ratio of 14.68:1. It won't stop b!tching till it gets it!

 

Maybe this will help:
The balance between condensation and evaporation gives the quantity called vapor partial pressure.
The maximum partial pressure (saturation pressure) of water vapor in air varies with temperature of the air and water vapor mixture. A variety of empirical formulas exist for this quantity; the most used reference formula is the Goff-Gratch equation for the SVP over liquid water below zero degree Celsius:








Where T, temperature of the moist air, is given in units of kelvins, and p is given in units of millibars (hectopascals).
The formula is valid from about −50 to 102 °C; however there are a very limited number of measurements of the vapor pressure of water over supercooled liquid water. There are a number of other formulae which can be used.[9]
Under certain conditions, such as when the boiling temperature of water is reached, a net evaporation will always occur during standard atmospheric conditions regardless of the percent of relative humidity. This immediate process will dispel massive amounts of water vapor into a cooler atmosphere.

(Just "yankin yer chain!" Although correct, it don't mean **** to me either, but it's a slow morning so I thought I'd do a little "cut & paste")

 

You might also check your throttle position sensor. Mine was running rich and the codes said 02 sensor. So I replaced that and noticed the check engine light would come on during acceleration, to the point where my cat converter caught on fire. As luck would have it, I was at the mechanic when it happened, so he ran a voltage test on the tp sensor and found it was faulty.